Ripple Price Forecast: Has the Much-Awaited XRP Rally Started?

XRP Prices: Patience Is Warranted
2017 was a great year for investors, where the market environment was characterized by a constant barrage of new all-time highs, low volatility, and a number of high-flying sectors taking center stage. 2018 is turning out to be a whole different beast; a market correction has currently gripped the markets and all the high-flying sectors that led the market late last year are currently correcting.

Cryptocurrencies were by far the best-performing asset class last year, and it shouldn’t be too shocking that they are the worst-performing asset class this year. For example, Ripple staged an epic advance in 2017, tacking on an incredible 3,216.67%.

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Ripple Price Forecast: Has the Much-Awaited XRP Rally Started?

Ripple Price Prediction: Q1 Review Shows Korea to Blame for XRP Woes

Ripple News Update
Hopes for an XRP recovery were dashed on Thursday morning as the third-largest cryptocurrency recorded its second consecutive day of losses.

On a more positive note, Ripple was hardly alone. The top 25 cryptocurrencies by market cap plunged as well, with the notable exceptions of TRON and Tether. This downward trend caps off a horrific quarter for XRP prices.

Let’s take a look back over Q1…

At the start of January 2018, the XRP to USD exchange rate reached as high as $3.84. It seems like a distant memory given the bloodbath of the last few months, but it’s important to recap how we arrived at the present situation.

The bearish turn began when.

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Ripple Price Prediction: Q1 Review Shows Korea to Blame for XRP Woes

Cryptocurrency Price Forecast: What You Need to Know This Week

Cryptocurrency Rally Holds Strong
Rallies are important, but holding a rally is even more important.

Thankfully, that’s what cryptocurrencies have done over the last two weeks. Our favorites either stuck close to their previous levels or they exploded to the upside.

Siacoin (SC), for example, rose more than 24% in a single trading session, leading to a cumulative gain of 108% since we first recommended it last month.

Not bad, right? There aren’t too many investments that can boast of triple-digit gains in one month.

Speaking of triple-digit winners, Ethereum (ETH) rose above 100% for the first time in six weeks. It almost erased its gains in early April, but the.

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Cryptocurrency Price Forecast: What You Need to Know This Week

Ecosystem – Wikipedia

This article is about natural ecosystems. For the term used in man-made systems, see Digital ecosystem.

An ecosystem is a community made up of living organisms and nonliving components such as air, water and mineral soil.[3] Ecosystems may be studied either as contingent collections of plants and animals, or as structured systems and communities that are governed by general rules.[4] The biotic and abiotic components interact through nutrient cycles and energy flows.[5] Ecosystems include a network of interactions among organisms, and between organisms and their environment.[6] Ecosystems can be of any size but one ecosystem has a specific, limited space.[7] Some scientists view the entire planet as one ecosystem.[8]

Energy, water, nitrogen and soil minerals are other essential abiotic components of an ecosystem. The energy that flows through ecosystems comes primarily from the sun, through photosynthesis. Photosynthesis also captures carbon dioxide from the atmosphere. Animals also play an important role in the movement of matter and energy through ecoystems. They influence the amount of plant and microbial biomass that lives in the system. As organic matter dies, decomposers release carbon back to the atmosphere. This process also facilitates nutrient cycling by converting nutrients stored in dead biomass back to a form that can be used again by plants and other microbes.[9]

Ecosystems are controlled both by external and internal factors. External factors such as climate, the parent material that forms the soil, topography and time have a big impact on ecosystems, but they are not themselves influenced by the ecosystem.[10] Ecosystems are dynamic: they are subject to periodic disturbances and are in the process of recovering from past disturbances.[11] Internal factors are different: They not only control ecosystem processes but are also controlled by them. Internal factors are subject to feedback loops.[10]

Humans operate within ecosystems. The effects of human activities can influence internal and external factors.[10] Global warming is an example of a cumulative impact of human activities. Ecosystems provide benefits, called “ecosystem services”, which people depend on for their livelihood. Ecosystem management is more efficient than trying to manage individual species.

There is no single definition of what constitutes an ecosystem.[4] German ecologist Ernst-Detlef Schulze and coauthors defined an ecosystem as an area which is “uniform regarding the biological turnover, and contains all the fluxes above and below the ground area under consideration.” They explicitly reject Gene Likens’ use of entire river catchments as “too wide a demarcation” to be a single ecosystem, given the level of heterogeneity within such an area.[12] Other authors have suggested that an ecosystem can encompass a much larger area, even the whole planet.[8] Schulze and coauthors also rejected the idea that a single rotting log could be studied as an ecosystem because the size of the flows between the log and its surroundings are too large, relative to the proportion cycles within the log.[12] Philosopher of science Mark Sagoff considers the failure to define “the kind of object it studies” to be an obstacle to the development of theory in ecosystem ecology.[4]

Ecosystems can be studied through a variety of approachestheoretical studies, studies monitoring specific ecosystems over long periods of time, those that look at differences between ecosystems to elucidate how they work and direct manipulative experimentation.[13] Studies can be carried out at a variety of scales, from microcosms and mesocosms which serve as simplified representations of ecosystems, through whole-ecosystem studies.[14] American ecologist Stephen R. Carpenter has argued that microcosm experiments can be “irrelevant and diversionary” if they are not carried out in conjunction with field studies carried out at the ecosystem scale, because microcosm experiments often fail to accurately predict ecosystem-level dynamics.[15]

The Hubbard Brook Ecosystem Study, established in the White Mountains, New Hampshire in 1963, was the first successful attempt to study an entire watershed as an ecosystem. The study used stream chemistry as a means of monitoring ecosystem properties, and developed a detailed biogeochemical model of the ecosystem.[16] Long-term research at the site led to the discovery of acid rain in North America in 1972, and was able to document the consequent depletion of soil cations (especially calcium) over the next several decades.[17]

The term “ecosystem” is often used very imprecisely and linked with a descriptive term (adjective) even if those systems are rather biomes, not ecosystems.[citation needed] Examples include: terrestrial ecosystem or aquatic ecosystems. Aquatic ecosystems are split into marine ecosystems (Large marine ecosystem is another term used) and freshwater ecosystems.

Ecosystems are controlled both by external and internal factors. External factors, also called state factors, control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem. The most important of these is climate.[10] Climate determines the biome in which the ecosystem is embedded. Rainfall patterns and temperature seasonality determine the amount of water available to the ecosystem and the supply of energy available (by influencing photosynthesis).[10]

Parent material, the underlying geological material that gives rise to soils, determines the nature of the soils present, and influences the supply of mineral nutrients. Topography also controls ecosystem processes by affecting things like microclimate, soil development and the movement of water through a system. This may be the difference between the ecosystem present in wetland situated in a small depression on the landscape, and one present on an adjacent steep hillside.[10]

Other external factors that play an important role in ecosystem functioning include time and potential biota. Similarly, the set of organisms that can potentially be present in an area can also have a major impact on ecosystems. Ecosystems in similar environments that are located in different parts of the world can end up doing things very differently simply because they have different pools of species present.[10] The introduction of non-native species can cause substantial shifts in ecosystem function.

Unlike external factors, internal factors in ecosystems not only control ecosystem processes, but are also controlled by them. Consequently, they are often subject to feedback loops.[10] While the resource inputs are generally controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading.[10] Other factors like disturbance, succession or the types of species present are also internal factors.

Primary production is the production of organic matter from inorganic carbon sources. This mainly occurs through photosynthesis. The energy incorporated through this process supports life on earth, while the carbon makes up much of the organic matter in living and dead biomass, soil carbon and fossil fuels. It also drives the carbon cycle, which influences global climate via the greenhouse effect.

Through the process of photosynthesis, plants capture energy from light and use it to combine carbon dioxide and water to produce carbohydrates and oxygen. The photosynthesis carried out by all the plants in an ecosystem is called the gross primary production (GPP).[18] About 4860% of the GPP is consumed in plant respiration.

The remainder, that portion of GPP that is not used up by respiration, is known as the net primary production (NPP).[19]

Energy and carbon enter ecosystems through photosynthesis, are incorporated into living tissue, transferred to other organisms that feed on the living and dead plant matter, and eventually released through respiration.[19]

The carbon and energy incorporated into plant tissues (net primary production) is either consumed by animals while the plant is alive, or it remains uneaten when the plant tissue dies and becomes detritus. In terrestrial ecosystems, roughly 90% of the net primary production ends up being broken down by decomposers. The remainder is either consumed by animals while still alive and enters the plant-based trophic system, or it is consumed after it has died, and enters the detritus-based trophic system.

In aquatic systems, the proportion of plant biomass that gets consumed by herbivores is much higher.[20] In trophic systems photosynthetic organisms are the primary producers. The organisms that consume their tissues are called primary consumers or secondary producersherbivores. Organisms which feed on microbes (bacteria and fungi) are termed microbivores. Animals that feed on primary consumerscarnivoresare secondary consumers. Each of these constitutes a trophic level.[20]

The sequence of consumptionfrom plant to herbivore, to carnivoreforms a food chain. Real systems are much more complex than thisorganisms will generally feed on more than one form of food, and may feed at more than one trophic level. Carnivores may capture some prey which are part of a plant-based trophic system and others that are part of a detritus-based trophic system (a bird that feeds both on herbivorous grasshoppers and earthworms, which consume detritus). Real systems, with all these complexities, form food webs rather than food chains.[20]

Ecosystem ecology studies “the flow of energy and materials through organisms and the physical environment”. It seeks to understand the processes which govern the stocks of material and energy in ecosystems, and the flow of matter and energy through them. The study of ecosystems can cover 10 orders of magnitude, from the surface layers of rocks to the surface of the planet.[21]

The carbon and nutrients in dead organic matter are broken down by a group of processes known as decomposition. This releases nutrients that can then be re-used for plant and microbial production, and returns carbon dioxide to the atmosphere (or water) where it can be used for photosynthesis. In the absence of decomposition, dead organic matter would accumulate in an ecosystem, and nutrients and atmospheric carbon dioxide would be depleted.[22] Approximately 90% of terrestrial net primary production goes directly from plant to decomposer.[20]

Decomposition processes can be separated into three categoriesleaching, fragmentation and chemical alteration of dead material.

As water moves through dead organic matter, it dissolves and carries with it the water-soluble components. These are then taken up by organisms in the soil, react with mineral soil, or are transported beyond the confines of the ecosystem (and are considered lost to it).[22] Newly shed leaves and newly dead animals have high concentrations of water-soluble components, and include sugars, amino acids and mineral nutrients. Leaching is more important in wet environments, and much less important in dry ones.[22]

Fragmentation processes break organic material into smaller pieces, exposing new surfaces for colonization by microbes. Freshly shed leaf litter may be inaccessible due to an outer layer of cuticle or bark, and cell contents are protected by a cell wall. Newly dead animals may be covered by an exoskeleton. Fragmentation processes, which break through these protective layers, accelerate the rate of microbial decomposition.[22] Animals fragment detritus as they hunt for food, as does passage through the gut. Freeze-thaw cycles and cycles of wetting and drying also fragment dead material.[22]

The chemical alteration of dead organic matter is primarily achieved through bacterial and fungal action. Fungal hyphae produce enzymes which can break through the tough outer structures surrounding dead plant material. They also produce enzymes which break down lignin, which allows them access to both cell contents and to the nitrogen in the lignin. Fungi can transfer carbon and nitrogen through their hyphal networks and thus, unlike bacteria, are not dependent solely on locally available resources.[22]

Decomposition rates vary among ecosystems. The rate of decomposition is governed by three sets of factorsthe physical environment (temperature, moisture and soil properties), the quantity and quality of the dead material available to decomposers, and the nature of the microbial community itself.[23] Temperature controls the rate of microbial respiration; the higher the temperature, the faster microbial decomposition occurs. It also affects soil moisture, which slows microbial growth and reduces leaching. Freeze-thaw cycles also affect decompositionfreezing temperatures kill soil microorganisms, which allows leaching to play a more important role in moving nutrients around. This can be especially important as the soil thaws in the spring, creating a pulse of nutrients which become available.[23]

Decomposition rates are low under very wet or very dry conditions. Decomposition rates are highest in wet, moist conditions with adequate levels of oxygen. Wet soils tend to become deficient in oxygen (this is especially true in wetlands), which slows microbial growth. In dry soils, decomposition slows as well, but bacteria continue to grow (albeit at a slower rate) even after soils become too dry to support plant growth.

Ecosystems continually exchange energy and carbon with the wider environment. Mineral nutrients, on the other hand, are mostly cycled back and forth between plants, animals, microbes and the soil. Most nitrogen enters ecosystems through biological nitrogen fixation, is deposited through precipitation, dust, gases or is applied as fertilizer.[24]

Since most terrestrial ecosystems are nitrogen-limited, nitrogen cycling is an important control on ecosystem production.[24]

Until modern times, nitrogen fixation was the major source of nitrogen for ecosystems. Nitrogen fixing bacteria either live symbiotically with plants, or live freely in the soil. The energetic cost is high for plants which support nitrogen-fixing symbiontsas much as 25% of gross primary production when measured in controlled conditions. Many members of the legume plant family support nitrogen-fixing symbionts. Some cyanobacteria are also capable of nitrogen fixation. These are phototrophs, which carry out photosynthesis. Like other nitrogen-fixing bacteria, they can either be free-living or have symbiotic relationships with plants.[24] Other sources of nitrogen include acid deposition produced through the combustion of fossil fuels, ammonia gas which evaporates from agricultural fields which have had fertilizers applied to them, and dust.[24] Anthropogenic nitrogen inputs account for about 80% of all nitrogen fluxes in ecosystems.[24]

When plant tissues are shed or are eaten, the nitrogen in those tissues becomes available to animals and microbes. Microbial decomposition releases nitrogen compounds from dead organic matter in the soil, where plants, fungi and bacteria compete for it. Some soil bacteria use organic nitrogen-containing compounds as a source of carbon, and release ammonium ions into the soil. This process is known as nitrogen mineralization. Others convert ammonium to nitrite and nitrate ions, a process known as nitrification. Nitric oxide and nitrous oxide are also produced during nitrification.[24] Under nitrogen-rich and oxygen-poor conditions, nitrates and nitrites are converted to nitrogen gas, a process known as denitrification.[24]

Other important nutrients include phosphorus, sulfur, calcium, potassium, magnesium and manganese.[25] Phosphorus enters ecosystems through weathering. As ecosystems age this supply diminishes, making phosphorus-limitation more common in older landscapes (especially in the tropics).[25] Calcium and sulfur are also produced by weathering, but acid deposition is an important source of sulfur in many ecosystems. Although magnesium and manganese are produced by weathering, exchanges between soil organic matter and living cells account for a significant portion of ecosystem fluxes. Potassium is primarily cycled between living cells and soil organic matter.[25]

Biodiversity plays an important role in ecosystem functioning.[27] The reason for this is that ecosystem processes are driven by the number of species in an ecosystem, the exact nature of each individual species, and the relative abundance organisms within these species.[28] Ecosystem processes are broad generalizations that actually take place through the actions of individual organisms. The nature of the organismsthe species, functional groups and trophic levels to which they belongdictates the sorts of actions these individuals are capable of carrying out, and the relative efficiency with which they do so.

Ecological theory suggests that in order to coexist, species must have some level of limiting similaritythey must be different from one another in some fundamental way, otherwise one species would competitively exclude the other.[29] Despite this, the cumulative effect of additional species in an ecosystem is not linearadditional species may enhance nitrogen retention, for example, but beyond some level of species richness, additional species may have little additive effect.[28]

The addition (or loss) of species which are ecologically similar to those already present in an ecosystem tends to only have a small effect on ecosystem function. Ecologically distinct species, on the other hand, have a much larger effect. Similarly, dominant species have a large impact on ecosystem function, while rare species tend to have a small effect. Keystone species tend to have an effect on ecosystem function that is disproportionate to their abundance in an ecosystem.[28] Similarly, an ecosystem engineer is any organism that creates, significantly modifies, maintains or destroys a habitat.

Ecosystems are dynamic entities. They are subject to periodic disturbances and are in the process of recovering from some past disturbance.[11] When a perturbation occurs, an ecoystem responds by moving away from its initial state. The tendency of an ecosystem to remain close to its equilibrium state, despite that disturbance, is termed its resistance. On the other hand, the speed with which it returns to its initial state after disturbance is called its resilience.[11] Time plays a role in the development of soil from bare rock and the recovery of a community from disturbance.[10]

From one year to another, ecosystems experience variation in their biotic and abiotic environments. A drought, an especially cold winter and a pest outbreak all constitute short-term variability in environmental conditions. Animal populations vary from year to year, building up during resource-rich periods and crashing as they overshoot their food supply. These changes play out in changes in net primary production decomposition rates, and other ecosystem processes.[11] Longer-term changes also shape ecosystem processesthe forests of eastern North America still show legacies of cultivation which ceased 200 years ago, while methane production in eastern Siberian lakes is controlled by organic matter which accumulated during the Pleistocene.[11]

Disturbance also plays an important role in ecological processes. F. Stuart Chapin and coauthors define disturbance as “a relatively discrete event in time and space that alters the structure of populations, communities and ecosystems and causes changes in resources availability or the physical environment”.[30] This can range from tree falls and insect outbreaks to hurricanes and wildfires to volcanic eruptions. Such disturbances can cause large changes in plant, animal and microbe populations, as well soil organic matter content.[11] Disturbance is followed by succession, a “directional change in ecosystem structure and functioning resulting from biotically driven changes in resources supply.”[30]

The frequency and severity of disturbance determines the way it impacts ecosystem function. Major disturbance like a volcanic eruption or glacial advance and retreat leave behind soils that lack plants, animals or organic matter. Ecosystems that experience such disturbances undergo primary succession. Less severe disturbance like forest fires, hurricanes or cultivation result in secondary succession and a faster recovery.[11] More severe disturbance and more frequent disturbance result in longer recovery times.

Classifying ecosystems into ecologically homogeneous units is an important step towards effective ecosystem management.[31] There is no single, agreed-upon way to do this. A variety of systems exist, based on vegetation cover, remote sensing, and bioclimatic classification systems.[31]

Ecological land classification is a cartographical delineation or regionalisation of distinct ecological areas, identified by their geology, topography, soils, vegetation, climate conditions, living species, habitats, water resources, and sometimes also anthropic factors.[32]

Human activities are important in almost all ecosystems. Although humans exist and operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.[10]

Ecosystems provide a variety of goods and services upon which people depend.[33] Ecosystem goods include the “tangible, material products” of ecosystem processes such as food, construction material, medicinal plants.[34] They also include less tangible items like tourism and recreation, and genes from wild plants and animals that can be used to improve domestic species.[33]

Ecosystem services, on the other hand, are generally “improvements in the condition or location of things of value”.[34] These include things like the maintenance of hydrological cycles, cleaning air and water, the maintenance of oxygen in the atmosphere, crop pollination and even things like beauty, inspiration and opportunities for research.[33] While ecosystem goods have traditionally been recognized as being the basis for things of economic value, ecosystem services tend to be taken for granted.[34]

When natural resource management is applied to whole ecosystems, rather than single species, it is termed ecosystem management.[35] Although definitions of ecosystem management abound, there is a common set of principles which underlie these definitions.[36] A fundamental principle is the long-term sustainability of the production of goods and services by the ecosystem;[36] “intergenerational sustainability [is] a precondition for management, not an afterthought”.[33]

While ecosystem management can be used as part of a plan for wilderness conservation, it can also be used in intensively managed ecosystems[33] (see, for example, agroecosystem and close to nature forestry).

As human populations and per capita consumption grow, so do the resource demands imposed on ecosystems and the impacts of the human ecological footprint. Natural resources are vulnerable and limited. The environmental impacts of anthropogenic actions are becoming more apparent. Problems for all ecosystems include: environmental pollution, climate change and biodiversity loss. For terrestrial ecosystems further threats include air pollution, soil degradation, and deforestation. For aquatic ecosystems threats include also unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollution, microplastics pollution, water pollution, and building on coastal areas.[37]

Society is increasingly becoming aware that ecosystem services are not only limited, but also that they are threatened by human activities. The need to better consider long-term ecosystem health and its role in enabling human habitation and economic activity is urgent. To help inform decision-makers, many ecosystem services are being assigned economic values, often based on the cost of replacement with anthropogenic alternatives. The ongoing challenge of prescribing economic value to nature, for example through biodiversity banking, is prompting transdisciplinary shifts in how we recognize and manage the environment, social responsibility, business opportunities, and our future as a species.[citation needed]

The term “ecosystem” was first used in 1935 in a publication by British ecologist Arthur Tansley.[fn 1][38] Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment.[39] He later refined the term, describing it as “The whole system, … including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment”.[40] Tansley regarded ecosystems not simply as natural units, but as “mental isolates”.[40] Tansley later defined the spatial extent of ecosystems using the term ecotope.[41]

G. Evelyn Hutchinson, a limnologist who was a contemporary of Tansley’s, combined Charles Elton’s ideas about trophic ecology with those of Russian geochemist Vladimir Vernadsky. As a result he suggested that mineral nutrient availability in a lake limited algal production. This would, in turn, limit the abundance of animals that feed on algae. Raymond Lindeman took these ideas further to suggest that the flow of energy through a lake was the primary driver of the ecosystem. Hutchinson’s students, brothers Howard T. Odum and Eugene P. Odum, further developed a “systems approach” to the study of ecosystems. This allowed them to study the flow of energy and material through ecological systems.[39]

See more here:

Ecosystem – Wikipedia

FintruX – The Global P2P Lending Ecosystem

Chairman of the Board Yew Poh Leong

YP grew Dun & Bradstreet Software from 15 to over 250 employees as a managing director in Asia. He has provided business solutions and services to well-known corporations including Telekom Malaysia, Hong Kong Telecom, PLDT, Communications Authority of Thailand, Shell, Prudential, AIG, Starwood, Minolta, National Panasonic, Sony, Aiwa, Standard Chartered Bank, Malayan Banking, Bank of China, etc.

Read this article:

FintruX – The Global P2P Lending Ecosystem

Ecosystem – Wikipedia

This article is about natural ecosystems. For the term used in man-made systems, see Digital ecosystem.

An ecosystem is a community made up of living organisms and nonliving components such as air, water and mineral soil.[3] Ecosystems may be studied either as contingent collections of plants and animals, or as structured systems and communities that are governed by general rules.[4] The biotic and abiotic components interact through nutrient cycles and energy flows.[5] Ecosystems include a network of interactions among organisms, and between organisms and their environment.[6] Ecosystems can be of any size but one ecosystem has a specific, limited space.[7] Some scientists view the entire planet as one ecosystem.[8]

Energy, water, nitrogen and soil minerals are other essential abiotic components of an ecosystem. The energy that flows through ecosystems comes primarily from the sun, through photosynthesis. Photosynthesis also captures carbon dioxide from the atmosphere. Animals also play an important role in the movement of matter and energy through ecoystems. They influence the amount of plant and microbial biomass that lives in the system. As organic matter dies, decomposers release carbon back to the atmosphere. This process also facilitates nutrient cycling by converting nutrients stored in dead biomass back to a form that can be used again by plants and other microbes.[9]

Ecosystems are controlled both by external and internal factors. External factors such as climate, the parent material that forms the soil, topography and time have a big impact on ecosystems, but they are not themselves influenced by the ecosystem.[10] Ecosystems are dynamic: they are subject to periodic disturbances and are in the process of recovering from past disturbances.[11] Internal factors are different: They not only control ecosystem processes but are also controlled by them. Internal factors are subject to feedback loops.[10]

Humans operate within ecosystems. The effects of human activities can influence internal and external factors.[10] Global warming is an example of a cumulative impact of human activities. Ecosystems provide benefits, called “ecosystem services”, which people depend on for their livelihood. Ecosystem management is more efficient than trying to manage individual species.

There is no single definition of what constitutes an ecosystem.[4] German ecologist Ernst-Detlef Schulze and coauthors defined an ecosystem as an area which is “uniform regarding the biological turnover, and contains all the fluxes above and below the ground area under consideration.” They explicitly reject Gene Likens’ use of entire river catchments as “too wide a demarcation” to be a single ecosystem, given the level of heterogeneity within such an area.[12] Other authors have suggested that an ecosystem can encompass a much larger area, even the whole planet.[8] Schulze and coauthors also rejected the idea that a single rotting log could be studied as an ecosystem because the size of the flows between the log and its surroundings are too large, relative to the proportion cycles within the log.[12] Philosopher of science Mark Sagoff considers the failure to define “the kind of object it studies” to be an obstacle to the development of theory in ecosystem ecology.[4]

Ecosystems can be studied through a variety of approachestheoretical studies, studies monitoring specific ecosystems over long periods of time, those that look at differences between ecosystems to elucidate how they work and direct manipulative experimentation.[13] Studies can be carried out at a variety of scales, from microcosms and mesocosms which serve as simplified representations of ecosystems, through whole-ecosystem studies.[14] American ecologist Stephen R. Carpenter has argued that microcosm experiments can be “irrelevant and diversionary” if they are not carried out in conjunction with field studies carried out at the ecosystem scale, because microcosm experiments often fail to accurately predict ecosystem-level dynamics.[15]

The Hubbard Brook Ecosystem Study, established in the White Mountains, New Hampshire in 1963, was the first successful attempt to study an entire watershed as an ecosystem. The study used stream chemistry as a means of monitoring ecosystem properties, and developed a detailed biogeochemical model of the ecosystem.[16] Long-term research at the site led to the discovery of acid rain in North America in 1972, and was able to document the consequent depletion of soil cations (especially calcium) over the next several decades.[17]

The term “ecosystem” is often used very imprecisely and linked with a descriptive term (adjective) even if those systems are rather biomes, not ecosystems.[citation needed] Examples include: terrestrial ecosystem or aquatic ecosystems. Aquatic ecosystems are split into marine ecosystems (Large marine ecosystem is another term used) and freshwater ecosystems.

Ecosystems are controlled both by external and internal factors. External factors, also called state factors, control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem. The most important of these is climate.[10] Climate determines the biome in which the ecosystem is embedded. Rainfall patterns and temperature seasonality determine the amount of water available to the ecosystem and the supply of energy available (by influencing photosynthesis).[10]

Parent material, the underlying geological material that gives rise to soils, determines the nature of the soils present, and influences the supply of mineral nutrients. Topography also controls ecosystem processes by affecting things like microclimate, soil development and the movement of water through a system. This may be the difference between the ecosystem present in wetland situated in a small depression on the landscape, and one present on an adjacent steep hillside.[10]

Other external factors that play an important role in ecosystem functioning include time and potential biota. Similarly, the set of organisms that can potentially be present in an area can also have a major impact on ecosystems. Ecosystems in similar environments that are located in different parts of the world can end up doing things very differently simply because they have different pools of species present.[10] The introduction of non-native species can cause substantial shifts in ecosystem function.

Unlike external factors, internal factors in ecosystems not only control ecosystem processes, but are also controlled by them. Consequently, they are often subject to feedback loops.[10] While the resource inputs are generally controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading.[10] Other factors like disturbance, succession or the types of species present are also internal factors.

Primary production is the production of organic matter from inorganic carbon sources. This mainly occurs through photosynthesis. The energy incorporated through this process supports life on earth, while the carbon makes up much of the organic matter in living and dead biomass, soil carbon and fossil fuels. It also drives the carbon cycle, which influences global climate via the greenhouse effect.

Through the process of photosynthesis, plants capture energy from light and use it to combine carbon dioxide and water to produce carbohydrates and oxygen. The photosynthesis carried out by all the plants in an ecosystem is called the gross primary production (GPP).[18] About 4860% of the GPP is consumed in plant respiration.

The remainder, that portion of GPP that is not used up by respiration, is known as the net primary production (NPP).[19]

Energy and carbon enter ecosystems through photosynthesis, are incorporated into living tissue, transferred to other organisms that feed on the living and dead plant matter, and eventually released through respiration.[19]

The carbon and energy incorporated into plant tissues (net primary production) is either consumed by animals while the plant is alive, or it remains uneaten when the plant tissue dies and becomes detritus. In terrestrial ecosystems, roughly 90% of the net primary production ends up being broken down by decomposers. The remainder is either consumed by animals while still alive and enters the plant-based trophic system, or it is consumed after it has died, and enters the detritus-based trophic system.

In aquatic systems, the proportion of plant biomass that gets consumed by herbivores is much higher.[20] In trophic systems photosynthetic organisms are the primary producers. The organisms that consume their tissues are called primary consumers or secondary producersherbivores. Organisms which feed on microbes (bacteria and fungi) are termed microbivores. Animals that feed on primary consumerscarnivoresare secondary consumers. Each of these constitutes a trophic level.[20]

The sequence of consumptionfrom plant to herbivore, to carnivoreforms a food chain. Real systems are much more complex than thisorganisms will generally feed on more than one form of food, and may feed at more than one trophic level. Carnivores may capture some prey which are part of a plant-based trophic system and others that are part of a detritus-based trophic system (a bird that feeds both on herbivorous grasshoppers and earthworms, which consume detritus). Real systems, with all these complexities, form food webs rather than food chains.[20]

Ecosystem ecology studies “the flow of energy and materials through organisms and the physical environment”. It seeks to understand the processes which govern the stocks of material and energy in ecosystems, and the flow of matter and energy through them. The study of ecosystems can cover 10 orders of magnitude, from the surface layers of rocks to the surface of the planet.[21]

The carbon and nutrients in dead organic matter are broken down by a group of processes known as decomposition. This releases nutrients that can then be re-used for plant and microbial production, and returns carbon dioxide to the atmosphere (or water) where it can be used for photosynthesis. In the absence of decomposition, dead organic matter would accumulate in an ecosystem, and nutrients and atmospheric carbon dioxide would be depleted.[22] Approximately 90% of terrestrial net primary production goes directly from plant to decomposer.[20]

Decomposition processes can be separated into three categoriesleaching, fragmentation and chemical alteration of dead material.

As water moves through dead organic matter, it dissolves and carries with it the water-soluble components. These are then taken up by organisms in the soil, react with mineral soil, or are transported beyond the confines of the ecosystem (and are considered lost to it).[22] Newly shed leaves and newly dead animals have high concentrations of water-soluble components, and include sugars, amino acids and mineral nutrients. Leaching is more important in wet environments, and much less important in dry ones.[22]

Fragmentation processes break organic material into smaller pieces, exposing new surfaces for colonization by microbes. Freshly shed leaf litter may be inaccessible due to an outer layer of cuticle or bark, and cell contents are protected by a cell wall. Newly dead animals may be covered by an exoskeleton. Fragmentation processes, which break through these protective layers, accelerate the rate of microbial decomposition.[22] Animals fragment detritus as they hunt for food, as does passage through the gut. Freeze-thaw cycles and cycles of wetting and drying also fragment dead material.[22]

The chemical alteration of dead organic matter is primarily achieved through bacterial and fungal action. Fungal hyphae produce enzymes which can break through the tough outer structures surrounding dead plant material. They also produce enzymes which break down lignin, which allows them access to both cell contents and to the nitrogen in the lignin. Fungi can transfer carbon and nitrogen through their hyphal networks and thus, unlike bacteria, are not dependent solely on locally available resources.[22]

Decomposition rates vary among ecosystems. The rate of decomposition is governed by three sets of factorsthe physical environment (temperature, moisture and soil properties), the quantity and quality of the dead material available to decomposers, and the nature of the microbial community itself.[23] Temperature controls the rate of microbial respiration; the higher the temperature, the faster microbial decomposition occurs. It also affects soil moisture, which slows microbial growth and reduces leaching. Freeze-thaw cycles also affect decompositionfreezing temperatures kill soil microorganisms, which allows leaching to play a more important role in moving nutrients around. This can be especially important as the soil thaws in the spring, creating a pulse of nutrients which become available.[23]

Decomposition rates are low under very wet or very dry conditions. Decomposition rates are highest in wet, moist conditions with adequate levels of oxygen. Wet soils tend to become deficient in oxygen (this is especially true in wetlands), which slows microbial growth. In dry soils, decomposition slows as well, but bacteria continue to grow (albeit at a slower rate) even after soils become too dry to support plant growth.

Ecosystems continually exchange energy and carbon with the wider environment. Mineral nutrients, on the other hand, are mostly cycled back and forth between plants, animals, microbes and the soil. Most nitrogen enters ecosystems through biological nitrogen fixation, is deposited through precipitation, dust, gases or is applied as fertilizer.[24]

Since most terrestrial ecosystems are nitrogen-limited, nitrogen cycling is an important control on ecosystem production.[24]

Until modern times, nitrogen fixation was the major source of nitrogen for ecosystems. Nitrogen fixing bacteria either live symbiotically with plants, or live freely in the soil. The energetic cost is high for plants which support nitrogen-fixing symbiontsas much as 25% of gross primary production when measured in controlled conditions. Many members of the legume plant family support nitrogen-fixing symbionts. Some cyanobacteria are also capable of nitrogen fixation. These are phototrophs, which carry out photosynthesis. Like other nitrogen-fixing bacteria, they can either be free-living or have symbiotic relationships with plants.[24] Other sources of nitrogen include acid deposition produced through the combustion of fossil fuels, ammonia gas which evaporates from agricultural fields which have had fertilizers applied to them, and dust.[24] Anthropogenic nitrogen inputs account for about 80% of all nitrogen fluxes in ecosystems.[24]

When plant tissues are shed or are eaten, the nitrogen in those tissues becomes available to animals and microbes. Microbial decomposition releases nitrogen compounds from dead organic matter in the soil, where plants, fungi and bacteria compete for it. Some soil bacteria use organic nitrogen-containing compounds as a source of carbon, and release ammonium ions into the soil. This process is known as nitrogen mineralization. Others convert ammonium to nitrite and nitrate ions, a process known as nitrification. Nitric oxide and nitrous oxide are also produced during nitrification.[24] Under nitrogen-rich and oxygen-poor conditions, nitrates and nitrites are converted to nitrogen gas, a process known as denitrification.[24]

Other important nutrients include phosphorus, sulfur, calcium, potassium, magnesium and manganese.[25] Phosphorus enters ecosystems through weathering. As ecosystems age this supply diminishes, making phosphorus-limitation more common in older landscapes (especially in the tropics).[25] Calcium and sulfur are also produced by weathering, but acid deposition is an important source of sulfur in many ecosystems. Although magnesium and manganese are produced by weathering, exchanges between soil organic matter and living cells account for a significant portion of ecosystem fluxes. Potassium is primarily cycled between living cells and soil organic matter.[25]

Biodiversity plays an important role in ecosystem functioning.[27] The reason for this is that ecosystem processes are driven by the number of species in an ecosystem, the exact nature of each individual species, and the relative abundance organisms within these species.[28] Ecosystem processes are broad generalizations that actually take place through the actions of individual organisms. The nature of the organismsthe species, functional groups and trophic levels to which they belongdictates the sorts of actions these individuals are capable of carrying out, and the relative efficiency with which they do so.

Ecological theory suggests that in order to coexist, species must have some level of limiting similaritythey must be different from one another in some fundamental way, otherwise one species would competitively exclude the other.[29] Despite this, the cumulative effect of additional species in an ecosystem is not linearadditional species may enhance nitrogen retention, for example, but beyond some level of species richness, additional species may have little additive effect.[28]

The addition (or loss) of species which are ecologically similar to those already present in an ecosystem tends to only have a small effect on ecosystem function. Ecologically distinct species, on the other hand, have a much larger effect. Similarly, dominant species have a large impact on ecosystem function, while rare species tend to have a small effect. Keystone species tend to have an effect on ecosystem function that is disproportionate to their abundance in an ecosystem.[28] Similarly, an ecosystem engineer is any organism that creates, significantly modifies, maintains or destroys a habitat.

Ecosystems are dynamic entities. They are subject to periodic disturbances and are in the process of recovering from some past disturbance.[11] When a perturbation occurs, an ecoystem responds by moving away from its initial state. The tendency of an ecosystem to remain close to its equilibrium state, despite that disturbance, is termed its resistance. On the other hand, the speed with which it returns to its initial state after disturbance is called its resilience.[11] Time plays a role in the development of soil from bare rock and the recovery of a community from disturbance.[10]

From one year to another, ecosystems experience variation in their biotic and abiotic environments. A drought, an especially cold winter and a pest outbreak all constitute short-term variability in environmental conditions. Animal populations vary from year to year, building up during resource-rich periods and crashing as they overshoot their food supply. These changes play out in changes in net primary production decomposition rates, and other ecosystem processes.[11] Longer-term changes also shape ecosystem processesthe forests of eastern North America still show legacies of cultivation which ceased 200 years ago, while methane production in eastern Siberian lakes is controlled by organic matter which accumulated during the Pleistocene.[11]

Disturbance also plays an important role in ecological processes. F. Stuart Chapin and coauthors define disturbance as “a relatively discrete event in time and space that alters the structure of populations, communities and ecosystems and causes changes in resources availability or the physical environment”.[30] This can range from tree falls and insect outbreaks to hurricanes and wildfires to volcanic eruptions. Such disturbances can cause large changes in plant, animal and microbe populations, as well soil organic matter content.[11] Disturbance is followed by succession, a “directional change in ecosystem structure and functioning resulting from biotically driven changes in resources supply.”[30]

The frequency and severity of disturbance determines the way it impacts ecosystem function. Major disturbance like a volcanic eruption or glacial advance and retreat leave behind soils that lack plants, animals or organic matter. Ecosystems that experience such disturbances undergo primary succession. Less severe disturbance like forest fires, hurricanes or cultivation result in secondary succession and a faster recovery.[11] More severe disturbance and more frequent disturbance result in longer recovery times.

Classifying ecosystems into ecologically homogeneous units is an important step towards effective ecosystem management.[31] There is no single, agreed-upon way to do this. A variety of systems exist, based on vegetation cover, remote sensing, and bioclimatic classification systems.[31]

Ecological land classification is a cartographical delineation or regionalisation of distinct ecological areas, identified by their geology, topography, soils, vegetation, climate conditions, living species, habitats, water resources, and sometimes also anthropic factors.[32]

Human activities are important in almost all ecosystems. Although humans exist and operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.[10]

Ecosystems provide a variety of goods and services upon which people depend.[33] Ecosystem goods include the “tangible, material products” of ecosystem processes such as food, construction material, medicinal plants.[34] They also include less tangible items like tourism and recreation, and genes from wild plants and animals that can be used to improve domestic species.[33]

Ecosystem services, on the other hand, are generally “improvements in the condition or location of things of value”.[34] These include things like the maintenance of hydrological cycles, cleaning air and water, the maintenance of oxygen in the atmosphere, crop pollination and even things like beauty, inspiration and opportunities for research.[33] While ecosystem goods have traditionally been recognized as being the basis for things of economic value, ecosystem services tend to be taken for granted.[34]

When natural resource management is applied to whole ecosystems, rather than single species, it is termed ecosystem management.[35] Although definitions of ecosystem management abound, there is a common set of principles which underlie these definitions.[36] A fundamental principle is the long-term sustainability of the production of goods and services by the ecosystem;[36] “intergenerational sustainability [is] a precondition for management, not an afterthought”.[33]

While ecosystem management can be used as part of a plan for wilderness conservation, it can also be used in intensively managed ecosystems[33] (see, for example, agroecosystem and close to nature forestry).

As human populations and per capita consumption grow, so do the resource demands imposed on ecosystems and the impacts of the human ecological footprint. Natural resources are vulnerable and limited. The environmental impacts of anthropogenic actions are becoming more apparent. Problems for all ecosystems include: environmental pollution, climate change and biodiversity loss. For terrestrial ecosystems further threats include air pollution, soil degradation, and deforestation. For aquatic ecosystems threats include also unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollution, microplastics pollution, water pollution, and building on coastal areas.[37]

Society is increasingly becoming aware that ecosystem services are not only limited, but also that they are threatened by human activities. The need to better consider long-term ecosystem health and its role in enabling human habitation and economic activity is urgent. To help inform decision-makers, many ecosystem services are being assigned economic values, often based on the cost of replacement with anthropogenic alternatives. The ongoing challenge of prescribing economic value to nature, for example through biodiversity banking, is prompting transdisciplinary shifts in how we recognize and manage the environment, social responsibility, business opportunities, and our future as a species.[citation needed]

The term “ecosystem” was first used in 1935 in a publication by British ecologist Arthur Tansley.[fn 1][38] Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment.[39] He later refined the term, describing it as “The whole system, … including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment”.[40] Tansley regarded ecosystems not simply as natural units, but as “mental isolates”.[40] Tansley later defined the spatial extent of ecosystems using the term ecotope.[41]

G. Evelyn Hutchinson, a limnologist who was a contemporary of Tansley’s, combined Charles Elton’s ideas about trophic ecology with those of Russian geochemist Vladimir Vernadsky. As a result he suggested that mineral nutrient availability in a lake limited algal production. This would, in turn, limit the abundance of animals that feed on algae. Raymond Lindeman took these ideas further to suggest that the flow of energy through a lake was the primary driver of the ecosystem. Hutchinson’s students, brothers Howard T. Odum and Eugene P. Odum, further developed a “systems approach” to the study of ecosystems. This allowed them to study the flow of energy and material through ecological systems.[39]

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Ecosystem – Wikipedia

FintruX – The Global P2P Lending Ecosystem

Chairman of the Board Yew Poh Leong

YP grew Dun & Bradstreet Software from 15 to over 250 employees as a managing director in Asia. He has provided business solutions and services to well-known corporations including Telekom Malaysia, Hong Kong Telecom, PLDT, Communications Authority of Thailand, Shell, Prudential, AIG, Starwood, Minolta, National Panasonic, Sony, Aiwa, Standard Chartered Bank, Malayan Banking, Bank of China, etc.

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Ecosystem – Wikipedia

This article is about natural ecosystems. For the term used in man-made systems, see Digital ecosystem.

An ecosystem is a community made up of living organisms and nonliving components such as air, water and mineral soil.[3] Ecosystems may be studied either as contingent collections of plants and animals, or as structured systems and communities that are governed by general rules.[4] The biotic and abiotic components interact through nutrient cycles and energy flows.[5] Ecosystems include a network of interactions among organisms, and between organisms and their environment.[6] Ecosystems can be of any size but one ecosystem has a specific, limited space.[7] Some scientists view the entire planet as one ecosystem.[8]

Energy, water, nitrogen and soil minerals are other essential abiotic components of an ecosystem. The energy that flows through ecosystems comes primarily from the sun, through photosynthesis. Photosynthesis also captures carbon dioxide from the atmosphere. Animals also play an important role in the movement of matter and energy through ecoystems. They influence the amount of plant and microbial biomass that lives in the system. As organic matter dies, decomposers release carbon back to the atmosphere. This process also facilitates nutrient cycling by converting nutrients stored in dead biomass back to a form that can be used again by plants and other microbes.[9]

Ecosystems are controlled both by external and internal factors. External factors such as climate, the parent material that forms the soil, topography and time have a big impact on ecosystems, but they are not themselves influenced by the ecosystem.[10] Ecosystems are dynamic: they are subject to periodic disturbances and are in the process of recovering from past disturbances.[11] Internal factors are different: They not only control ecosystem processes but are also controlled by them. Internal factors are subject to feedback loops.[10]

Humans operate within ecosystems. The effects of human activities can influence internal and external factors.[10] Global warming is an example of a cumulative impact of human activities. Ecosystems provide benefits, called “ecosystem services”, which people depend on for their livelihood. Ecosystem management is more efficient than trying to manage individual species.

There is no single definition of what constitutes an ecosystem.[4] German ecologist Ernst-Detlef Schulze and coauthors defined an ecosystem as an area which is “uniform regarding the biological turnover, and contains all the fluxes above and below the ground area under consideration.” They explicitly reject Gene Likens’ use of entire river catchments as “too wide a demarcation” to be a single ecosystem, given the level of heterogeneity within such an area.[12] Other authors have suggested that an ecosystem can encompass a much larger area, even the whole planet.[8] Schulze and coauthors also rejected the idea that a single rotting log could be studied as an ecosystem because the size of the flows between the log and its surroundings are too large, relative to the proportion cycles within the log.[12] Philosopher of science Mark Sagoff considers the failure to define “the kind of object it studies” to be an obstacle to the development of theory in ecosystem ecology.[4]

Ecosystems can be studied through a variety of approachestheoretical studies, studies monitoring specific ecosystems over long periods of time, those that look at differences between ecosystems to elucidate how they work and direct manipulative experimentation.[13] Studies can be carried out at a variety of scales, from microcosms and mesocosms which serve as simplified representations of ecosystems, through whole-ecosystem studies.[14] American ecologist Stephen R. Carpenter has argued that microcosm experiments can be “irrelevant and diversionary” if they are not carried out in conjunction with field studies carried out at the ecosystem scale, because microcosm experiments often fail to accurately predict ecosystem-level dynamics.[15]

The Hubbard Brook Ecosystem Study, established in the White Mountains, New Hampshire in 1963, was the first successful attempt to study an entire watershed as an ecosystem. The study used stream chemistry as a means of monitoring ecosystem properties, and developed a detailed biogeochemical model of the ecosystem.[16] Long-term research at the site led to the discovery of acid rain in North America in 1972, and was able to document the consequent depletion of soil cations (especially calcium) over the next several decades.[17]

The term “ecosystem” is often used very imprecisely and linked with a descriptive term (adjective) even if those systems are rather biomes, not ecosystems.[citation needed] Examples include: terrestrial ecosystem or aquatic ecosystems. Aquatic ecosystems are split into marine ecosystems (Large marine ecosystem is another term used) and freshwater ecosystems.

Ecosystems are controlled both by external and internal factors. External factors, also called state factors, control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem. The most important of these is climate.[10] Climate determines the biome in which the ecosystem is embedded. Rainfall patterns and temperature seasonality determine the amount of water available to the ecosystem and the supply of energy available (by influencing photosynthesis).[10]

Parent material, the underlying geological material that gives rise to soils, determines the nature of the soils present, and influences the supply of mineral nutrients. Topography also controls ecosystem processes by affecting things like microclimate, soil development and the movement of water through a system. This may be the difference between the ecosystem present in wetland situated in a small depression on the landscape, and one present on an adjacent steep hillside.[10]

Other external factors that play an important role in ecosystem functioning include time and potential biota. Similarly, the set of organisms that can potentially be present in an area can also have a major impact on ecosystems. Ecosystems in similar environments that are located in different parts of the world can end up doing things very differently simply because they have different pools of species present.[10] The introduction of non-native species can cause substantial shifts in ecosystem function.

Unlike external factors, internal factors in ecosystems not only control ecosystem processes, but are also controlled by them. Consequently, they are often subject to feedback loops.[10] While the resource inputs are generally controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading.[10] Other factors like disturbance, succession or the types of species present are also internal factors.

Primary production is the production of organic matter from inorganic carbon sources. This mainly occurs through photosynthesis. The energy incorporated through this process supports life on earth, while the carbon makes up much of the organic matter in living and dead biomass, soil carbon and fossil fuels. It also drives the carbon cycle, which influences global climate via the greenhouse effect.

Through the process of photosynthesis, plants capture energy from light and use it to combine carbon dioxide and water to produce carbohydrates and oxygen. The photosynthesis carried out by all the plants in an ecosystem is called the gross primary production (GPP).[18] About 4860% of the GPP is consumed in plant respiration.

The remainder, that portion of GPP that is not used up by respiration, is known as the net primary production (NPP).[19]

Energy and carbon enter ecosystems through photosynthesis, are incorporated into living tissue, transferred to other organisms that feed on the living and dead plant matter, and eventually released through respiration.[19]

The carbon and energy incorporated into plant tissues (net primary production) is either consumed by animals while the plant is alive, or it remains uneaten when the plant tissue dies and becomes detritus. In terrestrial ecosystems, roughly 90% of the net primary production ends up being broken down by decomposers. The remainder is either consumed by animals while still alive and enters the plant-based trophic system, or it is consumed after it has died, and enters the detritus-based trophic system.

In aquatic systems, the proportion of plant biomass that gets consumed by herbivores is much higher.[20] In trophic systems photosynthetic organisms are the primary producers. The organisms that consume their tissues are called primary consumers or secondary producersherbivores. Organisms which feed on microbes (bacteria and fungi) are termed microbivores. Animals that feed on primary consumerscarnivoresare secondary consumers. Each of these constitutes a trophic level.[20]

The sequence of consumptionfrom plant to herbivore, to carnivoreforms a food chain. Real systems are much more complex than thisorganisms will generally feed on more than one form of food, and may feed at more than one trophic level. Carnivores may capture some prey which are part of a plant-based trophic system and others that are part of a detritus-based trophic system (a bird that feeds both on herbivorous grasshoppers and earthworms, which consume detritus). Real systems, with all these complexities, form food webs rather than food chains.[20]

Ecosystem ecology studies “the flow of energy and materials through organisms and the physical environment”. It seeks to understand the processes which govern the stocks of material and energy in ecosystems, and the flow of matter and energy through them. The study of ecosystems can cover 10 orders of magnitude, from the surface layers of rocks to the surface of the planet.[21]

The carbon and nutrients in dead organic matter are broken down by a group of processes known as decomposition. This releases nutrients that can then be re-used for plant and microbial production, and returns carbon dioxide to the atmosphere (or water) where it can be used for photosynthesis. In the absence of decomposition, dead organic matter would accumulate in an ecosystem, and nutrients and atmospheric carbon dioxide would be depleted.[22] Approximately 90% of terrestrial net primary production goes directly from plant to decomposer.[20]

Decomposition processes can be separated into three categoriesleaching, fragmentation and chemical alteration of dead material.

As water moves through dead organic matter, it dissolves and carries with it the water-soluble components. These are then taken up by organisms in the soil, react with mineral soil, or are transported beyond the confines of the ecosystem (and are considered lost to it).[22] Newly shed leaves and newly dead animals have high concentrations of water-soluble components, and include sugars, amino acids and mineral nutrients. Leaching is more important in wet environments, and much less important in dry ones.[22]

Fragmentation processes break organic material into smaller pieces, exposing new surfaces for colonization by microbes. Freshly shed leaf litter may be inaccessible due to an outer layer of cuticle or bark, and cell contents are protected by a cell wall. Newly dead animals may be covered by an exoskeleton. Fragmentation processes, which break through these protective layers, accelerate the rate of microbial decomposition.[22] Animals fragment detritus as they hunt for food, as does passage through the gut. Freeze-thaw cycles and cycles of wetting and drying also fragment dead material.[22]

The chemical alteration of dead organic matter is primarily achieved through bacterial and fungal action. Fungal hyphae produce enzymes which can break through the tough outer structures surrounding dead plant material. They also produce enzymes which break down lignin, which allows them access to both cell contents and to the nitrogen in the lignin. Fungi can transfer carbon and nitrogen through their hyphal networks and thus, unlike bacteria, are not dependent solely on locally available resources.[22]

Decomposition rates vary among ecosystems. The rate of decomposition is governed by three sets of factorsthe physical environment (temperature, moisture and soil properties), the quantity and quality of the dead material available to decomposers, and the nature of the microbial community itself.[23] Temperature controls the rate of microbial respiration; the higher the temperature, the faster microbial decomposition occurs. It also affects soil moisture, which slows microbial growth and reduces leaching. Freeze-thaw cycles also affect decompositionfreezing temperatures kill soil microorganisms, which allows leaching to play a more important role in moving nutrients around. This can be especially important as the soil thaws in the spring, creating a pulse of nutrients which become available.[23]

Decomposition rates are low under very wet or very dry conditions. Decomposition rates are highest in wet, moist conditions with adequate levels of oxygen. Wet soils tend to become deficient in oxygen (this is especially true in wetlands), which slows microbial growth. In dry soils, decomposition slows as well, but bacteria continue to grow (albeit at a slower rate) even after soils become too dry to support plant growth.

Ecosystems continually exchange energy and carbon with the wider environment. Mineral nutrients, on the other hand, are mostly cycled back and forth between plants, animals, microbes and the soil. Most nitrogen enters ecosystems through biological nitrogen fixation, is deposited through precipitation, dust, gases or is applied as fertilizer.[24]

Since most terrestrial ecosystems are nitrogen-limited, nitrogen cycling is an important control on ecosystem production.[24]

Until modern times, nitrogen fixation was the major source of nitrogen for ecosystems. Nitrogen fixing bacteria either live symbiotically with plants, or live freely in the soil. The energetic cost is high for plants which support nitrogen-fixing symbiontsas much as 25% of gross primary production when measured in controlled conditions. Many members of the legume plant family support nitrogen-fixing symbionts. Some cyanobacteria are also capable of nitrogen fixation. These are phototrophs, which carry out photosynthesis. Like other nitrogen-fixing bacteria, they can either be free-living or have symbiotic relationships with plants.[24] Other sources of nitrogen include acid deposition produced through the combustion of fossil fuels, ammonia gas which evaporates from agricultural fields which have had fertilizers applied to them, and dust.[24] Anthropogenic nitrogen inputs account for about 80% of all nitrogen fluxes in ecosystems.[24]

When plant tissues are shed or are eaten, the nitrogen in those tissues becomes available to animals and microbes. Microbial decomposition releases nitrogen compounds from dead organic matter in the soil, where plants, fungi and bacteria compete for it. Some soil bacteria use organic nitrogen-containing compounds as a source of carbon, and release ammonium ions into the soil. This process is known as nitrogen mineralization. Others convert ammonium to nitrite and nitrate ions, a process known as nitrification. Nitric oxide and nitrous oxide are also produced during nitrification.[24] Under nitrogen-rich and oxygen-poor conditions, nitrates and nitrites are converted to nitrogen gas, a process known as denitrification.[24]

Other important nutrients include phosphorus, sulfur, calcium, potassium, magnesium and manganese.[25] Phosphorus enters ecosystems through weathering. As ecosystems age this supply diminishes, making phosphorus-limitation more common in older landscapes (especially in the tropics).[25] Calcium and sulfur are also produced by weathering, but acid deposition is an important source of sulfur in many ecosystems. Although magnesium and manganese are produced by weathering, exchanges between soil organic matter and living cells account for a significant portion of ecosystem fluxes. Potassium is primarily cycled between living cells and soil organic matter.[25]

Biodiversity plays an important role in ecosystem functioning.[27] The reason for this is that ecosystem processes are driven by the number of species in an ecosystem, the exact nature of each individual species, and the relative abundance organisms within these species.[28] Ecosystem processes are broad generalizations that actually take place through the actions of individual organisms. The nature of the organismsthe species, functional groups and trophic levels to which they belongdictates the sorts of actions these individuals are capable of carrying out, and the relative efficiency with which they do so.

Ecological theory suggests that in order to coexist, species must have some level of limiting similaritythey must be different from one another in some fundamental way, otherwise one species would competitively exclude the other.[29] Despite this, the cumulative effect of additional species in an ecosystem is not linearadditional species may enhance nitrogen retention, for example, but beyond some level of species richness, additional species may have little additive effect.[28]

The addition (or loss) of species which are ecologically similar to those already present in an ecosystem tends to only have a small effect on ecosystem function. Ecologically distinct species, on the other hand, have a much larger effect. Similarly, dominant species have a large impact on ecosystem function, while rare species tend to have a small effect. Keystone species tend to have an effect on ecosystem function that is disproportionate to their abundance in an ecosystem.[28] Similarly, an ecosystem engineer is any organism that creates, significantly modifies, maintains or destroys a habitat.

Ecosystems are dynamic entities. They are subject to periodic disturbances and are in the process of recovering from some past disturbance.[11] When a perturbation occurs, an ecoystem responds by moving away from its initial state. The tendency of an ecosystem to remain close to its equilibrium state, despite that disturbance, is termed its resistance. On the other hand, the speed with which it returns to its initial state after disturbance is called its resilience.[11] Time plays a role in the development of soil from bare rock and the recovery of a community from disturbance.[10]

From one year to another, ecosystems experience variation in their biotic and abiotic environments. A drought, an especially cold winter and a pest outbreak all constitute short-term variability in environmental conditions. Animal populations vary from year to year, building up during resource-rich periods and crashing as they overshoot their food supply. These changes play out in changes in net primary production decomposition rates, and other ecosystem processes.[11] Longer-term changes also shape ecosystem processesthe forests of eastern North America still show legacies of cultivation which ceased 200 years ago, while methane production in eastern Siberian lakes is controlled by organic matter which accumulated during the Pleistocene.[11]

Disturbance also plays an important role in ecological processes. F. Stuart Chapin and coauthors define disturbance as “a relatively discrete event in time and space that alters the structure of populations, communities and ecosystems and causes changes in resources availability or the physical environment”.[30] This can range from tree falls and insect outbreaks to hurricanes and wildfires to volcanic eruptions. Such disturbances can cause large changes in plant, animal and microbe populations, as well soil organic matter content.[11] Disturbance is followed by succession, a “directional change in ecosystem structure and functioning resulting from biotically driven changes in resources supply.”[30]

The frequency and severity of disturbance determines the way it impacts ecosystem function. Major disturbance like a volcanic eruption or glacial advance and retreat leave behind soils that lack plants, animals or organic matter. Ecosystems that experience such disturbances undergo primary succession. Less severe disturbance like forest fires, hurricanes or cultivation result in secondary succession and a faster recovery.[11] More severe disturbance and more frequent disturbance result in longer recovery times.

Classifying ecosystems into ecologically homogeneous units is an important step towards effective ecosystem management.[31] There is no single, agreed-upon way to do this. A variety of systems exist, based on vegetation cover, remote sensing, and bioclimatic classification systems.[31]

Ecological land classification is a cartographical delineation or regionalisation of distinct ecological areas, identified by their geology, topography, soils, vegetation, climate conditions, living species, habitats, water resources, and sometimes also anthropic factors.[32]

Human activities are important in almost all ecosystems. Although humans exist and operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.[10]

Ecosystems provide a variety of goods and services upon which people depend.[33] Ecosystem goods include the “tangible, material products” of ecosystem processes such as food, construction material, medicinal plants.[34] They also include less tangible items like tourism and recreation, and genes from wild plants and animals that can be used to improve domestic species.[33]

Ecosystem services, on the other hand, are generally “improvements in the condition or location of things of value”.[34] These include things like the maintenance of hydrological cycles, cleaning air and water, the maintenance of oxygen in the atmosphere, crop pollination and even things like beauty, inspiration and opportunities for research.[33] While ecosystem goods have traditionally been recognized as being the basis for things of economic value, ecosystem services tend to be taken for granted.[34]

When natural resource management is applied to whole ecosystems, rather than single species, it is termed ecosystem management.[35] Although definitions of ecosystem management abound, there is a common set of principles which underlie these definitions.[36] A fundamental principle is the long-term sustainability of the production of goods and services by the ecosystem;[36] “intergenerational sustainability [is] a precondition for management, not an afterthought”.[33]

While ecosystem management can be used as part of a plan for wilderness conservation, it can also be used in intensively managed ecosystems[33] (see, for example, agroecosystem and close to nature forestry).

As human populations and per capita consumption grow, so do the resource demands imposed on ecosystems and the impacts of the human ecological footprint. Natural resources are vulnerable and limited. The environmental impacts of anthropogenic actions are becoming more apparent. Problems for all ecosystems include: environmental pollution, climate change and biodiversity loss. For terrestrial ecosystems further threats include air pollution, soil degradation, and deforestation. For aquatic ecosystems threats include also unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollution, microplastics pollution, water pollution, and building on coastal areas.[37]

Society is increasingly becoming aware that ecosystem services are not only limited, but also that they are threatened by human activities. The need to better consider long-term ecosystem health and its role in enabling human habitation and economic activity is urgent. To help inform decision-makers, many ecosystem services are being assigned economic values, often based on the cost of replacement with anthropogenic alternatives. The ongoing challenge of prescribing economic value to nature, for example through biodiversity banking, is prompting transdisciplinary shifts in how we recognize and manage the environment, social responsibility, business opportunities, and our future as a species.[citation needed]

The term “ecosystem” was first used in 1935 in a publication by British ecologist Arthur Tansley.[fn 1][38] Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment.[39] He later refined the term, describing it as “The whole system, … including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment”.[40] Tansley regarded ecosystems not simply as natural units, but as “mental isolates”.[40] Tansley later defined the spatial extent of ecosystems using the term ecotope.[41]

G. Evelyn Hutchinson, a limnologist who was a contemporary of Tansley’s, combined Charles Elton’s ideas about trophic ecology with those of Russian geochemist Vladimir Vernadsky. As a result he suggested that mineral nutrient availability in a lake limited algal production. This would, in turn, limit the abundance of animals that feed on algae. Raymond Lindeman took these ideas further to suggest that the flow of energy through a lake was the primary driver of the ecosystem. Hutchinson’s students, brothers Howard T. Odum and Eugene P. Odum, further developed a “systems approach” to the study of ecosystems. This allowed them to study the flow of energy and material through ecological systems.[39]

See the original post here:

Ecosystem – Wikipedia

FintruX – The Global P2P Lending Ecosystem

Chairman of the Board Yew Poh Leong

YP grew Dun & Bradstreet Software from 15 to over 250 employees as a managing director in Asia. He has provided business solutions and services to well-known corporations including Telekom Malaysia, Hong Kong Telecom, PLDT, Communications Authority of Thailand, Shell, Prudential, AIG, Starwood, Minolta, National Panasonic, Sony, Aiwa, Standard Chartered Bank, Malayan Banking, Bank of China, etc.

Read more from the original source:

FintruX – The Global P2P Lending Ecosystem

Ecosystem – Wikipedia

This article is about natural ecosystems. For the term used in man-made systems, see Digital ecosystem.

An ecosystem is a community made up of living organisms and nonliving components such as air, water and mineral soil.[2] Ecosystems may be studied either as contingent collections of plants and animals, or as structured systems and communities that are governed by general rules.[3] The biotic and abiotic components interact through nutrient cycles and energy flows.[4] Ecosystems include a network of interactions among organisms, and between organisms and their environment.[5] Ecosystems can be of any size but one ecosystem has a specific, limited space.[6] Some scientists view the entire planet as one ecosystem.[7]

Energy, water, nitrogen and soil minerals are other essential abiotic components of an ecosystem. The energy that flows through ecosystems comes primarily from the sun, through photosynthesis. Photosynthesis also captures carbon dioxide from the atmosphere. Animals also play an important role in the movement of matter and energy through ecoystems. They influence the amount of plant and microbial biomass that lives in the system. As organic matter dies, decomposers release carbon back to the atmosphere. This process also facilitates nutrient cycling by converting nutrients stored in dead biomass back to a form that can be used again by plants and other microbes.[8]

Ecosystems are controlled both by external and internal factors. External factors such as climate, the parent material that forms the soil, topography and time have a big impact on ecosystems, but they are not themselves influenced by the ecosystem.[9] Ecosystems are dynamic: they are subject to periodic disturbances and are in the process of recovering from past disturbances.[10] Internal factors are different: They not only control ecosystem processes but are also controlled by them. Internal factors are subject to feedback loops.[9]

Humans operate within ecosystems. The effects of human activities can influence internal and external factors.[9] Global warming is an example of a cumulative impact of human activities. Ecosystems provide benefits, called “ecosystem services”, which people depend on for their livelihood. Ecosystem management is more efficient than trying to manage individual species.

There is no single definition of what constitutes an ecosystem.[3] German ecologist Ernst-Detlef Schulze and coauthors defined an ecosystem as an area which is “uniform regarding the biological turnover, and contains all the fluxes above and below the ground area under consideration.” They explicitly reject Gene Likens’ use of entire river catchments as “too wide a demarcation” to be a single ecosystem, given the level of heterogeneity within such an area.[11] Other authors have suggested that an ecosystem can encompass a much larger area, even the whole planet.[7] Schulze and coauthors also rejected the idea that a single rotting log could be studied as an ecosystem because the size of the flows between the log and its surroundings are too large, relative to the proportion cycles within the log.[11] Philosopher of science Mark Sagoff considers the failure to define “the kind of object it studies” to be an obstacle to the development of theory in ecosystem ecology.[3]

Ecosystems can be studied through a variety of approachestheoretical studies, studies monitoring specific ecosystems over long periods of time, those that look at differences between ecosystems to elucidate how they work and direct manipulative experimentation.[12] Studies can be carried out at a variety of scales, from microcosms and mesocosms which serve as simplified representations of ecosystems, through whole-ecosystem studies.[13] American ecologist Stephen R. Carpenter has argued that microcosm experiments can be “irrelevant and diversionary” if they are not carried out in conjunction with field studies carried out at the ecosystem scale, because microcosm experiments often fail to accurately predict ecosystem-level dynamics.[14]

The Hubbard Brook Ecosystem Study, established in the White Mountains, New Hampshire in 1963, was the first successful attempt to study an entire watershed as an ecosystem. The study used stream chemistry as a means of monitoring ecosystem properties, and developed a detailed biogeochemical model of the ecosystem.[15] Long-term research at the site led to the discovery of acid rain in North America in 1972, and was able to document the consequent depletion of soil cations (especially calcium) over the next several decades.[16]

The term “ecosystem” is often used very imprecisely and linked with a descriptive term (adjective) even if those systems are rather biomes, not ecosystems.[citation needed] Examples include: terrestrial ecosystem or aquatic ecosystems. Aquatic ecosystems are split into marine ecosystems (Large marine ecosystem is another term used) and freshwater ecosystems.

Ecosystems are controlled both by external and internal factors. External factors, also called state factors, control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem. The most important of these is climate.[9] Climate determines the biome in which the ecosystem is embedded. Rainfall patterns and temperature seasonality determine the amount of water available to the ecosystem and the supply of energy available (by influencing photosynthesis).[9]

Parent material, the underlying geological material that gives rise to soils, determines the nature of the soils present, and influences the supply of mineral nutrients. Topography also controls ecosystem processes by affecting things like microclimate, soil development and the movement of water through a system. This may be the difference between the ecosystem present in wetland situated in a small depression on the landscape, and one present on an adjacent steep hillside.[9]

Other external factors that play an important role in ecosystem functioning include time and potential biota. Similarly, the set of organisms that can potentially be present in an area can also have a major impact on ecosystems. Ecosystems in similar environments that are located in different parts of the world can end up doing things very differently simply because they have different pools of species present.[9] The introduction of non-native species can cause substantial shifts in ecosystem function.

Unlike external factors, internal factors in ecosystems not only control ecosystem processes, but are also controlled by them. Consequently, they are often subject to feedback loops.[9] While the resource inputs are generally controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading.[9] Other factors like disturbance, succession or the types of species present are also internal factors.

Primary production is the production of organic matter from inorganic carbon sources. This mainly occurs through photosynthesis. The energy incorporated through this process supports life on earth, while the carbon makes up much of the organic matter in living and dead biomass, soil carbon and fossil fuels. It also drives the carbon cycle, which influences global climate via the greenhouse effect.

Through the process of photosynthesis, plants capture energy from light and use it to combine carbon dioxide and water to produce carbohydrates and oxygen. The photosynthesis carried out by all the plants in an ecosystem is called the gross primary production (GPP).[17] About 4860% of the GPP is consumed in plant respiration.

The remainder, that portion of GPP that is not used up by respiration, is known as the net primary production (NPP).[18]

Energy and carbon enter ecosystems through photosynthesis, are incorporated into living tissue, transferred to other organisms that feed on the living and dead plant matter, and eventually released through respiration.[18]

The carbon and energy incorporated into plant tissues (net primary production) is either consumed by animals while the plant is alive, or it remains uneaten when the plant tissue dies and becomes detritus. In terrestrial ecosystems, roughly 90% of the net primary production ends up being broken down by decomposers. The remainder is either consumed by animals while still alive and enters the plant-based trophic system, or it is consumed after it has died, and enters the detritus-based trophic system.

In aquatic systems, the proportion of plant biomass that gets consumed by herbivores is much higher.[19] In trophic systems photosynthetic organisms are the primary producers. The organisms that consume their tissues are called primary consumers or secondary producersherbivores. Organisms which feed on microbes (bacteria and fungi) are termed microbivores. Animals that feed on primary consumerscarnivoresare secondary consumers. Each of these constitutes a trophic level.[19]

The sequence of consumptionfrom plant to herbivore, to carnivoreforms a food chain. Real systems are much more complex than thisorganisms will generally feed on more than one form of food, and may feed at more than one trophic level. Carnivores may capture some prey which are part of a plant-based trophic system and others that are part of a detritus-based trophic system (a bird that feeds both on herbivorous grasshoppers and earthworms, which consume detritus). Real systems, with all these complexities, form food webs rather than food chains.[19]

Ecosystem ecology studies “the flow of energy and materials through organisms and the physical environment”. It seeks to understand the processes which govern the stocks of material and energy in ecosystems, and the flow of matter and energy through them. The study of ecosystems can cover 10 orders of magnitude, from the surface layers of rocks to the surface of the planet.[20]

The carbon and nutrients in dead organic matter are broken down by a group of processes known as decomposition. This releases nutrients that can then be re-used for plant and microbial production, and returns carbon dioxide to the atmosphere (or water) where it can be used for photosynthesis. In the absence of decomposition, dead organic matter would accumulate in an ecosystem, and nutrients and atmospheric carbon dioxide would be depleted.[21] Approximately 90% of terrestrial net primary production goes directly from plant to decomposer.[19]

Decomposition processes can be separated into three categoriesleaching, fragmentation and chemical alteration of dead material.

As water moves through dead organic matter, it dissolves and carries with it the water-soluble components. These are then taken up by organisms in the soil, react with mineral soil, or are transported beyond the confines of the ecosystem (and are considered lost to it).[21] Newly shed leaves and newly dead animals have high concentrations of water-soluble components, and include sugars, amino acids and mineral nutrients. Leaching is more important in wet environments, and much less important in dry ones.[21]

Fragmentation processes break organic material into smaller pieces, exposing new surfaces for colonization by microbes. Freshly shed leaf litter may be inaccessible due to an outer layer of cuticle or bark, and cell contents are protected by a cell wall. Newly dead animals may be covered by an exoskeleton. Fragmentation processes, which break through these protective layers, accelerate the rate of microbial decomposition.[21] Animals fragment detritus as they hunt for food, as does passage through the gut. Freeze-thaw cycles and cycles of wetting and drying also fragment dead material.[21]

The chemical alteration of dead organic matter is primarily achieved through bacterial and fungal action. Fungal hyphae produce enzymes which can break through the tough outer structures surrounding dead plant material. They also produce enzymes which break down lignin, which allows them access to both cell contents and to the nitrogen in the lignin. Fungi can transfer carbon and nitrogen through their hyphal networks and thus, unlike bacteria, are not dependent solely on locally available resources.[21]

Decomposition rates vary among ecosystems. The rate of decomposition is governed by three sets of factorsthe physical environment (temperature, moisture and soil properties), the quantity and quality of the dead material available to decomposers, and the nature of the microbial community itself.[22] Temperature controls the rate of microbial respiration; the higher the temperature, the faster microbial decomposition occurs. It also affects soil moisture, which slows microbial growth and reduces leaching. Freeze-thaw cycles also affect decompositionfreezing temperatures kill soil microorganisms, which allows leaching to play a more important role in moving nutrients around. This can be especially important as the soil thaws in the spring, creating a pulse of nutrients which become available.[22]

Decomposition rates are low under very wet or very dry conditions. Decomposition rates are highest in wet, moist conditions with adequate levels of oxygen. Wet soils tend to become deficient in oxygen (this is especially true in wetlands), which slows microbial growth. In dry soils, decomposition slows as well, but bacteria continue to grow (albeit at a slower rate) even after soils become too dry to support plant growth.

Ecosystems continually exchange energy and carbon with the wider environment. Mineral nutrients, on the other hand, are mostly cycled back and forth between plants, animals, microbes and the soil. Most nitrogen enters ecosystems through biological nitrogen fixation, is deposited through precipitation, dust, gases or is applied as fertilizer.[23]

Since most terrestrial ecosystems are nitrogen-limited, nitrogen cycling is an important control on ecosystem production.[23]

Until modern times, nitrogen fixation was the major source of nitrogen for ecosystems. Nitrogen fixing bacteria either live symbiotically with plants, or live freely in the soil. The energetic cost is high for plants which support nitrogen-fixing symbiontsas much as 25% of gross primary production when measured in controlled conditions. Many members of the legume plant family support nitrogen-fixing symbionts. Some cyanobacteria are also capable of nitrogen fixation. These are phototrophs, which carry out photosynthesis. Like other nitrogen-fixing bacteria, they can either be free-living or have symbiotic relationships with plants.[23] Other sources of nitrogen include acid deposition produced through the combustion of fossil fuels, ammonia gas which evaporates from agricultural fields which have had fertilizers applied to them, and dust.[23] Anthropogenic nitrogen inputs account for about 80% of all nitrogen fluxes in ecosystems.[23]

When plant tissues are shed or are eaten, the nitrogen in those tissues becomes available to animals and microbes. Microbial decomposition releases nitrogen compounds from dead organic matter in the soil, where plants, fungi and bacteria compete for it. Some soil bacteria use organic nitrogen-containing compounds as a source of carbon, and release ammonium ions into the soil. This process is known as nitrogen mineralization. Others convert ammonium to nitrite and nitrate ions, a process known as nitrification. Nitric oxide and nitrous oxide are also produced during nitrification.[23] Under nitrogen-rich and oxygen-poor conditions, nitrates and nitrites are converted to nitrogen gas, a process known as denitrification.[23]

Other important nutrients include phosphorus, sulfur, calcium, potassium, magnesium and manganese.[24] Phosphorus enters ecosystems through weathering. As ecosystems age this supply diminishes, making phosphorus-limitation more common in older landscapes (especially in the tropics).[24] Calcium and sulfur are also produced by weathering, but acid deposition is an important source of sulfur in many ecosystems. Although magnesium and manganese are produced by weathering, exchanges between soil organic matter and living cells account for a significant portion of ecosystem fluxes. Potassium is primarily cycled between living cells and soil organic matter.[24]

Biodiversity plays an important role in ecosystem functioning.[26] The reason for this is that ecosystem processes are driven by the number of species in an ecosystem, the exact nature of each individual species, and the relative abundance organisms within these species.[27] Ecosystem processes are broad generalizations that actually take place through the actions of individual organisms. The nature of the organismsthe species, functional groups and trophic levels to which they belongdictates the sorts of actions these individuals are capable of carrying out, and the relative efficiency with which they do so.

Ecological theory suggests that in order to coexist, species must have some level of limiting similaritythey must be different from one another in some fundamental way, otherwise one species would competitively exclude the other.[28] Despite this, the cumulative effect of additional species in an ecosystem is not linearadditional species may enhance nitrogen retention, for example, but beyond some level of species richness, additional species may have little additive effect.[27]

The addition (or loss) of species which are ecologically similar to those already present in an ecosystem tends to only have a small effect on ecosystem function. Ecologically distinct species, on the other hand, have a much larger effect. Similarly, dominant species have a large impact on ecosystem function, while rare species tend to have a small effect. Keystone species tend to have an effect on ecosystem function that is disproportionate to their abundance in an ecosystem.[27] Similarly, an ecosystem engineer is any organism that creates, significantly modifies, maintains or destroys a habitat.

Ecosystems are dynamic entities. They are subject to periodic disturbances and are in the process of recovering from some past disturbance.[10] When a perturbation occurs, an ecoystem responds by moving away from its initial state. The tendency of an ecosystem to remain close to its equilibrium state, despite that disturbance, is termed its resistance. On the other hand, the speed with which it returns to its initial state after disturbance is called its resilience.[10] Time plays a role in the development of soil from bare rock and the recovery of a community from disturbance.[9]

From one year to another, ecosystems experience variation in their biotic and abiotic environments. A drought, an especially cold winter and a pest outbreak all constitute short-term variability in environmental conditions. Animal populations vary from year to year, building up during resource-rich periods and crashing as they overshoot their food supply. These changes play out in changes in net primary production decomposition rates, and other ecosystem processes.[10] Longer-term changes also shape ecosystem processesthe forests of eastern North America still show legacies of cultivation which ceased 200 years ago, while methane production in eastern Siberian lakes is controlled by organic matter which accumulated during the Pleistocene.[10]

Disturbance also plays an important role in ecological processes. F. Stuart Chapin and coauthors define disturbance as “a relatively discrete event in time and space that alters the structure of populations, communities and ecosystems and causes changes in resources availability or the physical environment”.[29] This can range from tree falls and insect outbreaks to hurricanes and wildfires to volcanic eruptions. Such disturbances can cause large changes in plant, animal and microbe populations, as well soil organic matter content.[10] Disturbance is followed by succession, a “directional change in ecosystem structure and functioning resulting from biotically driven changes in resources supply.”[29]

The frequency and severity of disturbance determines the way it impacts ecosystem function. Major disturbance like a volcanic eruption or glacial advance and retreat leave behind soils that lack plants, animals or organic matter. Ecosystems that experience such disturbances undergo primary succession. Less severe disturbance like forest fires, hurricanes or cultivation result in secondary succession and a faster recovery.[10] More severe disturbance and more frequent disturbance result in longer recovery times.

Classifying ecosystems into ecologically homogeneous units is an important step towards effective ecosystem management.[30] There is no single, agreed-upon way to do this. A variety of systems exist, based on vegetation cover, remote sensing, and bioclimatic classification systems.[30]

Ecological land classification is a cartographical delineation or regionalisation of distinct ecological areas, identified by their geology, topography, soils, vegetation, climate conditions, living species, habitats, water resources, and sometimes also anthropic factors.[31]

Human activities are important in almost all ecosystems. Although humans exist and operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.[9]

Ecosystems provide a variety of goods and services upon which people depend.[32] Ecosystem goods include the “tangible, material products” of ecosystem processes such as food, construction material, medicinal plants.[33] They also include less tangible items like tourism and recreation, and genes from wild plants and animals that can be used to improve domestic species.[32]

Ecosystem services, on the other hand, are generally “improvements in the condition or location of things of value”.[33] These include things like the maintenance of hydrological cycles, cleaning air and water, the maintenance of oxygen in the atmosphere, crop pollination and even things like beauty, inspiration and opportunities for research.[32] While ecosystem goods have traditionally been recognized as being the basis for things of economic value, ecosystem services tend to be taken for granted.[33]

When natural resource management is applied to whole ecosystems, rather than single species, it is termed ecosystem management.[34] Although definitions of ecosystem management abound, there is a common set of principles which underlie these definitions.[35] A fundamental principle is the long-term sustainability of the production of goods and services by the ecosystem;[35] “intergenerational sustainability [is] a precondition for management, not an afterthought”.[32]

While ecosystem management can be used as part of a plan for wilderness conservation, it can also be used in intensively managed ecosystems[32] (see, for example, agroecosystem and close to nature forestry).

As human populations and per capita consumption grow, so do the resource demands imposed on ecosystems and the impacts of the human ecological footprint. Natural resources are vulnerable and limited. The environmental impacts of anthropogenic actions are becoming more apparent. Problems for all ecosystems include: environmental pollution, climate change and biodiversity loss. For terrestrial ecosystems further threats include air pollution, soil degradation, and deforestation. For aquatic ecosystems threats include also unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollution, microplastics pollution, water pollution, and building on coastal areas.[36]

Society is increasingly becoming aware that ecosystem services are not only limited, but also that they are threatened by human activities. The need to better consider long-term ecosystem health and its role in enabling human habitation and economic activity is urgent. To help inform decision-makers, many ecosystem services are being assigned economic values, often based on the cost of replacement with anthropogenic alternatives. The ongoing challenge of prescribing economic value to nature, for example through biodiversity banking, is prompting transdisciplinary shifts in how we recognize and manage the environment, social responsibility, business opportunities, and our future as a species.[citation needed]

The term “ecosystem” was first used in 1935 in a publication by British ecologist Arthur Tansley.[fn 1][37] Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment.[38] He later refined the term, describing it as “The whole system, … including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment”.[39] Tansley regarded ecosystems not simply as natural units, but as “mental isolates”.[39] Tansley later defined the spatial extent of ecosystems using the term ecotope.[40]

G. Evelyn Hutchinson, a limnologist who was a contemporary of Tansley’s, combined Charles Elton’s ideas about trophic ecology with those of Russian geochemist Vladimir Vernadsky. As a result he suggested that mineral nutrient availability in a lake limited algal production. This would, in turn, limit the abundance of animals that feed on algae. Raymond Lindeman took these ideas further to suggest that the flow of energy through a lake was the primary driver of the ecosystem. Hutchinson’s students, brothers Howard T. Odum and Eugene P. Odum, further developed a “systems approach” to the study of ecosystems. This allowed them to study the flow of energy and material through ecological systems.[38]

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Ecosystem – Wikipedia

Ecosystem – Wikipedia

This article is about natural ecosystems. For the term used in man-made systems, see Digital ecosystem.

An ecosystem is a community made up of living organisms(living things) and nonliving components such as air, water and mineral soil.[2] Ecosystems may be studied either as contingent collections of plants and animals, or as structured systems and communities that are governed by general rules.[3] The biotic and abiotic components interact through nutrient cycles and energy flows.[4] Ecosystems include a network of interactions among organisms, and between organisms and their environment.[5] Ecosystems can be of any size but one ecosystem has a specific, limited space.[6] Some scientists view the entire planet as one ecosystem.[7]

Energy, water, nitrogen and soil minerals are other essential abiotic components of an ecosystem. The energy that flows through ecosystems comes primarily from the sun, through photosynthesis. Photosynthesis also captures carbon dioxide from the atmosphere. Animals also play an important role in the movement of matter and energy through ecoystems. They influence the amount of plant and microbial biomass that lives in the system. As organic matter dies, decomposers release carbon back to the atmosphere. This process also facilitates nutrient cycling by converting nutrients stored in dead biomass back to a form that can be used again by plants and other microbes.[8]

Ecosystems are controlled both by external and internal factors. External factors such as climate, the parent material that forms the soil, topography and time have a big impact on ecosystems, but they are not themselves influenced by the ecosystem.[9] Ecosystems are dynamic: they are subject to periodic disturbances and are in the process of recovering from past disturbances.[10] Internal factors are different: They not only control ecosystem processes but are also controlled by them. Internal factors are subject to feedback loops.[9]

Humans operate within ecosystems. The effects of human activities can influence internal and external factors.[9] Global warming is an example of a cumulative impact of human activities. Ecosystems provide benefits, called “ecosystem services”, which people depend on for their livelihood. Ecosystem management is more efficient than trying to manage individual species.

There is no single definition of what constitutes an ecosystem.[3] German ecologist Ernst-Detlef Schulze and coauthors defined an ecosystem as an area which is “uniform regarding the biological turnover, and contains all the fluxes above and below the ground area under consideration.” They explicitly reject Gene Likens’ use of entire river catchments as “too wide a demarcation” to be a single ecosystem, given the level of heterogeneity within such an area.[11] Other authors have suggested that an ecosystem can encompass a much larger area, even the whole planet.[7] Schulze and coauthors also rejected the idea that a single rotting log could be studied as an ecosystem because the size of the flows between the log and its surroundings are too large, relative to the proportion cycles within the log.[11] Philosopher of science Mark Sagoff considers the failure to define “the kind of object it studies” to be an obstacle to the development of theory in ecosystem ecology.[3]

Ecosystems can be studied through a variety of approachestheoretical studies, studies monitoring specific ecosystems over long periods of time, those that look at differences between ecosystems to elucidate how they work and direct manipulative experimentation.[12] Studies can be carried out at a variety of scales, from microcosms and mesocosms which serve as simplified representations of ecosystems, through whole-ecosystem studies.[13] American ecologist Stephen R. Carpenter has argued that microcosm experiments can be “irrelevant and diversionary” if they are not carried out in conjunction with field studies carried out at the ecosystem scale, because microcosm experiments often fail to accurately predict ecosystem-level dynamics.[14]

The Hubbard Brook Ecosystem Study, established in the White Mountains, New Hampshire in 1963, was the first successful attempt to study an entire watershed as an ecosystem. The study used stream chemistry as a means of monitoring ecosystem properties, and developed a detailed biogeochemical model of the ecosystem.[15] Long-term research at the site led to the discovery of acid rain in North America in 1972, and was able to document the consequent depletion of soil cations (especially calcium) over the next several decades.[16]

The term “ecosystem” is often used very imprecisely and linked with a descriptive term (adjective) even if those systems are rather biomes, not ecosystems.[citation needed] Examples include: terrestrial ecosystem or aquatic ecosystems. Aquatic ecosystems are split into marine ecosystems (Large marine ecosystem is another term used) and freshwater ecosystems.

Ecosystems are controlled both by external and internal factors. External factors, also called state factors, control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem. The most important of these is climate.[9] Climate determines the biome in which the ecosystem is embedded. Rainfall patterns and temperature seasonality determine the amount of water available to the ecosystem and the supply of energy available (by influencing photosynthesis).[9]

Parent material, the underlying geological material that gives rise to soils, determines the nature of the soils present, and influences the supply of mineral nutrients. Topography also controls ecosystem processes by affecting things like microclimate, soil development and the movement of water through a system. This may be the difference between the ecosystem present in wetland situated in a small depression on the landscape, and one present on an adjacent steep hillside.[9]

Other external factors that play an important role in ecosystem functioning include time and potential biota. Similarly, the set of organisms that can potentially be present in an area can also have a major impact on ecosystems. Ecosystems in similar environments that are located in different parts of the world can end up doing things very differently simply because they have different pools of species present.[9] The introduction of non-native species can cause substantial shifts in ecosystem function.

Unlike external factors, internal factors in ecosystems not only control ecosystem processes, but are also controlled by them. Consequently, they are often subject to feedback loops.[9] While the resource inputs are generally controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading.[9] Other factors like disturbance, succession or the types of species present are also internal factors.

Primary production is the production of organic matter from inorganic carbon sources. This mainly occurs through photosynthesis. The energy incorporated through this process supports life on earth, while the carbon makes up much of the organic matter in living and dead biomass, soil carbon and fossil fuels. It also drives the carbon cycle, which influences global climate via the greenhouse effect.

Through the process of photosynthesis, plants capture energy from light and use it to combine carbon dioxide and water to produce carbohydrates and oxygen. The photosynthesis carried out by all the plants in an ecosystem is called the gross primary production (GPP).[17] About 4860% of the GPP is consumed in plant respiration.

The remainder, that portion of GPP that is not used up by respiration, is known as the net primary production (NPP).[18]

Energy and carbon enter ecosystems through photosynthesis, are incorporated into living tissue, transferred to other organisms that feed on the living and dead plant matter, and eventually released through respiration.[18]

The carbon and energy incorporated into plant tissues (net primary production) is either consumed by animals while the plant is alive, or it remains uneaten when the plant tissue dies and becomes detritus. In terrestrial ecosystems, roughly 90% of the net primary production ends up being broken down by decomposers. The remainder is either consumed by animals while still alive and enters the plant-based trophic system, or it is consumed after it has died, and enters the detritus-based trophic system.

In aquatic systems, the proportion of plant biomass that gets consumed by herbivores is much higher.[19]In trophic systems photosynthetic organisms are the primary producers. The organisms that consume their tissues are called primary consumers or secondary producersherbivores. Organisms which feed on microbes (bacteria and fungi) are termed microbivores. Animals that feed on primary consumerscarnivoresare secondary consumers. Each of these constitutes a trophic level.[19]

The sequence of consumptionfrom plant to herbivore, to carnivoreforms a food chain. Real systems are much more complex than thisorganisms will generally feed on more than one form of food, and may feed at more than one trophic level. Carnivores may capture some prey which are part of a plant-based trophic system and others that are part of a detritus-based trophic system (a bird that feeds both on herbivorous grasshoppers and earthworms, which consume detritus). Real systems, with all these complexities, form food webs rather than food chains.[19]

Ecosystem ecology studies “the flow of energy and materials through organisms and the physical environment”. It seeks to understand the processes which govern the stocks of material and energy in ecosystems, and the flow of matter and energy through them. The study of ecosystems can cover 10 orders of magnitude, from the surface layers of rocks to the surface of the planet.[20]

The carbon and nutrients in dead organic matter are broken down by a group of processes known as decomposition. This releases nutrients that can then be re-used for plant and microbial production, and returns carbon dioxide to the atmosphere (or water) where it can be used for photosynthesis. In the absence of decomposition, dead organic matter would accumulate in an ecosystem, and nutrients and atmospheric carbon dioxide would be depleted.[21] Approximately 90% of terrestrial net primary production goes directly from plant to decomposer.[19]

Decomposition processes can be separated into three categoriesleaching, fragmentation and chemical alteration of dead material.

As water moves through dead organic matter, it dissolves and carries with it the water-soluble components. These are then taken up by organisms in the soil, react with mineral soil, or are transported beyond the confines of the ecosystem (and are considered lost to it).[21] Newly shed leaves and newly dead animals have high concentrations of water-soluble components, and include sugars, amino acids and mineral nutrients. Leaching is more important in wet environments, and much less important in dry ones.[21]

Fragmentation processes break organic material into smaller pieces, exposing new surfaces for colonization by microbes. Freshly shed leaf litter may be inaccessible due to an outer layer of cuticle or bark, and cell contents are protected by a cell wall. Newly dead animals may be covered by an exoskeleton. Fragmentation processes, which break through these protective layers, accelerate the rate of microbial decomposition.[21] Animals fragment detritus as they hunt for food, as does passage through the gut. Freeze-thaw cycles and cycles of wetting and drying also fragment dead material.[21]

The chemical alteration of dead organic matter is primarily achieved through bacterial and fungal action. Fungal hyphae produce enzymes which can break through the tough outer structures surrounding dead plant material. They also produce enzymes which break down lignin, which allows them access to both cell contents and to the nitrogen in the lignin. Fungi can transfer carbon and nitrogen through their hyphal networks and thus, unlike bacteria, are not dependent solely on locally available resources.[21]

Decomposition rates vary among ecosystems. The rate of decomposition is governed by three sets of factorsthe physical environment (temperature, moisture and soil properties), the quantity and quality of the dead material available to decomposers, and the nature of the microbial community itself.[22] Temperature controls the rate of microbial respiration; the higher the temperature, the faster microbial decomposition occurs. It also affects soil moisture, which slows microbial growth and reduces leaching. Freeze-thaw cycles also affect decompositionfreezing temperatures kill soil microorganisms, which allows leaching to play a more important role in moving nutrients around. This can be especially important as the soil thaws in the spring, creating a pulse of nutrients which become available.[22]

Decomposition rates are low under very wet or very dry conditions. Decomposition rates are highest in wet, moist conditions with adequate levels of oxygen. Wet soils tend to become deficient in oxygen (this is especially true in wetlands), which slows microbial growth. In dry soils, decomposition slows as well, but bacteria continue to grow (albeit at a slower rate) even after soils become too dry to support plant growth.

Ecosystems continually exchange energy and carbon with the wider environment. Mineral nutrients, on the other hand, are mostly cycled back and forth between plants, animals, microbes and the soil. Most nitrogen enters ecosystems through biological nitrogen fixation, is deposited through precipitation, dust, gases or is applied as fertilizer.[23]

Since most terrestrial ecosystems are nitrogen-limited, nitrogen cycling is an important control on ecosystem production.[23]

Until modern times, nitrogen fixation was the major source of nitrogen for ecosystems. Nitrogen fixing bacteria either live symbiotically with plants, or live freely in the soil. The energetic cost is high for plants which support nitrogen-fixing symbiontsas much as 25% of gross primary production when measured in controlled conditions. Many members of the legume plant family support nitrogen-fixing symbionts. Some cyanobacteria are also capable of nitrogen fixation. These are phototrophs, which carry out photosynthesis. Like other nitrogen-fixing bacteria, they can either be free-living or have symbiotic relationships with plants.[23] Other sources of nitrogen include acid deposition produced through the combustion of fossil fuels, ammonia gas which evaporates from agricultural fields which have had fertilizers applied to them, and dust.[23] Anthropogenic nitrogen inputs account for about 80% of all nitrogen fluxes in ecosystems.[23]

When plant tissues are shed or are eaten, the nitrogen in those tissues becomes available to animals and microbes. Microbial decomposition releases nitrogen compounds from dead organic matter in the soil, where plants, fungi and bacteria compete for it. Some soil bacteria use organic nitrogen-containing compounds as a source of carbon, and release ammonium ions into the soil. This process is known as nitrogen mineralization. Others convert ammonium to nitrite and nitrate ions, a process known as nitrification. Nitric oxide and nitrous oxide are also produced during nitrification.[23] Under nitrogen-rich and oxygen-poor conditions, nitrates and nitrites are converted to nitrogen gas, a process known as denitrification.[23]

Other important nutrients include phosphorus, sulfur, calcium, potassium, magnesium and manganese.[24] Phosphorus enters ecosystems through weathering. As ecosystems age this supply diminishes, making phosphorus-limitation more common in older landscapes (especially in the tropics).[24] Calcium and sulfur are also produced by weathering, but acid deposition is an important source of sulfur in many ecosystems. Although magnesium and manganese are produced by weathering, exchanges between soil organic matter and living cells account for a significant portion of ecosystem fluxes. Potassium is primarily cycled between living cells and soil organic matter.[24]

Biodiversity plays an important role in ecosystem functioning.[26] The reason for this is that ecosystem processes are driven by the number of species in an ecosystem, the exact nature of each individual species, and the relative abundance organisms within these species.[27] Ecosystem processes are broad generalizations that actually take place through the actions of individual organisms. The nature of the organismsthe species, functional groups and trophic levels to which they belongdictates the sorts of actions these individuals are capable of carrying out, and the relative efficiency with which they do so.

Ecological theory suggests that in order to coexist, species must have some level of limiting similaritythey must be different from one another in some fundamental way, otherwise one species would competitively exclude the other.[28] Despite this, the cumulative effect of additional species in an ecosystem is not linearadditional species may enhance nitrogen retention, for example, but beyond some level of species richness, additional species may have little additive effect.[27]

The addition (or loss) of species which are ecologically similar to those already present in an ecosystem tends to only have a small effect on ecosystem function. Ecologically distinct species, on the other hand, have a much larger effect. Similarly, dominant species have a large impact on ecosystem function, while rare species tend to have a small effect. Keystone species tend to have an effect on ecosystem function that is disproportionate to their abundance in an ecosystem.[27] Similarly, an ecosystem engineer is any organism that creates, significantly modifies, maintains or destroys a habitat.

Ecosystems are dynamic entities. They are subject to periodic disturbances and are in the process of recovering from some past disturbance.[10] When a perturbation occurs, an ecoystem responds by moving away from its initial state. The tendency of an ecosystem to remain close to its equilibrium state, despite that disturbance, is termed its resistance. On the other hand, the speed with which it returns to its initial state after disturbance is called its resilience.[10] Time plays a role in the development of soil from bare rock and the recovery of a community from disturbance.[9]

From one year to another, ecosystems experience variation in their biotic and abiotic environments. A drought, an especially cold winter and a pest outbreak all constitute short-term variability in environmental conditions. Animal populations vary from year to year, building up during resource-rich periods and crashing as they overshoot their food supply. These changes play out in changes in net primary production decomposition rates, and other ecosystem processes.[10] Longer-term changes also shape ecosystem processesthe forests of eastern North America still show legacies of cultivation which ceased 200 years ago, while methane production in eastern Siberian lakes is controlled by organic matter which accumulated during the Pleistocene.[10]

Disturbance also plays an important role in ecological processes. F. Stuart Chapin and coauthors define disturbance as “a relatively discrete event in time and space that alters the structure of populations, communities and ecosystems and causes changes in resources availability or the physical environment”.[29] This can range from tree falls and insect outbreaks to hurricanes and wildfires to volcanic eruptions. Such disturbances can cause large changes in plant, animal and microbe populations, as well soil organic matter content.[10] Disturbance is followed by succession, a “directional change in ecosystem structure and functioning resulting from biotically driven changes in resources supply.”[29]

The frequency and severity of disturbance determines the way it impacts ecosystem function. Major disturbance like a volcanic eruption or glacial advance and retreat leave behind soils that lack plants, animals or organic matter. Ecosystems that experience such disturbances undergo primary succession. Less severe disturbance like forest fires, hurricanes or cultivation result in secondary succession and a faster recovery.[10] More severe disturbance and more frequent disturbance result in longer recovery times.

Classifying ecosystems into ecologically homogeneous units is an important step towards effective ecosystem management.[30] There is no single, agreed-upon way to do this. A variety of systems exist, based on vegetation cover, remote sensing, and bioclimatic classification systems.[30]

Ecological land classification is a cartographical delineation or regionalisation of distinct ecological areas, identified by their geology, topography, soils, vegetation, climate conditions, living species, habitats, water resources, and sometimes also anthropic factors.[31]

Human activities are important in almost all ecosystems. Although humans exist and operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.[9]

Ecosystems provide a variety of goods and services upon which people depend.[32] Ecosystem goods include the “tangible, material products” of ecosystem processes such as food, construction material, medicinal plants.[33] They also include less tangible items like tourism and recreation, and genes from wild plants and animals that can be used to improve domestic species.[32]

Ecosystem services, on the other hand, are generally “improvements in the condition or location of things of value”.[33] These include things like the maintenance of hydrological cycles, cleaning air and water, the maintenance of oxygen in the atmosphere, crop pollination and even things like beauty, inspiration and opportunities for research.[32] While ecosystem goods have traditionally been recognized as being the basis for things of economic value, ecosystem services tend to be taken for granted.[33]

When natural resource management is applied to whole ecosystems, rather than single species, it is termed ecosystem management.[34] Although definitions of ecosystem management abound, there is a common set of principles which underlie these definitions.[35] A fundamental principle is the long-term sustainability of the production of goods and services by the ecosystem;[35] “intergenerational sustainability [is] a precondition for management, not an afterthought”.[32]

While ecosystem management can be used as part of a plan for wilderness conservation, it can also be used in intensively managed ecosystems[32] (see, for example, agroecosystem and close to nature forestry).

As human populations and per capita consumption grow, so do the resource demands imposed on ecosystems and the impacts of the human ecological footprint. Natural resources are vulnerable and limited. The environmental impacts of anthropogenic actions are becoming more apparent. Problems for all ecosystems include: environmental pollution, climate change and biodiversity loss. For terrestrial ecosystems further threats include air pollution, soil degradation, and deforestation. For aquatic ecosystems threats include also unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollution, microplastics pollution, water pollution, and building on coastal areas.[36]

Society is increasingly becoming aware that ecosystem services are not only limited, but also that they are threatened by human activities. The need to better consider long-term ecosystem health and its role in enabling human habitation and economic activity is urgent. To help inform decision-makers, many ecosystem services are being assigned economic values, often based on the cost of replacement with anthropogenic alternatives. The ongoing challenge of prescribing economic value to nature, for example through biodiversity banking, is prompting transdisciplinary shifts in how we recognize and manage the environment, social responsibility, business opportunities, and our future as a species.[citation needed]

The term “ecosystem” was first used in 1935 in a publication by British ecologist Arthur Tansley.[fn 1][37] Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment.[38] He later refined the term, describing it as “The whole system, … including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment”.[39] Tansley regarded ecosystems not simply as natural units, but as “mental isolates”.[39] Tansley later defined the spatial extent of ecosystems using the term ecotope.[40]

G. Evelyn Hutchinson, a limnologist who was a contemporary of Tansley’s, combined Charles Elton’s ideas about trophic ecology with those of Russian geochemist Vladimir Vernadsky. As a result he suggested that mineral nutrient availability in a lake limited algal production. This would, in turn, limit the abundance of animals that feed on algae. Raymond Lindeman took these ideas further to suggest that the flow of energy through a lake was the primary driver of the ecosystem. Hutchinson’s students, brothers Howard T. Odum and Eugene P. Odum, further developed a “systems approach” to the study of ecosystems. This allowed them to study the flow of energy and material through ecological systems.[38]

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Ecosystem – Wikipedia

Ecosystem services – Wikipedia

Ecosystem services are the many and varied benefits that humans freely gain from the natural environment and from properly-functioning ecosystems. Such ecosystems include, for example, agroecosystems, forest ecosystems, grassland ecosystems and aquatic ecosystems. Collectively, these benefits are becoming known as ‘ecosystem services’, and are often integral to the provisioning of clean drinking water, the decomposition of wastes, and the natural pollination of crops and other plants.

While scientists and environmentalists have discussed ecosystem services implicitly for decades, the Millennium Ecosystem Assessment (MA) in the early 2000s popularized the concept.[1] There, ecosystem services are grouped into four broad categories: provisioning, such as the production of food and water; regulating, such as the control of climate and disease; supporting, such as nutrient cycles and crop pollination; and cultural, such as spiritual and recreational benefits. To help inform decision-makers, many ecosystem services are being assigned economic values.

While the notion of human dependence on Earth’s ecosystems reaches to the start of Homo sapiens’ existence, the term ‘natural capital’ was first coined by E.F. Schumacher in 1973 in his book Small is Beautiful [2]. Recognition of how ecosystems could provide complex services to humankind date back to at least Plato (c. 400 BC) who understood that deforestation could lead to soil erosion and the drying of springs.[3][pageneeded] Modern ideas of ecosystem services probably began when Marsh challenged in 1864 the idea that Earth’s natural resources are unbounded by pointing out changes in soil fertility in the Mediterranean.[4][pageneeded] It was not until the late 1940s that three key authorsHenry Fairfield Osborn, Jr,[5] William Vogt,[6] and Aldo Leopold [7]promoted recognition of human dependence on the environment.

In 1956, Paul Sears drew attention to the critical role of the ecosystem in processing wastes and recycling nutrients.[8] In 1970, Paul Ehrlich and Rosa Weigert called attention to “ecological systems” in their environmental science textbook[9] and “the most subtle and dangerous threat to man’s existence… the potential destruction, by man’s own activities, of those ecological systems upon which the very existence of the human species depends”.

The term “environmental services” was introduced in a 1970 report of the Study of Critical Environmental Problems,[10] which listed services including insect pollination, fisheries, climate regulation and flood control. In following years, variations of the term were used, but eventually ‘ecosystem services’ became the standard in scientific literature.[11]

The ecosystem services concept has continued to expand and includes socio-economic and conservation objectives, which are discussed below. A history of the concepts and terminology of ecosystem services as of 1997, can be found in Daily’s book “Nature’s Services: Societal Dependence on Natural Ecosystems”.[3]

While Gretchen Daily’s original definition distinguished between ecosystem goods and ecosystem services, Robert Costanza and colleagues’ later work and that of the Millennium Ecosystem Assessment lumped all of these together as ecosystem services.[12][13]

Per the 2006 Millennium Ecosystem Assessment (MA), ecosystem services are “the benefits people obtain from ecosystems”. The MA also delineated the four categories of ecosystem servicessupporting, provisioning, regulating and culturaldiscussed below.

By 2010, there had evolved various working definitions and descriptions of ecosystem services in the literature.[14] To prevent double counting in ecosystem services audits, for instance, The Economics of Ecosystems and Biodiversity (TEEB) replaced “Supporting Services” in the MA with “Habitat Services” and “ecosystem functions”, defined as “a subset of the interactions between ecosystem structure and processes that underpin the capacity of an ecosystem to provide goods and services”.[15]

The Millennium Ecosystem Assessment (MA) report 2005 defines Ecosystem services as benefits people obtain from ecosystems and distinguishes four categories of ecosystem services, where the so-called supporting services are regarded as the basis for the services of the other three categories.[1]

These include services such as nutrient recycling, primary production and soil formation.[16] These services make it possible for the ecosystems to provide services such as food supply, flood regulation, and water purification.

There is discussion as to how the concept of cultural ecosystem services can be operationalized. A good review of approaches in landscape aesthetics, cultural heritage, outdoor recreation, and spiritual significance to define and assess cultural values of our environment so that they fit into the ecosystem services approach is given by Daniel et al.[17] who vote for models that explicitly link ecological structures and functions with cultural values and benefits. There also is a fundamental critique of the concept of cultural ecosystem services that builds on three arguments:[18]

The following examples illustrate the relationships between humans and natural ecosystems through the services derived from them:

Understanding of ecosystem services requires a strong foundation in ecology, which describes the underlying principles and interactions of organisms and the environment. Since the scales at which these entities interact can vary from microbes to landscapes, milliseconds to millions of years, one of the greatest remaining challenges is the descriptive characterization of energy and material flow between them. For example, the area of a forest floor, the detritus upon it, the microorganisms in the soil and characteristics of the soil itself will all contribute to the abilities of that forest for providing ecosystem services like carbon sequestration, water purification, and erosion prevention to other areas within the watershed. Note that it is often possible for multiple services to be bundled together and when benefits of targeted objectives are secured, there may also be ancillary benefitsthe same forest may provide habitat for other organisms as well as human recreation, which are also ecosystem services.

The complexity of Earth’s ecosystems poses a challenge for scientists as they try to understand how relationships are interwoven among organisms, processes and their surroundings. As it relates to human ecology, a suggested research agenda [22] for the study of ecosystem services includes the following steps:

Recently, a technique has been developed to improve and standardize the evaluation of ESP functionality by quantifying the relative importance of different species in terms of their efficiency and abundance.[28] Such parameters provide indications of how species respond to changes in the environment (i.e. predators, resource availability, climate) and are useful for identifying species that are disproportionately important at providing ecosystem services. However, a critical drawback is that the technique does not account for the effects of interactions, which are often both complex and fundamental in maintaining an ecosystem and can involve species that are not readily detected as a priority. Even so, estimating the functional structure of an ecosystem and combining it with information about individual species traits can help us understand the resilience of an ecosystem amidst environmental change.

Many ecologists also believe that the provision of ecosystem services can be stabilized with biodiversity. Increasing biodiversity also benefits the variety of ecosystem services available to society. Understanding the relationship between biodiversity and an ecosystem’s stability is essential to the management of natural resources and their services.

The concept of ecological redundancy is sometimes referred to as functional compensation and assumes that more than one species performs a given role within an ecosystem.[29] More specifically, it is characterized by a particular species increasing its efficiency at providing a service when conditions are stressed in order to maintain aggregate stability in the ecosystem.[30] However, such increased dependence on a compensating species places additional stress on the ecosystem and often enhances its susceptibility to subsequent disturbance[citation needed]. The redundancy hypothesis can be summarized as “species redundancy enhances ecosystem resilience”.[31]

Another idea uses the analogy of rivets in an airplane wing to compare the exponential effect the loss of each species will have on the function of an ecosystem; this is sometimes referred to as rivet popping.[32] If only one species disappears, the loss of the ecosystem’s efficiency as a whole is relatively small; however, if several species are lost, the system essentially collapsessimilar to an airplane that lost too many rivets. The hypothesis assumes that species are relatively specialized in their roles and that their ability to compensate for one another is less than in the redundancy hypothesis. As a result, the loss of any species is critical to the performance of the ecosystem. The key difference is the rate at which the loss of species affects total ecosystem functioning.

A third explanation, known as the portfolio effect, compares biodiversity to stock holdings, where diversification minimizes the volatility of the investment, or in this case, the risk of instability of ecosystem services.[33] This is related to the idea of response diversity where a suite of species will exhibit differential responses to a given environmental perturbation. When considered together, they create a stabilizing function that preserves the integrity of a service.[34]

Several experiments have tested these hypotheses in both the field and the lab. In ECOTRON, a laboratory in the UK where many of the biotic and abiotic factors of nature can be simulated, studies have focused on the effects of earthworms and symbiotic bacteria on plant roots.[32] These laboratory experiments seem to favor the rivet hypothesis. However, a study on grasslands at Cedar Creek Reserve in Minnesota supports the redundancy hypothesis, as have many other field studies.[35]

There are questions regarding the environmental and economic values of ecosystem services.[36] Some people may be unaware of the environment in general and humanity’s interrelatedness with the natural environment, which may cause misconceptions. Although environmental awareness is rapidly improving in our contemporary world, ecosystem capital and its flow are still poorly understood, threats continue to impose, and we suffer from the so-called ‘tragedy of the commons’.[37] Many efforts to inform decision-makers of current versus future costs and benefits now involve organizing and translating scientific knowledge to economics, which articulate the consequences of our choices in comparable units of impact on human well-being.[38] An especially challenging aspect of this process is that interpreting ecological information collected from one spatial-temporal scale does not necessarily mean it can be applied at another; understanding the dynamics of ecological processes relative to ecosystem services is essential in aiding economic decisions.[39] Weighting factors such as a service’s irreplaceability or bundled services can also allocate economic value such that goal attainment becomes more efficient.

The economic valuation of ecosystem services also involves social communication and information, areas that remain particularly challenging and are the focus of many researchers.[40] In general, the idea is that although individuals make decisions for any variety of reasons, trends reveal the aggregative preferences of a society, from which the economic value of services can be inferred and assigned. The six major methods for valuing ecosystem services in monetary terms are:[41]

A peer-reviewed study published in 1997 estimated the value of the world’s ecosystem services and natural capital to be between US$1654 trillion per year, with an average of US$33 trillion per year.[42] However, Salles (2011) indicates ‘The total value of biodiversity is infinite, so having debate about what is the total value of nature is actually pointless because we can’t live without it’.

Although monetary pricing continues with respect to the valuation of ecosystem services, the challenges in policy implementation and management are significant and multitudinous. The administration of common pool resources is a subject of extensive academic pursuit.[43][44][45][46][47] From defining the problems to finding solutions that can be applied in practical and sustainable ways, there is much to overcome. Considering options must balance present and future human needs, and decision-makers must frequently work from valid but incomplete information. Existing legal policies are often considered insufficient since they typically pertain to human health-based standards that are mismatched with necessary means to protect ecosystem health and services. To improve the information available, one suggestion has involved the implementation of an Ecosystem Services Framework (ESF[48]), which integrates the biophysical and socio-economic dimensions of protecting the environment and is designed to guide institutions through multidisciplinary information and jargon, helping to direct strategic choices.

Novel and expedient methods are needed to deal with managing Earth’s ecosystem services. Local to regional collective management efforts might be considered appropriate for services like crop pollination or resources like water.[22][43] Another approach that has become increasingly popular over the last decade is the marketing of ecosystem services protection. Payment and trading of services is an emerging worldwide small-scale solution where one can acquire credits for activities such as sponsoring the protection of carbon sequestration sources or the restoration of ecosystem service providers. In some cases, banks for handling such credits have been established and conservation companies have even gone public on stock exchanges, defining an evermore parallel link with economic endeavors and opportunities for tying into social perceptions.[38] However, crucial for implementation are clearly defined land rights, which is often lacking in many developing countries.[49] In particular, many forest-rich developing countries suffering deforestation experience conflict between different forest stakeholders.[49] In addition, concerns for such global transactions include inconsistent compensation for services or resources sacrificed elsewhere and misconceived warrants for irresponsible use. Another approach has been focused on protecting ecosystem service ‘hotspots’. Recognition that the conservation of many ecosystem services aligns with more traditional conservation goals (i.e. biodiversity) has led to the suggested merging of objectives for maximizing their mutual success. This may be particularly strategic when employing networks that permit the flow of services across landscapes, and might also facilitate securing the financial means to protect services through a diversification of investors.[50][51]

For example, in recent years there has been interest in the valuation of ecosystem services provided by shellfish production and restoration.[52] A keystone species, low in the food chain, bivalve shellfish such as oysters support a complex community of species by performing a number of functions essential to the diverse array of species that surround them. There is also increasing recognition that some shellfish species may impact or control many ecological processes; so much so that they are included on the list of “ecosystem engineers”organisms that physically, biologically or chemically modify the environment around them in ways that influence the health of other organisms.[53] Many of the ecological functions and processes performed or affected by shellfish contribute to human well-being by providing a stream of valuable ecosystem services over time by filtering out particulate materials and potentially mitigating water quality issues by controlling excess nutrients in the water.

Ecosystem-based adaptation or EbA is an emerging strategy for community development and environmental management that seeks to use an ecosystem services framework to help communities adapt to the effects of climate change. The Convention on Biological Diversity currently defines Ecosystem-Based Adaptation as “the use of biodiversity and ecosystem services to help people adapt to the adverse effects of climate change”, which includes the use of “sustainable management, conservation and restoration of ecosystems, as part of an overall adaptation strategy that takes into account the multiple social, economic and cultural co-benefits for local communities”.[54]

In 2001, the Millennium Ecosystem Assessment announced that humanity’s impact on the natural world was increasing to levels never before seen, and that the degradation of the planet’s ecosystems would become a major barrier to achieving the Millennium Development Goals. In recognition of this fact, Ecosystem-Based Adaptation seeks to use the restoration of ecosystems as a stepping-stone to improving the quality of life in communities experiencing the impacts of climate change. Specifically, this involves the restoration of ecosystems that provide the community with essential services, such as the provisioning of food and water and protection from storm surges and flooding. EbA interventions typically combine elements of both climate change mitigation and adaptation to global warming to help address the community’s current and future needs.[55]

Collaborative planning between scientists, policy makers, and community members is an essential element of Ecosystem-Based Adaptation. By drawing on the expertise of outside experts and local residents alike, EbA seeks to develop unique solutions to unique problems, rather than simply replicating past projects.[54]

Ecosystem services are defined as the gains acquired by humankind from surroundings ecosystems. Four different types of ecosystem services have been distinguished by the scientific body: regulating services, provisioning services, cultural services and supporting services. An ecosystem does not necessarily offer all four types of services simultaneously; but given the intricate nature of any ecosystem, it is usually assumed that humans benefit from a combination of these services. The services offered by diverse types of ecosystems (forests, seas, coral reefs, mangroves, etc.) differ in nature and in consequence. In fact, some services directly affect the livelihood of neighboring human populations (such as fresh water, food or aesthetic value, etc.) while other services affect general environmental conditions by which humans are indirectly impacted (such as climate change, erosion regulation or natural hazard regulation, etc.).[56]

Estuarine and coastal ecosystems are both marine ecosystems. An estuary is defined as the area in which a river meets the sea or the ocean. The waters surrounding this area are predominantly salty waters or brackish waters; and the incoming river water is dynamically motioned by the tide. An estuary strip may be covered by populations of reed (or similar plants) and/or sandbanks (or similar form or land).[citation needed]

A coastal ecosystem occurs in areas where the sea or ocean waters meet the land.[citation needed]

Regulating services are the “benefits obtained from the regulation of ecosystem processes”.[57] In the case of coastal and estuarine ecosystems, these services include climate regulation, waste treatment and disease control and natural hazard regulation.

Both the biotic and abiotic ensembles of marine ecosystems play a role in climate regulation. They act as sponges when it comes to gases in the atmosphere, retaining large levels of CO2 and other greenhouse gases (methane and nitrous oxide). Marine plants also use CO2 for photosynthesis purposes and help in reducing the atmospheric CO2. The oceans and seas absorb the heat from the atmosphere and redistribute it through the means of water currents, and atmospheric processes, such as evaporation and the reflection of light allow for the cooling and warming of the overlying atmosphere. The ocean temperatures are thus imperative to the regulation of the atmospheric temperatures in any part of the world: “without the ocean, the Earth would be unbearably hot during the daylight hours and frigidly cold, if not frozen, at night”.[58]

Another service offered by marine ecosystem is the treatment of wastes, thus helping in the regulation of diseases. Wastes can be diluted and detoxified through transport across marine ecosystems; pollutants are removed from the environment and stored, buried or recycled in marine ecosystems: “Marine ecosystems break down organic waste through microbial communities that filter water, reduce/limit the effects of eutrophication, and break down toxic hydrocarbons into their basic components such as carbon dioxide, nitrogen, phosphorus, and water”.[58] The fact that waste is diluted with large volumes of water and moves with water currents leads to the regulation of diseases and the reduction of toxics in seafood.

Coastal and estuarine ecosystems act as buffer zones against natural hazards and environmental disturbances, such as floods, cyclones, tidal surges and storms. The role they play is to “[absorb] a portion of the impact and thus [lessen] its effect on the land”.[58] Wetlands, for example, and the vegetation it supports trees, root mats, etc. retain large amounts of water (surface water, snowmelt, rain, groundwater) and then slowly releases them back, decreasing the likeliness of floods.[59] Mangrove forests protect coastal shorelines from tidal erosion or erosion by currents; a process that was studied after the 1999 cyclone that hit India. Villages that were surrounded with mangrove forests encountered less damages than other villages that weren’t protected by mangroves.[60]

Provisioning services consist of all “the products obtained from ecosystems”. Marine ecosystems provide people with: wild & cultured seafood, fresh water, fiber & fuel and biochemical & genetic resources.[citation needed]

Humans consume a large number of products originating from the seas, whether as a nutritious product or for use in other sectors: “More than one billion people worldwide, or one-sixth of the global population, rely on fish as their main source of animal protein. In 2000, marine and coastal fisheries accounted for 12 per cent of world food production”.[61] Fish and other edible marine products primarily fish, shellfish, roe and seaweeds constitute for populations living along the coast the main elements of the local cultural diets, norms and traditions. A very pertinent example would be sushi, the national food of Japan, which consists mostly of different types of fish and seaweed.

Water bodies that are not highly concentrated in salts are referred to as ‘fresh water’ bodies. Fresh water may run through lakes, rivers and streams, to name a few; but it is most prominently found in the frozen state or as soil moisture or buried deep underground. Fresh water is not only important for the survival of humans, but also for the survival of all the existing species of animals, plants.[citation needed]

Marine creatures provide us with the raw materials needed for the manufacturing of clothing, building materials (lime extracted from coral reefs), ornamental items and personal-use items (luffas, art and jewelry): “The skin of marine mammals for clothing, gas deposits for energy production, lime (extracted from coral reefs) for building construction, and the timber of mangroves and coastal forests for shelter are some of the more familiar uses of marine organisms. Raw marine materials are utilized for non-essential goods as well, such as shells and corals in ornamental items”.[61] Humans have also referred to processes within marine environments for the production of renewable energy: using the power of waves or tidal power as a source of energy for the powering of a turbine, for example.[citation needed] Oceans and seas are used as sites for offshore oil and gas installations, offshore wind farms.[citation needed]

Biochemical resources are compounds extracted from marine organisms for use in medicines, pharmaceuticals, cosmetics and other biochemical products. Genetic resources are the genetic information found in marine organisms that would later on be used for animal and plant breeding and for technological advances in the biological field. These resources are either directly taken out from an organism such as fish oil as a source of omega3 , or used as a model for innovative man-made products: “such as the construction of fiber optics technology based on the properties of sponges. … Compared to terrestrial products, marine-sourced products tend to be more highly bioactive, likely due to the fact that marine organisms have to retain their potency despite being diluted in the surrounding sea-water”.[61]

Cultural services relate to the non-material world, as they benefit the benefit recreational, aesthetic, cognitive and spiritual activities, which are not easily quantifiable in monetary terms.[citation needed]

Marine environments have been used by many as an inspiration for their works of art, music, architecture, traditions… Water environments are spiritually important as a lot of people view them as a means for rejuvenation and change of perspective. Many also consider the water as being a part of their personality, especially if they have lived near it since they were kids: they associate it to fond memories and past experiences. Living near water bodies for a long time results in a certain set of water activities that become a ritual in the lives of people and of the culture in the region.[citation needed]

Sea sports are very popular among coastal populations: surfing, snorkeling, whale watching, kayaking, recreational fishing…a lot of tourists also travel to resorts close to the sea or rivers or lakes to be able to experience these activities, and relax near the water.[citation needed]

A lot can be learned from marine processes, environments and organisms that could be implemented into our daily actions and into the scientific domain. Although much is still yet to still be known about the ocean world: “by the extraordinary intricacy and complexity of the marine environment and how it is influenced by large spatial scales, time lags, and cumulative effects”.[58]

Supporting services are the services that allow for the other ecosystem services to be present. They have indirect impacts on humans that last over a long period of time. Several services can be considered as being both supporting services and regulating/cultural/provisioning services.[citation needed]

“Nutrient cycling refers to the storage, cycling, and maintenance of nutrients by organisms and their associated processes”. The ocean is a vast storage pool for these nutrients, such as carbon, nitrogen and phosphorus. The nutrients are absorbed by the basic organisms of the marine food web and are thus transferred from one organism to the other and from one ecosystem to the other. Nutrients are recycled through the life cycle of organisms as they die and decompose, releasing the nutrients into the neighboring environment. “The service of nutrient cycling eventually impacts all other ecosystem services as all living things require a constant supply of nutrients to survive”.[58]

Biologically mediated habitats are defined as being the habitats that living marine structures offer to other organisms.[62] These need not to be designed for the sole purpose of serving as a habitat, but happen to become living quarters whilst growing naturally. For example, coral reefs and mangrove forests are home to numerous species of fish, seaweed and shellfish… The importance of these habitats is that they allow for interactions between different species, aiding the provisioning of marine goods and services. They are also very important for the growth at the early life stages of marine species (breeding and bursary spaces), as they serve as a food source and as a shelter from predators.[citation needed]

Primary production refers to the production of organic matter, i.e., chemically bound energy, through processes such as photosynthesis and chemosynthesis. The organic matter produced by primary producers forms the basis of all food webs. Further, it generates oxygen (O2), a molecule necessary to sustain animals and humans.[63][64][65][66]

Ecosystem services degradation can pose a number of risks to corporate performance as well as provide business opportunities through ecosystem restoration and enhancement. Risks and opportunities include:

Many companies are not fully aware of the extent of their dependence and impact on ecosystems and the possible ramifications. Likewise, environmental management systems and environmental due diligence tools are more suited to handle “traditional” issues of pollution and natural resource consumption. Most focus on environmental impacts, not dependence. Several newly developed tools and methodologies can help the private sector value and assess ecosystem services. These include Our Ecosystem,[67] the Corporate Ecosystem Services Review (ESR),[68] Artificial Intelligence for Ecosystem Services (ARIES),[69] the Natural Value Initiative (NVI)[70] and InVEST (Integrated Valuation of Ecosystem Services & Tradeoffs) [71]

Ecosystem services decisions require making complex choices at the intersection of ecology, technology, society and the economy. The process of making ecosystem services decisions must consider the interaction of many types of information, honor all stakeholder viewpoints, including regulatory agencies, proposal proponents, decision makers, residents, NGOs, and measure the impacts on all four parts of the intersection. These decisions are usually spatial, always multi-objective, and based on uncertain data, models, and estimates. Often it is the combination of the best science combined with the stakeholder values, estimates and opinions that drive the process.[72]

One analytical study modeled the stakeholders as agents to support water resource management decisions in the Middle Rio Grande basin of New Mexico. This study focused on modeling the stakeholder inputs across a spatial decision, but ignored uncertainty.[73] Another study used Monte Carlo methods to exercise econometric models of landowner decisions in a study of the effects of land-use change. Here the stakeholder inputs were modeled as random effects to reflect the uncertainty.[74] A third study used a Bayesian decision support system to both model the uncertainty in the scientific information Bayes Nets and to assist collecting and fusing the input from stakeholders. This study was about siting wave energy devices off the Oregon Coast, but presents a general method for managing uncertain spatial science and stakeholder information in a decision making environment.[75] Remote sensing data and analyses can be used to assess the health and extent of land cover classes that provide ecosystem services, which aids in planning, management, monitoring of stakeholders’ actions, and communication between stakeholders.[76]

In Baltic countries scientists, nature conservationists and local authorities are implementing integrated planning approach for grassland ecosystems. They are developing Integrated Planning Tool that will be based on GIS (geographic information system) technology and put online that will help for planners to choose the best grassland management solution for concrete grassland. It will look holistically at the processes in the countryside and help to find best grassland management solutions by taking into account both natural and socioeconomic factors of the particular site.

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Ecosystem services – Wikipedia

Ecosystem – Wikipedia

This article is about natural ecosystems. For the term used in man-made systems, see Digital ecosystem.

An ecosystem can be defined as a community made up of living organisms and nonliving components such as air, water and mineral soil.[2] However, ecosystems can be defined in many ways.[3] The biotic and abiotic components interact through nutrient cycles and energy flows.[4] Ecosystems include a network of interactions among organisms, and between organisms and their environment.[5] Ecosystems can be of any size but one ecosystem has a specific, limited space.[6] Some scientists view the entire planet as one ecosystem.[7]

Energy, water, nitrogen and soil minerals are other essential abiotic components of an ecosystem. The energy that flows through ecosystems comes primarily from the sun, through photosynthesis. Photosynthesis also captures carbon dioxide from the atmosphere. Animals also play an important role in the movement of matter and energy through ecoystems. They influence the amount of plant and microbial biomass that lives in the system. As organic matter dies, decomposers release carbon back to the atmosphere. This process also facilitates nutrient cycling by converting nutrients stored in dead biomass back to a form that can be used again by plants and other microbes.[8]

Ecosystems are controlled both by external and internal factors. External factors such as climate, the parent material that forms the soil, topography and time have a big impact on ecosystems, but they are not themselves influenced by the ecosystem.[9] Ecosystems are dynamic: they are subject to periodic disturbances and are in the process of recovering from past disturbances.[10] Internal factors are different: They not only control ecosystem processes but are also controlled by them. Internal factors are subject to feedback loops.[9]

Humans operate within ecosystems. The effects of human activities can influence internal and external factors.[9] Global warming is an example of a cumulative impact of human activities. Ecosystems provide benefits, called “ecosystem services”, which people depend on for their livelihood. Ecosystem management is more efficient than trying to manage individual species.

There is no single definition of what constitutes an ecosystem.[3] German ecologist Ernst-Detlef Schulze and coauthors defined an ecosystem as an area which is “uniform regarding the biological turnover, and contains all the fluxes above and below the ground area under consideration.” They explicitly reject Gene Likens’ use of entire river catchments as “too wide a demarcation” to be a single ecosystem, given the level of heterogeneity within such an area.[11] Other authors have suggested that an ecosystem can encompass a much larger area, even the whole planet.[7] Schulze and coauthors also rejected the idea that a single rotting log could be studied as an ecosystem because the size of the flows between the log and its surroundings are too large, relative to the proportion cycles within the log.[11] Philosopher of science Mark Sagoff considers the failure to define “the kind of object it studies” to be an obstacle to the development of theory in ecosystem ecology.[3]

Ecosystems can be studied through a variety of approachestheoretical studies, studies monitoring specific ecosystems over long periods of time, those that look at differences between ecosystems to elucidate how they work and direct manipulative experimentation.[12] Studies can be carried out at a variety of scales, from microcosms and mesocosms which serve as simplified representations of ecosystems, through whole-ecosystem studies.[13] American ecologist Stephen R. Carpenter has argued that microcosm experiments can be “irrelevant and diversionary” if they are not carried out in conjunction with field studies carried out at the ecosystem scale, because microcosm experiments often fail to accurately predict ecosystem-level dynamics.[14]

The Hubbard Brook Ecosystem Study, established in the White Mountains, New Hampshire in 1963, was the first successful attempt to study an entire watershed as an ecosystem. The study used stream chemistry as a means of monitoring ecosystem properties, and developed a detailed biogeochemical model of the ecosystem.[15] Long-term research at the site led to the discovery of acid rain in North America in 1972, and was able to document the consequent depletion of soil cations (especially calcium) over the next several decades.[16]

The term “ecosystem” is often used very imprecisely and linked with a descriptive term (adjective) even if those systems are rather biomes, not ecosystems.[citation needed] Examples include: terrestrial ecosystem or aquatic ecosystems. Aquatic ecosystems are split into marine ecosystems (Large marine ecosystem is another term used) and freshwater ecosystems.

Ecosystems are controlled both by external and internal factors. External factors, also called state factors, control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem. The most important of these is climate.[9] Climate determines the biome in which the ecosystem is embedded. Rainfall patterns and temperature seasonality determine the amount of water available to the ecosystem and the supply of energy available (by influencing photosynthesis).[9]

Parent material, the underlying geological material that gives rise to soils, determines the nature of the soils present, and influences the supply of mineral nutrients. Topography also controls ecosystem processes by affecting things like microclimate, soil development and the movement of water through a system. This may be the difference between the ecosystem present in wetland situated in a small depression on the landscape, and one present on an adjacent steep hillside.[9]

Other external factors that play an important role in ecosystem functioning include time and potential biota. Similarly, the set of organisms that can potentially be present in an area can also have a major impact on ecosystems. Ecosystems in similar environments that are located in different parts of the world can end up doing things very differently simply because they have different pools of species present.[9] The introduction of non-native species can cause substantial shifts in ecosystem function.

Unlike external factors, internal factors in ecosystems not only control ecosystem processes, but are also controlled by them. Consequently, they are often subject to feedback loops.[9] While the resource inputs are generally controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading.[9] Other factors like disturbance, succession or the types of species present are also internal factors.

Primary production is the production of organic matter from inorganic carbon sources. This mainly occurs through photosynthesis. The energy incorporated through this process supports life on earth, while the carbon makes up much of the organic matter in living and dead biomass, soil carbon and fossil fuels. It also drives the carbon cycle, which influences global climate via the greenhouse effect.

Through the process of photosynthesis, plants capture energy from light and use it to combine carbon dioxide and water to produce carbohydrates and oxygen. The photosynthesis carried out by all the plants in an ecosystem is called the gross primary production (GPP).[17] About 4860% of the GPP is consumed in plant respiration.

The remainder, that portion of GPP that is not used up by respiration, is known as the net primary production (NPP).[18]

Energy and carbon enter ecosystems through photosynthesis, are incorporated into living tissue, transferred to other organisms that feed on the living and dead plant matter, and eventually released through respiration.[18]

The carbon and energy incorporated into plant tissues (net primary production) is either consumed by animals while the plant is alive, or it remains uneaten when the plant tissue dies and becomes detritus. In terrestrial ecosystems, roughly 90% of the net primary production ends up being broken down by decomposers. The remainder is either consumed by animals while still alive and enters the plant-based trophic system, or it is consumed after it has died, and enters the detritus-based trophic system.

In aquatic systems, the proportion of plant biomass that gets consumed by herbivores is much higher.[19] In trophic systems photosynthetic organisms are the primary producers. The organisms that consume their tissues are called primary consumers or secondary producersherbivores. Organisms which feed on microbes (bacteria and fungi) are termed microbivores. Animals that feed on primary consumerscarnivoresare secondary consumers. Each of these constitutes a trophic level.[19]

The sequence of consumptionfrom plant to herbivore, to carnivoreforms a food chain. Real systems are much more complex than thisorganisms will generally feed on more than one form of food, and may feed at more than one trophic level. Carnivores may capture some prey which are part of a plant-based trophic system and others that are part of a detritus-based trophic system (a bird that feeds both on herbivorous grasshoppers and earthworms, which consume detritus). Real systems, with all these complexities, form food webs rather than food chains.[19]

Ecosystem ecology studies “the flow of energy and materials through organisms and the physical environment”. It seeks to understand the processes which govern the stocks of material and energy in ecosystems, and the flow of matter and energy through them. The study of ecosystems can cover 10 orders of magnitude, from the surface layers of rocks to the surface of the planet.[20]

The carbon and nutrients in dead organic matter are broken down by a group of processes known as decomposition. This releases nutrients that can then be re-used for plant and microbial production, and returns carbon dioxide to the atmosphere (or water) where it can be used for photosynthesis. In the absence of decomposition, dead organic matter would accumulate in an ecosystem, and nutrients and atmospheric carbon dioxide would be depleted.[21] Approximately 90% of terrestrial net primary production goes directly from plant to decomposer.[19]

Decomposition processes can be separated into three categoriesleaching, fragmentation and chemical alteration of dead material.

As water moves through dead organic matter, it dissolves and carries with it the water-soluble components. These are then taken up by organisms in the soil, react with mineral soil, or are transported beyond the confines of the ecosystem (and are considered lost to it).[21] Newly shed leaves and newly dead animals have high concentrations of water-soluble components, and include sugars, amino acids and mineral nutrients. Leaching is more important in wet environments, and much less important in dry ones.[21]

Fragmentation processes break organic material into smaller pieces, exposing new surfaces for colonization by microbes. Freshly shed leaf litter may be inaccessible due to an outer layer of cuticle or bark, and cell contents are protected by a cell wall. Newly dead animals may be covered by an exoskeleton. Fragmentation processes, which break through these protective layers, accelerate the rate of microbial decomposition.[21] Animals fragment detritus as they hunt for food, as does passage through the gut. Freeze-thaw cycles and cycles of wetting and drying also fragment dead material.[21]

The chemical alteration of dead organic matter is primarily achieved through bacterial and fungal action. Fungal hyphae produce enzymes which can break through the tough outer structures surrounding dead plant material. They also produce enzymes which break down lignin, which allows them access to both cell contents and to the nitrogen in the lignin. Fungi can transfer carbon and nitrogen through their hyphal networks and thus, unlike bacteria, are not dependent solely on locally available resources.[21]

Decomposition rates vary among ecosystems. The rate of decomposition is governed by three sets of factorsthe physical environment (temperature, moisture and soil properties), the quantity and quality of the dead material available to decomposers, and the nature of the microbial community itself.[22] Temperature controls the rate of microbial respiration; the higher the temperature, the faster microbial decomposition occurs. It also affects soil moisture, which slows microbial growth and reduces leaching. Freeze-thaw cycles also affect decompositionfreezing temperatures kill soil microorganisms, which allows leaching to play a more important role in moving nutrients around. This can be especially important as the soil thaws in the spring, creating a pulse of nutrients which become available.[22]

Decomposition rates are low under very wet or very dry conditions. Decomposition rates are highest in wet, moist conditions with adequate levels of oxygen. Wet soils tend to become deficient in oxygen (this is especially true in wetlands), which slows microbial growth. In dry soils, decomposition slows as well, but bacteria continue to grow (albeit at a slower rate) even after soils become too dry to support plant growth.

Ecosystems continually exchange energy and carbon with the wider environment. Mineral nutrients, on the other hand, are mostly cycled back and forth between plants, animals, microbes and the soil. Most nitrogen enters ecosystems through biological nitrogen fixation, is deposited through precipitation, dust, gases or is applied as fertilizer.[23]

Since most terrestrial ecosystems are nitrogen-limited, nitrogen cycling is an important control on ecosystem production.[23]

Until modern times, nitrogen fixation was the major source of nitrogen for ecosystems. Nitrogen fixing bacteria either live symbiotically with plants, or live freely in the soil. The energetic cost is high for plants which support nitrogen-fixing symbiontsas much as 25% of gross primary production when measured in controlled conditions. Many members of the legume plant family support nitrogen-fixing symbionts. Some cyanobacteria are also capable of nitrogen fixation. These are phototrophs, which carry out photosynthesis. Like other nitrogen-fixing bacteria, they can either be free-living or have symbiotic relationships with plants.[23] Other sources of nitrogen include acid deposition produced through the combustion of fossil fuels, ammonia gas which evaporates from agricultural fields which have had fertilizers applied to them, and dust.[23] Anthropogenic nitrogen inputs account for about 80% of all nitrogen fluxes in ecosystems.[23]

When plant tissues are shed or are eaten, the nitrogen in those tissues becomes available to animals and microbes. Microbial decomposition releases nitrogen compounds from dead organic matter in the soil, where plants, fungi and bacteria compete for it. Some soil bacteria use organic nitrogen-containing compounds as a source of carbon, and release ammonium ions into the soil. This process is known as nitrogen mineralization. Others convert ammonium to nitrite and nitrate ions, a process known as nitrification. Nitric oxide and nitrous oxide are also produced during nitrification.[23] Under nitrogen-rich and oxygen-poor conditions, nitrates and nitrites are converted to nitrogen gas, a process known as denitrification.[23]

Other important nutrients include phosphorus, sulfur, calcium, potassium, magnesium and manganese.[24] Phosphorus enters ecosystems through weathering. As ecosystems age this supply diminishes, making phosphorus-limitation more common in older landscapes (especially in the tropics).[24] Calcium and sulfur are also produced by weathering, but acid deposition is an important source of sulfur in many ecosystems. Although magnesium and manganese are produced by weathering, exchanges between soil organic matter and living cells account for a significant portion of ecosystem fluxes. Potassium is primarily cycled between living cells and soil organic matter.[24]

Biodiversity plays an important role in ecosystem functioning.[26] The reason for this is that ecosystem processes are driven by the number of species in an ecosystem, the exact nature of each individual species, and the relative abundance organisms within these species.[27] Ecosystem processes are broad generalizations that actually take place through the actions of individual organisms. The nature of the organismsthe species, functional groups and trophic levels to which they belongdictates the sorts of actions these individuals are capable of carrying out, and the relative efficiency with which they do so.

Ecological theory suggests that in order to coexist, species must have some level of limiting similaritythey must be different from one another in some fundamental way, otherwise one species would competitively exclude the other.[28] Despite this, the cumulative effect of additional species in an ecosystem is not linearadditional species may enhance nitrogen retention, for example, but beyond some level of species richness, additional species may have little additive effect.[27]

The addition (or loss) of species which are ecologically similar to those already present in an ecosystem tends to only have a small effect on ecosystem function. Ecologically distinct species, on the other hand, have a much larger effect. Similarly, dominant species have a large impact on ecosystem function, while rare species tend to have a small effect. Keystone species tend to have an effect on ecosystem function that is disproportionate to their abundance in an ecosystem.[27] Similarly, an ecosystem engineer is any organism that creates, significantly modifies, maintains or destroys a habitat.

Ecosystems are dynamic entities. They are subject to periodic disturbances and are in the process of recovering from some past disturbance.[10] When a perturbation occurs, an ecoystem responds by moving away from its initial state. The tendency of an ecosystem to remain close to its equilibrium state, despite that disturbance, is termed its resistance. On the other hand, the speed with which it returns to its initial state after disturbance is called its resilience.[10] Time plays a role in the development of soil from bare rock and the recovery of a community from disturbance.[9]

From one year to another, ecosystems experience variation in their biotic and abiotic environments. A drought, an especially cold winter and a pest outbreak all constitute short-term variability in environmental conditions. Animal populations vary from year to year, building up during resource-rich periods and crashing as they overshoot their food supply. These changes play out in changes in net primary production decomposition rates, and other ecosystem processes.[10] Longer-term changes also shape ecosystem processesthe forests of eastern North America still show legacies of cultivation which ceased 200 years ago, while methane production in eastern Siberian lakes is controlled by organic matter which accumulated during the Pleistocene.[10]

Disturbance also plays an important role in ecological processes. F. Stuart Chapin and coauthors define disturbance as “a relatively discrete event in time and space that alters the structure of populations, communities and ecosystems and causes changes in resources availability or the physical environment”.[29] This can range from tree falls and insect outbreaks to hurricanes and wildfires to volcanic eruptions. Such disturbances can cause large changes in plant, animal and microbe populations, as well soil organic matter content.[10] Disturbance is followed by succession, a “directional change in ecosystem structure and functioning resulting from biotically driven changes in resources supply.”[29]

The frequency and severity of disturbance determines the way it impacts ecosystem function. Major disturbance like a volcanic eruption or glacial advance and retreat leave behind soils that lack plants, animals or organic matter. Ecosystems that experience such disturbances undergo primary succession. Less severe disturbance like forest fires, hurricanes or cultivation result in secondary succession and a faster recovery.[10] More severe disturbance and more frequent disturbance result in longer recovery times.

Classifying ecosystems into ecologically homogeneous units is an important step towards effective ecosystem management.[30] There is no single, agreed-upon way to do this. A variety of systems exist, based on vegetation cover, remote sensing, and bioclimatic classification systems.[30]

Ecological land classification is a cartographical delineation or regionalisation of distinct ecological areas, identified by their geology, topography, soils, vegetation, climate conditions, living species, habitats, water resources, and sometimes also anthropic factors.[31]

Human activities are important in almost all ecosystems. Although humans exist and operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.[9]

Ecosystems provide a variety of goods and services upon which people depend.[32] Ecosystem goods include the “tangible, material products” of ecosystem processes such as food, construction material, medicinal plants.[33] They also include less tangible items like tourism and recreation, and genes from wild plants and animals that can be used to improve domestic species.[32]

Ecosystem services, on the other hand, are generally “improvements in the condition or location of things of value”.[33] These include things like the maintenance of hydrological cycles, cleaning air and water, the maintenance of oxygen in the atmosphere, crop pollination and even things like beauty, inspiration and opportunities for research.[32] While ecosystem goods have traditionally been recognized as being the basis for things of economic value, ecosystem services tend to be taken for granted.[33]

When natural resource management is applied to whole ecosystems, rather than single species, it is termed ecosystem management.[34] Although definitions of ecosystem management abound, there is a common set of principles which underlie these definitions.[35] A fundamental principle is the long-term sustainability of the production of goods and services by the ecosystem;[35] “intergenerational sustainability [is] a precondition for management, not an afterthought”.[32]

While ecosystem management can be used as part of a plan for wilderness conservation, it can also be used in intensively managed ecosystems[32] (see, for example, agroecosystem and close to nature forestry).

As human populations and per capita consumption grow, so do the resource demands imposed on ecosystems and the impacts of the human ecological footprint. Natural resources are vulnerable and limited. The environmental impacts of anthropogenic actions are becoming more apparent. Problems for all ecosystems include: environmental pollution, climate change and biodiversity loss. For terrestrial ecosystems further threats include air pollution, soil degradation, and deforestation. For aquatic ecosystems threats include also unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollution, microplastics pollution, water pollution, and building on coastal areas.[36]

Society is increasingly becoming aware that ecosystem services are not only limited, but also that they are threatened by human activities. The need to better consider long-term ecosystem health and its role in enabling human habitation and economic activity is urgent. To help inform decision-makers, many ecosystem services are being assigned economic values, often based on the cost of replacement with anthropogenic alternatives. The ongoing challenge of prescribing economic value to nature, for example through biodiversity banking, is prompting transdisciplinary shifts in how we recognize and manage the environment, social responsibility, business opportunities, and our future as a species.[citation needed]

The term “ecosystem” was first used in 1935 in a publication by British ecologist Arthur Tansley.[fn 1][37] Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment.[38] He later refined the term, describing it as “The whole system, … including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment”.[39] Tansley regarded ecosystems not simply as natural units, but as “mental isolates”.[39] Tansley later defined the spatial extent of ecosystems using the term ecotope.[40]

G. Evelyn Hutchinson, a limnologist who was a contemporary of Tansley’s, combined Charles Elton’s ideas about trophic ecology with those of Russian geochemist Vladimir Vernadsky. As a result he suggested that mineral nutrient availability in a lake limited algal production. This would, in turn, limit the abundance of animals that feed on algae. Raymond Lindeman took these ideas further to suggest that the flow of energy through a lake was the primary driver of the ecosystem. Hutchinson’s students, brothers Howard T. Odum and Eugene P. Odum, further developed a “systems approach” to the study of ecosystems. This allowed them to study the flow of energy and material through ecological systems.[38]

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Ecosystem – Wikipedia

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1 Bitglass Report: Security Concerns Limit Cloud Adoption, Talkin Cloud, March 2014. Published at http://talkincloud.com/cloud-computing-research/050114/bitglass-report-security-concerns-limit-cloud-adoption

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Ecosystem – Wikipedia

This article is about natural ecosystems. For the term used in man-made systems, see Digital ecosystem.

An ecosystem can be defined as a community made up of living organisms and nonliving components such as air, water and mineral soil.[2] However, ecosystems can be defined in many ways.[3] The biotic and abiotic components interact through nutrient cycles and energy flows.[4] Ecosystems include a network of interactions among organisms, and between organisms and their environment.[5] Ecosystems can be of any size but one ecosystem has a specific, limited space.[6] Some scientists view the entire planet as one ecosystem.[7]

Energy, water, nitrogen and soil minerals are other essential abiotic components of an ecosystem. The energy that flows through ecosystems comes primarily from the sun, through photosynthesis. Photosynthesis also captures carbon dioxide from the atmosphere. Animals also play an important role in the movement of matter and energy through ecoystems. They influence the amount of plant and microbial biomass that lives in the system. As organic matter dies, decomposers release carbon back to the atmosphere. This process also facilitates nutrient cycling by converting nutrients stored in dead biomass back to a form that can be used again by plants and other microbes.[8]

Ecosystems are controlled both by external and internal factors. External factors such as climate, the parent material that forms the soil, topography and time have a big impact on ecosystems, but they are not themselves influenced by the ecosystem.[9] Ecosystems are dynamic: they are subject to periodic disturbances and are in the process of recovering from past disturbances.[10] Internal factors are different: They not only control ecosystem processes but are also controlled by them. Internal factors are subject to feedback loops.[9]

Humans operate within ecosystems. The effects of human activities can influence internal and external factors.[9] Global warming is an example of a cumulative impact of human activities. Ecosystems provide benefits, called “ecosystem services”, which people depend on for their livelihood. Ecosystem management is more efficient than trying to manage individual species.

There is no single definition of what constitutes an ecosystem.[3] German ecologist Ernst-Detlef Schulze and coauthors defined an ecosystem as an area which is “uniform regarding the biological turnover, and contains all the fluxes above and below the ground area under consideration.” They explicitly reject Gene Likens’ use of entire river catchments as “too wide a demarcation” to be a single ecosystem, given the level of heterogeneity within such an area.[11] Other authors have suggested that an ecosystem can encompass a much larger area, even the whole planet.[7] Schulze and coauthors also rejected the idea that a single rotting log could be studied as an ecosystem because the size of the flows between the log and its surroundings are too large, relative to the proportion cycles within the log.[11] Philosopher of science Mark Sagoff considers the failure to define “the kind of object it studies” to be an obstacle to the development of theory in ecosystem ecology.[3]

Ecosystems can be studied through a variety of approachestheoretical studies, studies monitoring specific ecosystems over long periods of time, those that look at differences between ecosystems to elucidate how they work and direct manipulative experimentation.[12] Studies can be carried out at a variety of scales, from microcosms and mesocosms which serve as simplified representations of ecosystems, through whole-ecosystem studies.[13] American ecologist Stephen R. Carpenter has argued that microcosm experiments can be “irrelevant and diversionary” if they are not carried out in conjunction with field studies carried out at the ecosystem scale, because microcosm experiments often fail to accurately predict ecosystem-level dynamics.[14]

The Hubbard Brook Ecosystem Study, established in the White Mountains, New Hampshire in 1963, was the first successful attempt to study an entire watershed as an ecosystem. The study used stream chemistry as a means of monitoring ecosystem properties, and developed a detailed biogeochemical model of the ecosystem.[15] Long-term research at the site led to the discovery of acid rain in North America in 1972, and was able to document the consequent depletion of soil cations (especially calcium) over the next several decades.[16]

The term “ecosystem” is often used very imprecisely and linked with a descriptive term (adjective) even if those systems are rather biomes, not ecosystems.[citation needed] Examples include: terrestrial ecosystem or aquatic ecosystems. Aquatic ecosystems are split into marine ecosystems (Large marine ecosystem is another term used) and freshwater ecosystems.

Ecosystems are controlled both by external and internal factors. External factors, also called state factors, control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem. The most important of these is climate.[9] Climate determines the biome in which the ecosystem is embedded. Rainfall patterns and temperature seasonality determine the amount of water available to the ecosystem and the supply of energy available (by influencing photosynthesis).[9]

Parent material, the underlying geological material that gives rise to soils, determines the nature of the soils present, and influences the supply of mineral nutrients. Topography also controls ecosystem processes by affecting things like microclimate, soil development and the movement of water through a system. This may be the difference between the ecosystem present in wetland situated in a small depression on the landscape, and one present on an adjacent steep hillside.[9]

Other external factors that play an important role in ecosystem functioning include time and potential biota. Similarly, the set of organisms that can potentially be present in an area can also have a major impact on ecosystems. Ecosystems in similar environments that are located in different parts of the world can end up doing things very differently simply because they have different pools of species present.[9] The introduction of non-native species can cause substantial shifts in ecosystem function.

Unlike external factors, internal factors in ecosystems not only control ecosystem processes, but are also controlled by them. Consequently, they are often subject to feedback loops.[9] While the resource inputs are generally controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading.[9] Other factors like disturbance, succession or the types of species present are also internal factors.

Primary production is the production of organic matter from inorganic carbon sources. This mainly occurs through photosynthesis. The energy incorporated through this process supports life on earth, while the carbon makes up much of the organic matter in living and dead biomass, soil carbon and fossil fuels. It also drives the carbon cycle, which influences global climate via the greenhouse effect.

Through the process of photosynthesis, plants capture energy from light and use it to combine carbon dioxide and water to produce carbohydrates and oxygen. The photosynthesis carried out by all the plants in an ecosystem is called the gross primary production (GPP).[17] About 4860% of the GPP is consumed in plant respiration.

The remainder, that portion of GPP that is not used up by respiration, is known as the net primary production (NPP).[18]

Energy and carbon enter ecosystems through photosynthesis, are incorporated into living tissue, transferred to other organisms that feed on the living and dead plant matter, and eventually released through respiration.[18]

The carbon and energy incorporated into plant tissues (net primary production) is either consumed by animals while the plant is alive, or it remains uneaten when the plant tissue dies and becomes detritus. In terrestrial ecosystems, roughly 90% of the net primary production ends up being broken down by decomposers. The remainder is either consumed by animals while still alive and enters the plant-based trophic system, or it is consumed after it has died, and enters the detritus-based trophic system.

In aquatic systems, the proportion of plant biomass that gets consumed by herbivores is much higher.[19] In trophic systems photosynthetic organisms are the primary producers. The organisms that consume their tissues are called primary consumers or secondary producersherbivores. Organisms which feed on microbes (bacteria and fungi) are termed microbivores. Animals that feed on primary consumerscarnivoresare secondary consumers. Each of these constitutes a trophic level.[19]

The sequence of consumptionfrom plant to herbivore, to carnivoreforms a food chain. Real systems are much more complex than thisorganisms will generally feed on more than one form of food, and may feed at more than one trophic level. Carnivores may capture some prey which are part of a plant-based trophic system and others that are part of a detritus-based trophic system (a bird that feeds both on herbivorous grasshoppers and earthworms, which consume detritus). Real systems, with all these complexities, form food webs rather than food chains.[19]

Ecosystem ecology studies “the flow of energy and materials through organisms and the physical environment”. It seeks to understand the processes which govern the stocks of material and energy in ecosystems, and the flow of matter and energy through them. The study of ecosystems can cover 10 orders of magnitude, from the surface layers of rocks to the surface of the planet.[20]

The carbon and nutrients in dead organic matter are broken down by a group of processes known as decomposition. This releases nutrients that can then be re-used for plant and microbial production, and returns carbon dioxide to the atmosphere (or water) where it can be used for photosynthesis. In the absence of decomposition, dead organic matter would accumulate in an ecosystem, and nutrients and atmospheric carbon dioxide would be depleted.[21] Approximately 90% of terrestrial net primary production goes directly from plant to decomposer.[19]

Decomposition processes can be separated into three categoriesleaching, fragmentation and chemical alteration of dead material.

As water moves through dead organic matter, it dissolves and carries with it the water-soluble components. These are then taken up by organisms in the soil, react with mineral soil, or are transported beyond the confines of the ecosystem (and are considered lost to it).[21] Newly shed leaves and newly dead animals have high concentrations of water-soluble components, and include sugars, amino acids and mineral nutrients. Leaching is more important in wet environments, and much less important in dry ones.[21]

Fragmentation processes break organic material into smaller pieces, exposing new surfaces for colonization by microbes. Freshly shed leaf litter may be inaccessible due to an outer layer of cuticle or bark, and cell contents are protected by a cell wall. Newly dead animals may be covered by an exoskeleton. Fragmentation processes, which break through these protective layers, accelerate the rate of microbial decomposition.[21] Animals fragment detritus as they hunt for food, as does passage through the gut. Freeze-thaw cycles and cycles of wetting and drying also fragment dead material.[21]

The chemical alteration of dead organic matter is primarily achieved through bacterial and fungal action. Fungal hyphae produce enzymes which can break through the tough outer structures surrounding dead plant material. They also produce enzymes which break down lignin, which allows them access to both cell contents and to the nitrogen in the lignin. Fungi can transfer carbon and nitrogen through their hyphal networks and thus, unlike bacteria, are not dependent solely on locally available resources.[21]

Decomposition rates vary among ecosystems. The rate of decomposition is governed by three sets of factorsthe physical environment (temperature, moisture and soil properties), the quantity and quality of the dead material available to decomposers, and the nature of the microbial community itself.[22] Temperature controls the rate of microbial respiration; the higher the temperature, the faster microbial decomposition occurs. It also affects soil moisture, which slows microbial growth and reduces leaching. Freeze-thaw cycles also affect decompositionfreezing temperatures kill soil microorganisms, which allows leaching to play a more important role in moving nutrients around. This can be especially important as the soil thaws in the spring, creating a pulse of nutrients which become available.[22]

Decomposition rates are low under very wet or very dry conditions. Decomposition rates are highest in wet, moist conditions with adequate levels of oxygen. Wet soils tend to become deficient in oxygen (this is especially true in wetlands), which slows microbial growth. In dry soils, decomposition slows as well, but bacteria continue to grow (albeit at a slower rate) even after soils become too dry to support plant growth.

Ecosystems continually exchange energy and carbon with the wider environment. Mineral nutrients, on the other hand, are mostly cycled back and forth between plants, animals, microbes and the soil. Most nitrogen enters ecosystems through biological nitrogen fixation, is deposited through precipitation, dust, gases or is applied as fertilizer.[23]

Since most terrestrial ecosystems are nitrogen-limited, nitrogen cycling is an important control on ecosystem production.[23]

Until modern times, nitrogen fixation was the major source of nitrogen for ecosystems. Nitrogen fixing bacteria either live symbiotically with plants, or live freely in the soil. The energetic cost is high for plants which support nitrogen-fixing symbiontsas much as 25% of gross primary production when measured in controlled conditions. Many members of the legume plant family support nitrogen-fixing symbionts. Some cyanobacteria are also capable of nitrogen fixation. These are phototrophs, which carry out photosynthesis. Like other nitrogen-fixing bacteria, they can either be free-living or have symbiotic relationships with plants.[23] Other sources of nitrogen include acid deposition produced through the combustion of fossil fuels, ammonia gas which evaporates from agricultural fields which have had fertilizers applied to them, and dust.[23] Anthropogenic nitrogen inputs account for about 80% of all nitrogen fluxes in ecosystems.[23]

When plant tissues are shed or are eaten, the nitrogen in those tissues becomes available to animals and microbes. Microbial decomposition releases nitrogen compounds from dead organic matter in the soil, where plants, fungi and bacteria compete for it. Some soil bacteria use organic nitrogen-containing compounds as a source of carbon, and release ammonium ions into the soil. This process is known as nitrogen mineralization. Others convert ammonium to nitrite and nitrate ions, a process known as nitrification. Nitric oxide and nitrous oxide are also produced during nitrification.[23] Under nitrogen-rich and oxygen-poor conditions, nitrates and nitrites are converted to nitrogen gas, a process known as denitrification.[23]

Other important nutrients include phosphorus, sulfur, calcium, potassium, magnesium and manganese.[24] Phosphorus enters ecosystems through weathering. As ecosystems age this supply diminishes, making phosphorus-limitation more common in older landscapes (especially in the tropics).[24] Calcium and sulfur are also produced by weathering, but acid deposition is an important source of sulfur in many ecosystems. Although magnesium and manganese are produced by weathering, exchanges between soil organic matter and living cells account for a significant portion of ecosystem fluxes. Potassium is primarily cycled between living cells and soil organic matter.[24]

Biodiversity plays an important role in ecosystem functioning.[26] The reason for this is that ecosystem processes are driven by the number of species in an ecosystem, the exact nature of each individual species, and the relative abundance organisms within these species.[27] Ecosystem processes are broad generalizations that actually take place through the actions of individual organisms. The nature of the organismsthe species, functional groups and trophic levels to which they belongdictates the sorts of actions these individuals are capable of carrying out, and the relative efficiency with which they do so.

Ecological theory suggests that in order to coexist, species must have some level of limiting similaritythey must be different from one another in some fundamental way, otherwise one species would competitively exclude the other.[28] Despite this, the cumulative effect of additional species in an ecosystem is not linearadditional species may enhance nitrogen retention, for example, but beyond some level of species richness, additional species may have little additive effect.[27]

The addition (or loss) of species which are ecologically similar to those already present in an ecosystem tends to only have a small effect on ecosystem function. Ecologically distinct species, on the other hand, have a much larger effect. Similarly, dominant species have a large impact on ecosystem function, while rare species tend to have a small effect. Keystone species tend to have an effect on ecosystem function that is disproportionate to their abundance in an ecosystem.[27] Similarly, an ecosystem engineer is any organism that creates, significantly modifies, maintains or destroys a habitat.

Ecosystems are dynamic entities. They are subject to periodic disturbances and are in the process of recovering from some past disturbance.[10] When a perturbation occurs, an ecoystem responds by moving away from its initial state. The tendency of an ecosystem to remain close to its equilibrium state, despite that disturbance, is termed its resistance. On the other hand, the speed with which it returns to its initial state after disturbance is called its resilience.[10] Time plays a role in the development of soil from bare rock and the recovery of a community from disturbance.[9]

From one year to another, ecosystems experience variation in their biotic and abiotic environments. A drought, an especially cold winter and a pest outbreak all constitute short-term variability in environmental conditions. Animal populations vary from year to year, building up during resource-rich periods and crashing as they overshoot their food supply. These changes play out in changes in net primary production decomposition rates, and other ecosystem processes.[10] Longer-term changes also shape ecosystem processesthe forests of eastern North America still show legacies of cultivation which ceased 200 years ago, while methane production in eastern Siberian lakes is controlled by organic matter which accumulated during the Pleistocene.[10]

Disturbance also plays an important role in ecological processes. F. Stuart Chapin and coauthors define disturbance as “a relatively discrete event in time and space that alters the structure of populations, communities and ecosystems and causes changes in resources availability or the physical environment”.[29] This can range from tree falls and insect outbreaks to hurricanes and wildfires to volcanic eruptions. Such disturbances can cause large changes in plant, animal and microbe populations, as well soil organic matter content.[10] Disturbance is followed by succession, a “directional change in ecosystem structure and functioning resulting from biotically driven changes in resources supply.”[29]

The frequency and severity of disturbance determines the way it impacts ecosystem function. Major disturbance like a volcanic eruption or glacial advance and retreat leave behind soils that lack plants, animals or organic matter. Ecosystems that experience such disturbances undergo primary succession. Less severe disturbance like forest fires, hurricanes or cultivation result in secondary succession and a faster recovery.[10] More severe disturbance and more frequent disturbance result in longer recovery times.

Classifying ecosystems into ecologically homogeneous units is an important step towards effective ecosystem management.[30] There is no single, agreed-upon way to do this. A variety of systems exist, based on vegetation cover, remote sensing, and bioclimatic classification systems.[30]

Ecological land classification is a cartographical delineation or regionalisation of distinct ecological areas, identified by their geology, topography, soils, vegetation, climate conditions, living species, habitats, water resources, and sometimes also anthropic factors.[31]

Human activities are important in almost all ecosystems. Although humans exist and operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.[9]

Ecosystems provide a variety of goods and services upon which people depend.[32] Ecosystem goods include the “tangible, material products” of ecosystem processes such as food, construction material, medicinal plants.[33] They also include less tangible items like tourism and recreation, and genes from wild plants and animals that can be used to improve domestic species.[32]

Ecosystem services, on the other hand, are generally “improvements in the condition or location of things of value”.[33] These include things like the maintenance of hydrological cycles, cleaning air and water, the maintenance of oxygen in the atmosphere, crop pollination and even things like beauty, inspiration and opportunities for research.[32] While ecosystem goods have traditionally been recognized as being the basis for things of economic value, ecosystem services tend to be taken for granted.[33]

When natural resource management is applied to whole ecosystems, rather than single species, it is termed ecosystem management.[34] Although definitions of ecosystem management abound, there is a common set of principles which underlie these definitions.[35] A fundamental principle is the long-term sustainability of the production of goods and services by the ecosystem;[35] “intergenerational sustainability [is] a precondition for management, not an afterthought”.[32]

While ecosystem management can be used as part of a plan for wilderness conservation, it can also be used in intensively managed ecosystems[32] (see, for example, agroecosystem and close to nature forestry).

As human populations and per capita consumption grow, so do the resource demands imposed on ecosystems and the impacts of the human ecological footprint. Natural resources are vulnerable and limited. The environmental impacts of anthropogenic actions are becoming more apparent. Problems for all ecosystems include: environmental pollution, climate change and biodiversity loss. For terrestrial ecosystems further threats include air pollution, soil degradation, and deforestation. For aquatic ecosystems threats include also unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollution, microplastics pollution, water pollution, and building on coastal areas.[36]

Society is increasingly becoming aware that ecosystem services are not only limited, but also that they are threatened by human activities. The need to better consider long-term ecosystem health and its role in enabling human habitation and economic activity is urgent. To help inform decision-makers, many ecosystem services are being assigned economic values, often based on the cost of replacement with anthropogenic alternatives. The ongoing challenge of prescribing economic value to nature, for example through biodiversity banking, is prompting transdisciplinary shifts in how we recognize and manage the environment, social responsibility, business opportunities, and our future as a species.[citation needed]

The term “ecosystem” was first used in 1935 in a publication by British ecologist Arthur Tansley.[fn 1][37] Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment.[38] He later refined the term, describing it as “The whole system, … including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment”.[39] Tansley regarded ecosystems not simply as natural units, but as “mental isolates”.[39] Tansley later defined the spatial extent of ecosystems using the term ecotope.[40]

G. Evelyn Hutchinson, a limnologist who was a contemporary of Tansley’s, combined Charles Elton’s ideas about trophic ecology with those of Russian geochemist Vladimir Vernadsky. As a result he suggested that mineral nutrient availability in a lake limited algal production. This would, in turn, limit the abundance of animals that feed on algae. Raymond Lindeman took these ideas further to suggest that the flow of energy through a lake was the primary driver of the ecosystem. Hutchinson’s students, brothers Howard T. Odum and Eugene P. Odum, further developed a “systems approach” to the study of ecosystems. This allowed them to study the flow of energy and material through ecological systems.[38]

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Ecosystem – Wikipedia

Ecosystem – Wikipedia

This article is about natural ecosystems. For the term used in man-made systems, see Digital ecosystem.

An ecosystem is a community made up of living organisms and nonliving components such as air, water and mineral soil, all interacting as a system.[2] (However, ecosystems can be defined in many ways.[3]) The biotic and abiotic components interact through nutrient cycles and energy flows.[4] Ecosystems are the network of interactions among organisms, and between organisms and their environment.[5] Ecosystems can be of any size but one ecosystem has a specific, limited space.[6] On a larger scale, some scientists view the entire planet as one ecosystem).[7]

Energy, water, nitrogen and soil minerals are other essential abiotic components of an ecosystem. The energy that flows through ecosystems comes primarily from the sun, through photosynthesis. Photosynthesis also captures carbon dioxide from the atmosphere. Animals also play an important role in the movement of matter and energy through ecoystems. They influence the amount plant and microbial biomass that lives in the system. As organic matter dies, decomposers release carbon back to the atmosphere. This process also facilitates nutrient cycling by converting nutrients stored in dead biomass back to a form that can be used again by plants and other microbes.[8]

Ecosystems are controlled both by external and internal factors. External factors such as climate, the parent material that forms the soil, topography and time have a big impact on ecosystems, but they are not themselves influenced by the ecosystem.[9] Ecosystems are dynamic: they are subject to periodic disturbances and are in the process of recovering from past disturbances that were external to the ecosystem.[10] Internal factors are different. They not only control ecosystem processes but are also controlled by them. Internal factors are subject to feedback loops.[9]

Humans operate within ecosystems and the cumulative effects of human activities can influence even external factors.[9] Climate change is an example of that cumulative impact. Ecosystems provide benefits–called Ecosystem services–which people depend on and can disrupt to their own detriment. Best practices of Ecosystem management suggests that it’s better to manage at the ecosystem level, rather than trying to managing individual species.

There is no single definition of what constitutes an ecosystem.[3] German ecologist Ernst-Detlef Schulze and coauthors defined an ecosystem as an area which is “uniform regarding the biological turnover, and contains all the fluxes above and below the ground area under consideration.” They explicitly reject Gene Likens’ use of entire river catchments as “too wide a demarcation” to be a single ecosystem, given the level of heterogeneity within such an area.[11] Other authors have suggested that an ecosystem can encompass a much larger area, even the whole planet.[7] Schulze and coauthors also rejected the idea that a single rotting log could be studied as an ecosystem because the size of the flows between the log and its surroundings are too large, relative to the proportion cycles within the log.[11] Philosopher of science Mark Sagoff considers the failure to define “the kind of object it studies” to be an obstacle to the development of theory in ecosystem ecology.[3]

Ecosystems can be studied through a variety of approachestheoretical studies, studies monitoring specific ecosystems over long periods of time, those that look at differences between ecosystems to elucidate how they work and direct manipulative experimentation.[12] Studies can be carried out at a variety of scales, from microcosms and mesocosms which serve as simplified representations of ecosystems, through whole-ecosystem studies.[13] American ecologist Stephen R. Carpenter has argued that microcosm experiments can be “irrelevant and diversionary” if they are not carried out in conjunction with field studies carried out at the ecosystem scale, because microcosm experiments often fail to accurately predict ecosystem-level dynamics.[14]

The Hubbard Brook Ecosystem Study, established in the White Mountains, New Hampshire in 1963, was the first successful attempt to study an entire watershed as an ecosystem. The study used stream chemistry as a means of monitoring ecosystem properties, and developed a detailed biogeochemical model of the ecosystem.[15] Long-term research at the site led to the discovery of acid rain in North America in 1972, and was able to document the consequent depletion of soil cations (especially calcium) over the next several decades.[16]

The term “ecosystem” is often used very imprecisely and linked with a descriptive term (adjective) even if those systems are rather biomes, not ecosystems.[citation needed] Examples include: terrestrial ecosystem or aquatic ecosystems. Aquatic ecosystems are split into marine ecosystems (Large marine ecosystem is another term used) and freshwater ecosystems.

Ecosystems are controlled both by external and internal factors. External factors, also called state factors, control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem. The most important of these is climate.[9] Climate determines the biome in which the ecosystem is embedded. Rainfall patterns and temperature seasonality determine the amount of water available to the ecosystem and the supply of energy available (by influencing photosynthesis).[9]

Parent material, the underlying geological material that gives rise to soils, determines the nature of the soils present, and influences the supply of mineral nutrients. Topography also controls ecosystem processes by affecting things like microclimate, soil development and the movement of water through a system. This may be the difference between the ecosystem present in wetland situated in a small depression on the landscape, and one present on an adjacent steep hillside.[9]

Other external factors that play an important role in ecosystem functioning include time and potential biota. Similarly, the set of organisms that can potentially be present in an area can also have a major impact on ecosystems. Ecosystems in similar environments that are located in different parts of the world can end up doing things very differently simply because they have different pools of species present.[9] The introduction of non-native species can cause substantial shifts in ecosystem function.

Unlike external factors, internal factors in ecosystems not only control ecosystem processes, but are also controlled by them. Consequently, they are often subject to feedback loops.[9] While the resource inputs are generally controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading.[9] Other factors like disturbance, succession or the types of species present are also internal factors.

Primary production is the production of organic matter from inorganic carbon sources. This mainly occurs through photosynthesis. The energy incorporated through this process supports life on earth, while the carbon makes up much of the organic matter in living and dead biomass, soil carbon and fossil fuels. It also drives the carbon cycle, which influences global climate via the greenhouse effect.

Through the process of photosynthesis, plants capture energy from light and use it to combine carbon dioxide and water to produce carbohydrates and oxygen. The photosynthesis carried out by all the plants in an ecosystem is called the gross primary production (GPP).[17] About 4860% of the GPP is consumed in plant respiration.

The remainder, that portion of GPP that is not used up by respiration, is known as the net primary production (NPP).[18]

Energy and carbon enter ecosystems through photosynthesis, are incorporated into living tissue, transferred to other organisms that feed on the living and dead plant matter, and eventually released through respiration.[18]

The carbon and energy incorporated into plant tissues (net primary production) is either consumed by animals while the plant is alive, or it remains uneaten when the plant tissue dies and becomes detritus. In terrestrial ecosystems, roughly 90% of the net primary production ends up being broken down by decomposers. The remainder is either consumed by animals while still alive and enters the plant-based trophic system, or it is consumed after it has died, and enters the detritus-based trophic system.

In aquatic systems, the proportion of plant biomass that gets consumed by herbivores is much higher.[19] In trophic systems photosynthetic organisms are the primary producers. The organisms that consume their tissues are called primary consumers or secondary producersherbivores. Organisms which feed on microbes (bacteria and fungi) are termed microbivores. Animals that feed on primary consumerscarnivoresare secondary consumers. Each of these constitutes a trophic level.[19]

The sequence of consumptionfrom plant to herbivore, to carnivoreforms a food chain. Real systems are much more complex than thisorganisms will generally feed on more than one form of food, and may feed at more than one trophic level. Carnivores may capture some prey which are part of a plant-based trophic system and others that are part of a detritus-based trophic system (a bird that feeds both on herbivorous grasshoppers and earthworms, which consume detritus). Real systems, with all these complexities, form food webs rather than food chains.[19]

Ecosystem ecology studies “the flow of energy and materials through organisms and the physical environment”. It seeks to understand the processes which govern the stocks of material and energy in ecosystems, and the flow of matter and energy through them. The study of ecosystems can cover 10 orders of magnitude, from the surface layers of rocks to the surface of the planet.[20]

The carbon and nutrients in dead organic matter are broken down by a group of processes known as decomposition. This releases nutrients that can then be re-used for plant and microbial production, and returns carbon dioxide to the atmosphere (or water) where it can be used for photosynthesis. In the absence of decomposition, dead organic matter would accumulate in an ecosystem, and nutrients and atmospheric carbon dioxide would be depleted.[21] Approximately 90% of terrestrial net primary production goes directly from plant to decomposer.[19]

Decomposition processes can be separated into three categoriesleaching, fragmentation and chemical alteration of dead material.

As water moves through dead organic matter, it dissolves and carries with it the water-soluble components. These are then taken up by organisms in the soil, react with mineral soil, or are transported beyond the confines of the ecosystem (and are considered lost to it).[21] Newly shed leaves and newly dead animals have high concentrations of water-soluble components, and include sugars, amino acids and mineral nutrients. Leaching is more important in wet environments, and much less important in dry ones.[21]

Fragmentation processes break organic material into smaller pieces, exposing new surfaces for colonization by microbes. Freshly shed leaf litter may be inaccessible due to an outer layer of cuticle or bark, and cell contents are protected by a cell wall. Newly dead animals may be covered by an exoskeleton. Fragmentation processes, which break through these protective layers, accelerate the rate of microbial decomposition.[21] Animals fragment detritus as they hunt for food, as does passage through the gut. Freeze-thaw cycles and cycles of wetting and drying also fragment dead material.[21]

The chemical alteration of dead organic matter is primarily achieved through bacterial and fungal action. Fungal hyphae produce enzymes which can break through the tough outer structures surrounding dead plant material. They also produce enzymes which break down lignin, which allows them access to both cell contents and to the nitrogen in the lignin. Fungi can transfer carbon and nitrogen through their hyphal networks and thus, unlike bacteria, are not dependent solely on locally available resources.[21]

Decomposition rates vary among ecosystems. The rate of decomposition is governed by three sets of factorsthe physical environment (temperature, moisture and soil properties), the quantity and quality of the dead material available to decomposers, and the nature of the microbial community itself.[22] Temperature controls the rate of microbial respiration; the higher the temperature, the faster microbial decomposition occurs. It also affects soil moisture, which slows microbial growth and reduces leaching. Freeze-thaw cycles also affect decompositionfreezing temperatures kill soil microorganisms, which allows leaching to play a more important role in moving nutrients around. This can be especially important as the soil thaws in the spring, creating a pulse of nutrients which become available.[22]

Decomposition rates are low under very wet or very dry conditions. Decomposition rates are highest in wet, moist conditions with adequate levels of oxygen. Wet soils tend to become deficient in oxygen (this is especially true in wetlands), which slows microbial growth. In dry soils, decomposition slows as well, but bacteria continue to grow (albeit at a slower rate) even after soils become too dry to support plant growth.

Ecosystems continually exchange energy and carbon with the wider environment. Mineral nutrients, on the other hand, are mostly cycled back and forth between plants, animals, microbes and the soil. Most nitrogen enters ecosystems through biological nitrogen fixation, is deposited through precipitation, dust, gases or is applied as fertilizer.[23]

Since most terrestrial ecosystems are nitrogen-limited, nitrogen cycling is an important control on ecosystem production.[23]

Until modern times, nitrogen fixation was the major source of nitrogen for ecosystems. Nitrogen fixing bacteria either live symbiotically with plants, or live freely in the soil. The energetic cost is high for plants which support nitrogen-fixing symbiontsas much as 25% of gross primary production when measured in controlled conditions. Many members of the legume plant family support nitrogen-fixing symbionts. Some cyanobacteria are also capable of nitrogen fixation. These are phototrophs, which carry out photosynthesis. Like other nitrogen-fixing bacteria, they can either be free-living or have symbiotic relationships with plants.[23] Other sources of nitrogen include acid deposition produced through the combustion of fossil fuels, ammonia gas which evaporates from agricultural fields which have had fertilizers applied to them, and dust.[23] Anthropogenic nitrogen inputs account for about 80% of all nitrogen fluxes in ecosystems.[23]

When plant tissues are shed or are eaten, the nitrogen in those tissues becomes available to animals and microbes. Microbial decomposition releases nitrogen compounds from dead organic matter in the soil, where plants, fungi and bacteria compete for it. Some soil bacteria use organic nitrogen-containing compounds as a source of carbon, and release ammonium ions into the soil. This process is known as nitrogen mineralization. Others convert ammonium to nitrite and nitrate ions, a process known as nitrification. Nitric oxide and nitrous oxide are also produced during nitrification.[23] Under nitrogen-rich and oxygen-poor conditions, nitrates and nitrites are converted to nitrogen gas, a process known as denitrification.[23]

Other important nutrients include phosphorus, sulfur, calcium, potassium, magnesium and manganese.[24] Phosphorus enters ecosystems through weathering. As ecosystems age this supply diminishes, making phosphorus-limitation more common in older landscapes (especially in the tropics).[24] Calcium and sulfur are also produced by weathering, but acid deposition is an important source of sulfur in many ecosystems. Although magnesium and manganese are produced by weathering, exchanges between soil organic matter and living cells account for a significant portion of ecosystem fluxes. Potassium is primarily cycled between living cells and soil organic matter.[24]

Biodiversity plays an important role in ecosystem functioning.[26] The reason for this is that ecosystem processes are driven by the number of species in an ecosystem, the exact nature of each individual species, and the relative abundance organisms within these species.[27] Ecosystem processes are broad generalizations that actually take place through the actions of individual organisms. The nature of the organismsthe species, functional groups and trophic levels to which they belongdictates the sorts of actions these individuals are capable of carrying out, and the relative efficiency with which they do so.

Ecological theory suggests that in order to coexist, species must have some level of limiting similaritythey must be different from one another in some fundamental way, otherwise one species would competitively exclude the other.[28] Despite this, the cumulative effect of additional species in an ecosystem is not linearadditional species may enhance nitrogen retention, for example, but beyond some level of species richness, additional species may have little additive effect.[27]

The addition (or loss) of species which are ecologically similar to those already present in an ecosystem tends to only have a small effect on ecosystem function. Ecologically distinct species, on the other hand, have a much larger effect. Similarly, dominant species have a large impact on ecosystem function, while rare species tend to have a small effect. Keystone species tend to have an effect on ecosystem function that is disproportionate to their abundance in an ecosystem.[27] Similarly, an ecosystem engineer is any organism that creates, significantly modifies, maintains or destroys a habitat.

Ecosystems are dynamic entities. They are subject to periodic disturbances and are in the process of recovering from some past disturbance.[10] When a perturbation occurs, an ecoystem responds by moving away from its initial state. The tendency of an ecosystem to remain close to its equilibrium state, despite that disturbance, is termed its resistance. On the other hand, the speed with which it returns to its initial state after disturbance is called its resilience.[10] Time plays a role in the development of soil from bare rock and the recovery of a community from disturbance.[9]

From one year to another, ecosystems experience variation in their biotic and abiotic environments. A drought, an especially cold winter and a pest outbreak all constitute short-term variability in environmental conditions. Animal populations vary from year to year, building up during resource-rich periods and crashing as they overshoot their food supply. These changes play out in changes in net primary production decomposition rates, and other ecosystem processes.[10] Longer-term changes also shape ecosystem processesthe forests of eastern North America still show legacies of cultivation which ceased 200 years ago, while methane production in eastern Siberian lakes is controlled by organic matter which accumulated during the Pleistocene.[10]

Disturbance also plays an important role in ecological processes. F. Stuart Chapin and coauthors define disturbance as “a relatively discrete event in time and space that alters the structure of populations, communities and ecosystems and causes changes in resources availability or the physical environment”.[29] This can range from tree falls and insect outbreaks to hurricanes and wildfires to volcanic eruptions. Such disturbances can cause large changes in plant, animal and microbe populations, as well soil organic matter content.[10] Disturbance is followed by succession, a “directional change in ecosystem structure and functioning resulting from biotically driven changes in resources supply.”[29]

The frequency and severity of disturbance determines the way it impacts ecosystem function. Major disturbance like a volcanic eruption or glacial advance and retreat leave behind soils that lack plants, animals or organic matter. Ecosystems that experience such disturbances undergo primary succession. Less severe disturbance like forest fires, hurricanes or cultivation result in secondary succession and a faster recovery.[10] More severe disturbance and more frequent disturbance result in longer recovery times.

Classifying ecosystems into ecologically homogeneous units is an important step towards effective ecosystem management.[30] There is no single, agreed-upon way to do this. A variety of systems exist, based on vegetation cover, remote sensing, and bioclimatic classification systems.[30]

Ecological land classification is a cartographical delineation or regionalisation of distinct ecological areas, identified by their geology, topography, soils, vegetation, climate conditions, living species, habitats, water resources, and sometimes also anthropic factors.[31]

Human activities are important in almost all ecosystems. Although humans exist and operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.[9]

Ecosystems provide a variety of goods and services upon which people depend.[32] Ecosystem goods include the “tangible, material products” of ecosystem processes such as food, construction material, medicinal plants.[33] They also include less tangible items like tourism and recreation, and genes from wild plants and animals that can be used to improve domestic species.[32]

Ecosystem services, on the other hand, are generally “improvements in the condition or location of things of value”.[33] These include things like the maintenance of hydrological cycles, cleaning air and water, the maintenance of oxygen in the atmosphere, crop pollination and even things like beauty, inspiration and opportunities for research.[32] While ecosystem goods have traditionally been recognized as being the basis for things of economic value, ecosystem services tend to be taken for granted.[33]

When natural resource management is applied to whole ecosystems, rather than single species, it is termed ecosystem management.[34] Although definitions of ecosystem management abound, there is a common set of principles which underlie these definitions.[35] A fundamental principle is the long-term sustainability of the production of goods and services by the ecosystem;[35] “intergenerational sustainability [is] a precondition for management, not an afterthought”.[32]

While ecosystem management can be used as part of a plan for wilderness conservation, it can also be used in intensively managed ecosystems[32] (see, for example, agroecosystem and close to nature forestry).

As human populations and per capita consumption grow, so do the resource demands imposed on ecosystems and the impacts of the human ecological footprint. Natural resources are vulnerable and limited. The environmental impacts of anthropogenic actions are becoming more apparent. Problems for all ecosystems include: environmental pollution, climate change and biodiversity loss. For terrestrial ecosystems further threats include air pollution, soil degradation, and deforestation. For aquatic ecosystems threats include also unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollution, microplastics pollution, water pollution, and building on coastal areas.[36]

Society is increasingly becoming aware that ecosystem services are not only limited, but also that they are threatened by human activities. The need to better consider long-term ecosystem health and its role in enabling human habitation and economic activity is urgent. To help inform decision-makers, many ecosystem services are being assigned economic values, often based on the cost of replacement with anthropogenic alternatives. The ongoing challenge of prescribing economic value to nature, for example through biodiversity banking, is prompting transdisciplinary shifts in how we recognize and manage the environment, social responsibility, business opportunities, and our future as a species.[citation needed]

The term “ecosystem” was first used in 1935 in a publication by British ecologist Arthur Tansley.[fn 1][37] Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment.[38] He later refined the term, describing it as “The whole system, … including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment”.[39] Tansley regarded ecosystems not simply as natural units, but as “mental isolates”.[39] Tansley later defined the spatial extent of ecosystems using the term ecotope.[40]

G. Evelyn Hutchinson, a limnologist who was a contemporary of Tansley’s, combined Charles Elton’s ideas about trophic ecology with those of Russian geochemist Vladimir Vernadsky. As a result he suggested that mineral nutrient availability in a lake limited algal production. This would, in turn, limit the abundance of animals that feed on algae. Raymond Lindeman took these ideas further to suggest that the flow of energy through a lake was the primary driver of the ecosystem. Hutchinson’s students, brothers Howard T. Odum and Eugene P. Odum, further developed a “systems approach” to the study of ecosystems. This allowed them to study the flow of energy and material through ecological systems.[38]

Read the rest here:

Ecosystem – Wikipedia

Ecosystem – Wikipedia

This article is about natural ecosystems. For the term used in man-made systems, see Digital ecosystem.

An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment (such as air, water and mineral soil), interacting as a system.[2] (However, there is no single definition of what constitutes an ecosystem.[3]) These biotic and abiotic components are linked together through nutrient cycles and energy flows.[4] Ecosystems are defined by the network of interactions among organisms, and between organisms and their environment.[5] They can be of any size but usually encompass specific, limited spaces[6] (although some scientists say that the entire planet is an ecosystem).[7] Energy, water, nitrogen and soil minerals are other essential abiotic components of an ecosystem.

The energy that flows through ecosystems is obtained primarily from the sun. It generally enters the system through photosynthesis, a process that also captures carbon dioxide from the atmosphere. Animals play an important role in the movement of matter and energy through the system. They also influence the quantity of plant and microbial biomass present. By breaking down dead organic matter, decomposers release carbon back to the atmosphere. This process also facilitates nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and other microbes.[8]

Ecosystems are controlled both by external and internal factors. External factors such as climate, the parent material that forms the soil, and topography control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem.[9] Other external factors include time and potential biota. Ecosystems are dynamic entities. As such, they are subject to periodic disturbances and are in the process of recovering from some past disturbance.[10] Internal factors not only control ecosystem processes but are also controlled by them and are often subject to feedback loops.[9] The resource inputs are generally controlled by external processes like climate and parent material. The availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading.[9] Other internal factors include disturbance, succession and the types of species present. Biodiversity affects ecosystem function.

Humans exist and operate within ecosystems. The cumulative effects of human activities are large enough to influence external factors like climate,[9] leading to climate change. Ecosystems provide a variety of goods and services upon which people depend. Ecosystem management suggests that rather than managing individual species, natural resources should be managed at the level of the ecosystem itself. Ecosystem services are in many cases threatened by human activities.

There is no single definition of what constitutes an ecosystem.[3] German ecologist Ernst-Detlef Schulze and coauthors defined an ecosystem as an area which is “uniform regarding the biological turnover, and contains all the fluxes above and below the ground area under consideration.” They explicitly reject Gene Likens’ use of entire river catchments as “too wide a demarcation” to be a single ecosystem, given the level of heterogeneity within such an area.[11] Other authors have suggested that an ecosystem can encompass a much larger area, even the whole planet.[7] Schulze and coauthors also rejected the idea that a single rotting log could be studied as an ecosystem because the size of the flows between the log and its surroundings are too large, relative to the proportion cycles within the log.[11] Philosopher of science Mark Sagoff considers the failure to define “the kind of object it studies” to be an obstacle to the development of theory in ecosystem ecology.[3]

Ecosystems can be studied through a variety of approachestheoretical studies, studies monitoring specific ecosystems over long periods of time, those that look at differences between ecosystems to elucidate how they work and direct manipulative experimentation.[12] Studies can be carried out at a variety of scales, from microcosms and mesocosms which serve as simplified representations of ecosystems, through whole-ecosystem studies.[13] American ecologist Stephen R. Carpenter has argued that microcosm experiments can be “irrelevant and diversionary” if they are not carried out in conjunction with field studies carried out at the ecosystem scale, because microcosm experiments often fail to accurately predict ecosystem-level dynamics.[14]

The Hubbard Brook Ecosystem Study, established in the White Mountains, New Hampshire in 1963, was the first successful attempt to study an entire watershed as an ecosystem. The study used stream chemistry as a means of monitoring ecosystem properties, and developed a detailed biogeochemical model of the ecosystem.[15] Long-term research at the site led to the discovery of acid rain in North America in 1972, and was able to document the consequent depletion of soil cations (especially calcium) over the next several decades.[16]

The term “ecosystem” is often used very imprecisely and linked with a descriptive term (adjective) even if those systems are rather biomes, not ecosystems.[citation needed] Examples include: terrestrial ecosystem or aquatic ecosystems. Aquatic ecosystems are split into marine ecosystems (Large marine ecosystem is another term used) and freshwater ecosystems.

Ecosystems are controlled both by external and internal factors. External factors, also called state factors, control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem. The most important of these is climate.[9] Climate determines the biome in which the ecosystem is embedded. Rainfall patterns and temperature seasonality determine the amount of water available to the ecosystem and the supply of energy available (by influencing photosynthesis).[9]

Parent material, the underlying geological material that gives rise to soils, determines the nature of the soils present, and influences the supply of mineral nutrients. Topography also controls ecosystem processes by affecting things like microclimate, soil development and the movement of water through a system. This may be the difference between the ecosystem present in wetland situated in a small depression on the landscape, and one present on an adjacent steep hillside.[9]

Other external factors that play an important role in ecosystem functioning include time and potential biota. Similarly, the set of organisms that can potentially be present in an area can also have a major impact on ecosystems. Ecosystems in similar environments that are located in different parts of the world can end up doing things very differently simply because they have different pools of species present.[9] The introduction of non-native species can cause substantial shifts in ecosystem function.

Unlike external factors, internal factors in ecosystems not only control ecosystem processes, but are also controlled by them. Consequently, they are often subject to feedback loops.[9] While the resource inputs are generally controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading.[9] Other factors like disturbance, succession or the types of species present are also internal factors.

Primary production is the production of organic matter from inorganic carbon sources. This mainly occurs through photosynthesis. The energy incorporated through this process supports life on earth, while the carbon makes up much of the organic matter in living and dead biomass, soil carbon and fossil fuels. It also drives the carbon cycle, which influences global climate via the greenhouse effect.

Through the process of photosynthesis, plants capture energy from light and use it to combine carbon dioxide and water to produce carbohydrates and oxygen. The photosynthesis carried out by all the plants in an ecosystem is called the gross primary production (GPP).[17] About 4860% of the GPP is consumed in plant respiration.

The remainder, that portion of GPP that is not used up by respiration, is known as the net primary production (NPP).[18]

Energy and carbon enter ecosystems through photosynthesis, are incorporated into living tissue, transferred to other organisms that feed on the living and dead plant matter, and eventually released through respiration.[18]

The carbon and energy incorporated into plant tissues (net primary production) is either consumed by animals while the plant is alive, or it remains uneaten when the plant tissue dies and becomes detritus. In terrestrial ecosystems, roughly 90% of the net primary production ends up being broken down by decomposers. The remainder is either consumed by animals while still alive and enters the plant-based trophic system, or it is consumed after it has died, and enters the detritus-based trophic system.

In aquatic systems, the proportion of plant biomass that gets consumed by herbivores is much higher.[19] In trophic systems photosynthetic organisms are the primary producers. The organisms that consume their tissues are called primary consumers or secondary producersherbivores. Organisms which feed on microbes (bacteria and fungi) are termed microbivores. Animals that feed on primary consumerscarnivoresare secondary consumers. Each of these constitutes a trophic level.[19]

The sequence of consumptionfrom plant to herbivore, to carnivoreforms a food chain. Real systems are much more complex than thisorganisms will generally feed on more than one form of food, and may feed at more than one trophic level. Carnivores may capture some prey which are part of a plant-based trophic system and others that are part of a detritus-based trophic system (a bird that feeds both on herbivorous grasshoppers and earthworms, which consume detritus). Real systems, with all these complexities, form food webs rather than food chains.[19]

Ecosystem ecology studies “the flow of energy and materials through organisms and the physical environment”. It seeks to understand the processes which govern the stocks of material and energy in ecosystems, and the flow of matter and energy through them. The study of ecosystems can cover 10 orders of magnitude, from the surface layers of rocks to the surface of the planet.[20]

The carbon and nutrients in dead organic matter are broken down by a group of processes known as decomposition. This releases nutrients that can then be re-used for plant and microbial production, and returns carbon dioxide to the atmosphere (or water) where it can be used for photosynthesis. In the absence of decomposition, dead organic matter would accumulate in an ecosystem, and nutrients and atmospheric carbon dioxide would be depleted.[21] Approximately 90% of terrestrial net primary production goes directly from plant to decomposer.[19]

Decomposition processes can be separated into three categoriesleaching, fragmentation and chemical alteration of dead material.

As water moves through dead organic matter, it dissolves and carries with it the water-soluble components. These are then taken up by organisms in the soil, react with mineral soil, or are transported beyond the confines of the ecosystem (and are considered lost to it).[21] Newly shed leaves and newly dead animals have high concentrations of water-soluble components, and include sugars, amino acids and mineral nutrients. Leaching is more important in wet environments, and much less important in dry ones.[21]

Fragmentation processes break organic material into smaller pieces, exposing new surfaces for colonization by microbes. Freshly shed leaf litter may be inaccessible due to an outer layer of cuticle or bark, and cell contents are protected by a cell wall. Newly dead animals may be covered by an exoskeleton. Fragmentation processes, which break through these protective layers, accelerate the rate of microbial decomposition.[21] Animals fragment detritus as they hunt for food, as does passage through the gut. Freeze-thaw cycles and cycles of wetting and drying also fragment dead material.[21]

The chemical alteration of dead organic matter is primarily achieved through bacterial and fungal action. Fungal hyphae produce enzymes which can break through the tough outer structures surrounding dead plant material. They also produce enzymes which break down lignin, which allows them access to both cell contents and to the nitrogen in the lignin. Fungi can transfer carbon and nitrogen through their hyphal networks and thus, unlike bacteria, are not dependent solely on locally available resources.[21]

Decomposition rates vary among ecosystems. The rate of decomposition is governed by three sets of factorsthe physical environment (temperature, moisture and soil properties), the quantity and quality of the dead material available to decomposers, and the nature of the microbial community itself.[22] Temperature controls the rate of microbial respiration; the higher the temperature, the faster microbial decomposition occurs. It also affects soil moisture, which slows microbial growth and reduces leaching. Freeze-thaw cycles also affect decompositionfreezing temperatures kill soil microorganisms, which allows leaching to play a more important role in moving nutrients around. This can be especially important as the soil thaws in the spring, creating a pulse of nutrients which become available.[22]

Decomposition rates are low under very wet or very dry conditions. Decomposition rates are highest in wet, moist conditions with adequate levels of oxygen. Wet soils tend to become deficient in oxygen (this is especially true in wetlands), which slows microbial growth. In dry soils, decomposition slows as well, but bacteria continue to grow (albeit at a slower rate) even after soils become too dry to support plant growth.

Ecosystems continually exchange energy and carbon with the wider environment. Mineral nutrients, on the other hand, are mostly cycled back and forth between plants, animals, microbes and the soil. Most nitrogen enters ecosystems through biological nitrogen fixation, is deposited through precipitation, dust, gases or is applied as fertilizer.[23]

Since most terrestrial ecosystems are nitrogen-limited, nitrogen cycling is an important control on ecosystem production.[23]

Until modern times, nitrogen fixation was the major source of nitrogen for ecosystems. Nitrogen fixing bacteria either live symbiotically with plants, or live freely in the soil. The energetic cost is high for plants which support nitrogen-fixing symbiontsas much as 25% of gross primary production when measured in controlled conditions. Many members of the legume plant family support nitrogen-fixing symbionts. Some cyanobacteria are also capable of nitrogen fixation. These are phototrophs, which carry out photosynthesis. Like other nitrogen-fixing bacteria, they can either be free-living or have symbiotic relationships with plants.[23] Other sources of nitrogen include acid deposition produced through the combustion of fossil fuels, ammonia gas which evaporates from agricultural fields which have had fertilizers applied to them, and dust.[23] Anthropogenic nitrogen inputs account for about 80% of all nitrogen fluxes in ecosystems.[23]

When plant tissues are shed or are eaten, the nitrogen in those tissues becomes available to animals and microbes. Microbial decomposition releases nitrogen compounds from dead organic matter in the soil, where plants, fungi and bacteria compete for it. Some soil bacteria use organic nitrogen-containing compounds as a source of carbon, and release ammonium ions into the soil. This process is known as nitrogen mineralization. Others convert ammonium to nitrite and nitrate ions, a process known as nitrification. Nitric oxide and nitrous oxide are also produced during nitrification.[23] Under nitrogen-rich and oxygen-poor conditions, nitrates and nitrites are converted to nitrogen gas, a process known as denitrification.[23]

Other important nutrients include phosphorus, sulfur, calcium, potassium, magnesium and manganese.[24] Phosphorus enters ecosystems through weathering. As ecosystems age this supply diminishes, making phosphorus-limitation more common in older landscapes (especially in the tropics).[24] Calcium and sulfur are also produced by weathering, but acid deposition is an important source of sulfur in many ecosystems. Although magnesium and manganese are produced by weathering, exchanges between soil organic matter and living cells account for a significant portion of ecosystem fluxes. Potassium is primarily cycled between living cells and soil organic matter.[24]

Biodiversity plays an important role in ecosystem functioning.[26] The reason for this is that ecosystem processes are driven by the number of species in an ecosystem, the exact nature of each individual species, and the relative abundance organisms within these species.[27] Ecosystem processes are broad generalizations that actually take place through the actions of individual organisms. The nature of the organismsthe species, functional groups and trophic levels to which they belongdictates the sorts of actions these individuals are capable of carrying out, and the relative efficiency with which they do so.

Ecological theory suggests that in order to coexist, species must have some level of limiting similaritythey must be different from one another in some fundamental way, otherwise one species would competitively exclude the other.[28] Despite this, the cumulative effect of additional species in an ecosystem is not linearadditional species may enhance nitrogen retention, for example, but beyond some level of species richness, additional species may have little additive effect.[27]

The addition (or loss) of species which are ecologically similar to those already present in an ecosystem tends to only have a small effect on ecosystem function. Ecologically distinct species, on the other hand, have a much larger effect. Similarly, dominant species have a large impact on ecosystem function, while rare species tend to have a small effect. Keystone species tend to have an effect on ecosystem function that is disproportionate to their abundance in an ecosystem.[27] Similarly, an ecosystem engineer is any organism that creates, significantly modifies, maintains or destroys a habitat.

Ecosystems are dynamic entities. They are subject to periodic disturbances and are in the process of recovering from some past disturbance.[10] When a perturbation occurs, an ecoystem responds by moving away from its initial state. The tendency of an ecosystem to remain close to its equilibrium state, despite that disturbance, is termed its resistance. On the other hand, the speed with which it returns to its initial state after disturbance is called its resilience.[10] Time plays a role in the development of soil from bare rock and the recovery of a community from disturbance.[9]

From one year to another, ecosystems experience variation in their biotic and abiotic environments. A drought, an especially cold winter and a pest outbreak all constitute short-term variability in environmental conditions. Animal populations vary from year to year, building up during resource-rich periods and crashing as they overshoot their food supply. These changes play out in changes in net primary production decomposition rates, and other ecosystem processes.[10] Longer-term changes also shape ecosystem processesthe forests of eastern North America still show legacies of cultivation which ceased 200 years ago, while methane production in eastern Siberian lakes is controlled by organic matter which accumulated during the Pleistocene.[10]

Disturbance also plays an important role in ecological processes. F. Stuart Chapin and coauthors define disturbance as “a relatively discrete event in time and space that alters the structure of populations, communities and ecosystems and causes changes in resources availability or the physical environment”.[29] This can range from tree falls and insect outbreaks to hurricanes and wildfires to volcanic eruptions. Such disturbances can cause large changes in plant, animal and microbe populations, as well soil organic matter content.[10] Disturbance is followed by succession, a “directional change in ecosystem structure and functioning resulting from biotically driven changes in resources supply.”[29]

The frequency and severity of disturbance determines the way it impacts ecosystem function. Major disturbance like a volcanic eruption or glacial advance and retreat leave behind soils that lack plants, animals or organic matter. Ecosystems that experience such disturbances undergo primary succession. Less severe disturbance like forest fires, hurricanes or cultivation result in secondary succession and a faster recovery.[10] More severe disturbance and more frequent disturbance result in longer recovery times.

Classifying ecosystems into ecologically homogeneous units is an important step towards effective ecosystem management.[30] There is no single, agreed-upon way to do this. A variety of systems exist, based on vegetation cover, remote sensing, and bioclimatic classification systems.[30]

Ecological land classification is a cartographical delineation or regionalisation of distinct ecological areas, identified by their geology, topography, soils, vegetation, climate conditions, living species, habitats, water resources, and sometimes also anthropic factors.[31]

Human activities are important in almost all ecosystems. Although humans exist and operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.[9]

Ecosystems provide a variety of goods and services upon which people depend.[32] Ecosystem goods include the “tangible, material products” of ecosystem processes such as food, construction material, medicinal plants.[33] They also include less tangible items like tourism and recreation, and genes from wild plants and animals that can be used to improve domestic species.[32]

Ecosystem services, on the other hand, are generally “improvements in the condition or location of things of value”.[33] These include things like the maintenance of hydrological cycles, cleaning air and water, the maintenance of oxygen in the atmosphere, crop pollination and even things like beauty, inspiration and opportunities for research.[32] While ecosystem goods have traditionally been recognized as being the basis for things of economic value, ecosystem services tend to be taken for granted.[33]

When natural resource management is applied to whole ecosystems, rather than single species, it is termed ecosystem management.[34] Although definitions of ecosystem management abound, there is a common set of principles which underlie these definitions.[35] A fundamental principle is the long-term sustainability of the production of goods and services by the ecosystem;[35] “intergenerational sustainability [is] a precondition for management, not an afterthought”.[32]

While ecosystem management can be used as part of a plan for wilderness conservation, it can also be used in intensively managed ecosystems[32] (see, for example, agroecosystem and close to nature forestry).

As human populations and per capita consumption grow, so do the resource demands imposed on ecosystems and the impacts of the human ecological footprint. Natural resources are vulnerable and limited. The environmental impacts of anthropogenic actions are becoming more apparent. Problems for all ecosystems include: environmental pollution, climate change and biodiversity loss. For terrestrial ecosystems further threats include air pollution, soil degradation, and deforestation. For aquatic ecosystems threats include also unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollution, microplastics pollution, water pollution, and building on coastal areas.[36]

Society is increasingly becoming aware that ecosystem services are not only limited, but also that they are threatened by human activities. The need to better consider long-term ecosystem health and its role in enabling human habitation and economic activity is urgent. To help inform decision-makers, many ecosystem services are being assigned economic values, often based on the cost of replacement with anthropogenic alternatives. The ongoing challenge of prescribing economic value to nature, for example through biodiversity banking, is prompting transdisciplinary shifts in how we recognize and manage the environment, social responsibility, business opportunities, and our future as a species.[citation needed]

The term “ecosystem” was first used in 1935 in a publication by British ecologist Arthur Tansley.[fn 1][37] Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment.[38] He later refined the term, describing it as “The whole system, … including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment”.[39] Tansley regarded ecosystems not simply as natural units, but as “mental isolates”.[39] Tansley later defined the spatial extent of ecosystems using the term ecotope.[40]

G. Evelyn Hutchinson, a limnologist who was a contemporary of Tansley’s, combined Charles Elton’s ideas about trophic ecology with those of Russian geochemist Vladimir Vernadsky. As a result he suggested that mineral nutrient availability in a lake limited algal production. This would, in turn, limit the abundance of animals that feed on algae. Raymond Lindeman took these ideas further to suggest that the flow of energy through a lake was the primary driver of the ecosystem. Hutchinson’s students, brothers Howard T. Odum and Eugene P. Odum, further developed a “systems approach” to the study of ecosystems. This allowed them to study the flow of energy and material through ecological systems.[38]

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Ecosystem – Wikipedia

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Since 2014 Eyal has been working in the cryptocurrency space, beginning with AppCoin, empowering local communities with local currencies, and now Bancor Protocol, an on-chain, fully decentralized conversion solution between tokens connected to the network, through a low-cost, perpetual and adjustable smart contract liquidity mechanism. Bancor successfully completed a record-breaking token sale in June 2017, raising over $153 million for BNT, the Bancor Network Token, which serves as the hub connector for the Bancor Network, a decentralized liquidity network allowing every integrated token to be instantly converted to any other, with no counterparty.

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Ecosystem – Wikipedia

This article is about natural ecosystems. For the term used in man-made systems, see Digital ecosystem.

An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment (things like air, water and mineral soil), interacting as a system.[2] These biotic and abiotic components are regarded as linked together through nutrient cycles and energy flows.[3] As ecosystems are defined by the network of interactions among organisms, and between organisms and their environment,[4] they can be of any size but usually encompass specific, limited spaces[5] (although some scientists say that the entire planet is an ecosystem).[6] Energy, water, nitrogen and soil minerals are other essential abiotic components of an ecosystem. The energy that flows through ecosystems is obtained primarily from the sun. It generally enters the system through photosynthesis, a process that also captures carbon dioxide from the atmosphere. By feeding on plants and on one another, animals play an important role in the movement of matter and energy through the system. They also influence the quantity of plant and microbial biomass present. By breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and other microbes.[7]

Ecosystems are controlled both by external and internal factors. External factors such as climate, the parent material that forms the soil, and topography control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem.[8] Other external factors include time and potential biota. Ecosystems are dynamic entitiesinvariably, they are subject to periodic disturbances and are in the process of recovering from some past disturbance.[9] Ecosystems in similar environments that are located in different parts of the world can have very different characteristics simply because they contain different species.[8] The introduction of non-native species can cause substantial shifts in ecosystem function. Internal factors not only control ecosystem processes but are also controlled by them and are often subject to feedback loops.[8] While the resource inputs are generally controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading.[8] Other internal factors include disturbance, succession and the types of species present. Although humans exist and operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.[8]

Biodiversity affects ecosystem function, as do the processes of disturbance and succession. Ecosystems provide a variety of goods and services upon which people depend; the principles of ecosystem management suggest that rather than managing individual species, natural resources should be managed at the level of the ecosystem itself. Classifying ecosystems into ecologically homogeneous units is an important step towards effective ecosystem management, but there is no single, agreed-upon way to do this.

The term “ecosystem” was first used in 1935 in a publication by British ecologist Arthur Tansley.[fn 1][10] Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment.[11] He later refined the term, describing it as “The whole system, … including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment”.[12] Tansley regarded ecosystems not simply as natural units, but as mental isolates.[12] Tansley later[13] defined the spatial extent of ecosystems using the term ecotope.

G. Evelyn Hutchinson, a pioneering limnologist who was a contemporary of Tansley’s, combined Charles Elton’s ideas about trophic ecology with those of Russian geochemist Vladimir Vernadsky to suggest that mineral nutrient availability in a lake limited algal production which would, in turn, limit the abundance of animals that feed on algae. Raymond Lindeman took these ideas one step further to suggest that the flow of energy through a lake was the primary driver of the ecosystem. Hutchinson’s students, brothers Howard T. Odum and Eugene P. Odum, further developed a “systems approach” to the study of ecosystems, allowing them to study the flow of energy and material through ecological systems.[11]

Energy and carbon enter ecosystems through photosynthesis, are incorporated into living tissue, transferred to other organisms that feed on the living and dead plant matter, and eventually released through respiration.[14] Most mineral nutrients, on the other hand, are recycled within ecosystems.[15]

Ecosystems are controlled both by external and internal factors. External factors, also called state factors, control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem. The most important of these is climate.[8] Climate determines the biome in which the ecosystem is embedded. Rainfall patterns and temperature seasonality determine the amount of water available to the ecosystem and the supply of energy available (by influencing photosynthesis).[8] Parent material, the underlying geological material that gives rise to soils, determines the nature of the soils present, and influences the supply of mineral nutrients. Topography also controls ecosystem processes by affecting things like microclimate, soil development and the movement of water through a system. This may be the difference between the ecosystem present in wetland situated in a small depression on the landscape, and one present on an adjacent steep hillside.[8]

Other external factors that play an important role in ecosystem functioning include time and potential biota. Ecosystems are dynamic entitiesinvariably, they are subject to periodic disturbances and are in the process of recovering from some past disturbance.[9] Time plays a role in the development of soil from bare rock and the recovery of a community from disturbance.[8] Similarly, the set of organisms that can potentially be present in an area can also have a major impact on ecosystems. Ecosystems in similar environments that are located in different parts of the world can end up doing things very differently simply because they have different pools of species present.[8] The introduction of non-native species can cause substantial shifts in ecosystem function.

Unlike external factors, internal factors in ecosystems not only control ecosystem processes, but are also controlled by them. Consequently, they are often subject to feedback loops.[8] While the resource inputs are generally controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading.[8] Other factors like disturbance, succession or the types of species present are also internal factors. Human activities are important in almost all ecosystems. Although humans exist and operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.[8]

Primary production is the production of organic matter from inorganic carbon sources. Overwhelmingly, this occurs through photosynthesis. The energy incorporated through this process supports life on earth, while the carbon makes up much of the organic matter in living and dead biomass, soil carbon and fossil fuels. It also drives the carbon cycle, which influences global climate via the greenhouse effect.

Through the process of photosynthesis, plants capture energy from light and use it to combine carbon dioxide and water to produce carbohydrates and oxygen. The photosynthesis carried out by all the plants in an ecosystem is called the gross primary production (GPP).[16] About 4860% of the GPP is consumed in plant respiration. The remainder, that portion of GPP that is not used up by respiration, is known as the net primary production (NPP).[14] Total photosynthesis is limited by a range of environmental factors. These include the amount of light available, the amount of leaf area a plant has to capture light (shading by other plants is a major limitation of photosynthesis), rate at which carbon dioxide can be supplied to the chloroplasts to support photosynthesis, the availability of water, and the availability of suitable temperatures for carrying out photosynthesis.[16]

The carbon and energy incorporated into plant tissues (net primary production) is either consumed by animals while the plant is alive, or it remains uneaten when the plant tissue dies and becomes detritus. In terrestrial ecosystems, roughly 90% of the NPP ends up being broken down by decomposers. The remainder is either consumed by animals while still alive and enters the plant-based trophic system, or it is consumed after it has died, and enters the detritus-based trophic system. In aquatic systems, the proportion of plant biomass that gets consumed by herbivores is much higher.[18] In trophic systems photosynthetic organisms are the primary producers. The organisms that consume their tissues are called primary consumers or secondary producersherbivores. Organisms which feed on microbes (bacteria and fungi) are termed microbivores. Animals that feed on primary consumerscarnivoresare secondary consumers. Each of these constitutes a trophic level.[18] The sequence of consumptionfrom plant to herbivore, to carnivoreforms a food chain. Real systems are much more complex than thisorganisms will generally feed on more than one form of food, and may feed at more than one trophic level. Carnivores may capture some prey which are part of a plant-based trophic system and others that are part of a detritus-based trophic system (a bird that feeds both on herbivorous grasshoppers and earthworms, which consume detritus). Real systems, with all these complexities, form food webs rather than food chains.[18]

The carbon and nutrients in dead organic matter are broken down by a group of processes known as decomposition. This releases nutrients that can then be re-used for plant and microbial production, and returns carbon dioxide to the atmosphere (or water) where it can be used for photosynthesis. In the absence of decomposition, dead organic matter would accumulate in an ecosystem and nutrients and atmospheric carbon dioxide would be depleted.[19] Approximately 90% of terrestrial NPP goes directly from plant to decomposer.[18]

Decomposition processes can be separated into three categoriesleaching, fragmentation and chemical alteration of dead material. As water moves through dead organic matter, it dissolves and carries with it the water-soluble components. These are then taken up by organisms in the soil, react with mineral soil, or are transported beyond the confines of the ecosystem (and are considered lost to it).[19] Newly shed leaves and newly dead animals have high concentrations of water-soluble components, and include sugars, amino acids and mineral nutrients. Leaching is more important in wet environments, and much less important in dry ones.[19]

Fragmentation processes break organic material into smaller pieces, exposing new surfaces for colonization by microbes. Freshly shed leaf litter may be inaccessible due to an outer layer of cuticle or bark, and cell contents are protected by a cell wall. Newly dead animals may be covered by an exoskeleton. Fragmentation processes, which break through these protective layers, accelerate the rate of microbial decomposition.[19] Animals fragment detritus as they hunt for food, as does passage through the gut. Freeze-thaw cycles and cycles of wetting and drying also fragment dead material.[19]

The chemical alteration of dead organic matter is primarily achieved through bacterial and fungal action. Fungal hyphae produce enzymes which can break through the tough outer structures surrounding dead plant material. They also produce enzymes which break down lignin, which allows them access to both cell contents and to the nitrogen in the lignin. Fungi can transfer carbon and nitrogen through their hyphal networks and thus, unlike bacteria, are not dependent solely on locally available resources.[19]

Decomposition rates vary among ecosystems. The rate of decomposition is governed by three sets of factorsthe physical environment (temperature, moisture and soil properties), the quantity and quality of the dead material available to decomposers, and the nature of the microbial community itself.[20] Temperature controls the rate of microbial respiration; the higher the temperature, the faster microbial decomposition occurs. It also affects soil moisture, which slows microbial growth and reduces leaching. Freeze-thaw cycles also affect decompositionfreezing temperatures kill soil microorganisms, which allows leaching to play a more important role in moving nutrients around. This can be especially important as the soil thaws in the Spring, creating a pulse of nutrients which become available.[20]

Decomposition rates are low under very wet or very dry conditions. Decomposition rates are highest in wet, moist conditions with adequate levels of oxygen. Wet soils tend to become deficient in oxygen (this is especially true in wetlands), which slows microbial growth. In dry soils, decomposition slows as well, but bacteria continue to grow (albeit at a slower rate) even after soils become too dry to support plant growth. When the rains return and soils become wet, the osmotic gradient between the bacterial cells and the soil water causes the cells to gain water quickly. Under these conditions, many bacterial cells burst, releasing a pulse of nutrients.[20] Decomposition rates also tend to be slower in acidic soils.[20] Soils which are rich in clay minerals tend to have lower decomposition rates, and thus, higher levels of organic matter.[20] The smaller particles of clay result in a larger surface area that can hold water. The higher the water content of a soil, the lower the oxygen content[21] and consequently, the lower the rate of decomposition. Clay minerals also bind particles of organic material to their surface, making them less accessibly to microbes.[20] Soil disturbance like tilling increase decomposition by increasing the amount of oxygen in the soil and by exposing new organic matter to soil microbes.[20]

The quality and quantity of the material available to decomposers is another major factor that influences the rate of decomposition. Substances like sugars and amino acids decompose readily and are considered labile. Cellulose and hemicellulose, which are broken down more slowly, are “moderately labile”. Compounds which are more resistant to decay, like lignin or cutin, are considered recalcitrant.[20] Litter with a higher proportion of labile compounds decomposes much more rapidly than does litter with a higher proportion of recalcitrant material. Consequently, dead animals decompose more rapidly than dead leaves, which themselves decompose more rapidly than fallen branches.[20] As organic material in the soil ages, its quality decreases. The more labile compounds decompose quickly, leaving an increasing proportion of recalcitrant material. Microbial cell walls also contain recalcitrant materials like chitin, and these also accumulate as the microbes die, further reducing the quality of older soil organic matter.[20]

Ecosystems continually exchange energy and carbon with the wider environment; mineral nutrients, on the other hand, are mostly cycled back and forth between plants, animals, microbes and the soil. Most nitrogen enters ecosystems through biological nitrogen fixation, is deposited through precipitation, dust, gases or is applied as fertilizer.[15] Since most terrestrial ecosystems are nitrogen-limited, nitrogen cycling is an important control on ecosystem production.[15]

Until modern times, nitrogen fixation was the major source of nitrogen for ecosystems. Nitrogen fixing bacteria either live symbiotically with plants, or live freely in the soil. The energetic cost is high for plants which support nitrogen-fixing symbiontsas much as 25% of GPP when measured in controlled conditions. Many members of the legume plant family support nitrogen-fixing symbionts. Some cyanobacteria are also capable of nitrogen fixation. These are phototrophs, which carry out photosynthesis. Like other nitrogen-fixing bacteria, they can either be free-living or have symbiotic relationships with plants.[15] Other sources of nitrogen include acid deposition produced through the combustion of fossil fuels, ammonia gas which evaporates from agricultural fields which have had fertilizers applied to them, and dust.[15] Anthropogenic nitrogen inputs account for about 80% of all nitrogen fluxes in ecosystems.[15]

When plant tissues are shed or are eaten, the nitrogen in those tissues becomes available to animals and microbes. Microbial decomposition releases nitrogen compounds from dead organic matter in the soil, where plants, fungi and bacteria compete for it. Some soil bacteria use organic nitrogen-containing compounds as a source of carbon, and release ammonium ions into the soil. This process is known as nitrogen mineralization. Others convert ammonium to nitrite and nitrate ions, a process known as nitrification. Nitric oxide and nitrous oxide are also produced during nitrification.[15] Under nitrogen-rich and oxygen-poor conditions, nitrates and nitrites are converted to nitrogen gas, a process known as denitrification.[15]

Other important nutrients include phosphorus, sulfur, calcium, potassium, magnesium and manganese.[22] Phosphorus enters ecosystems through weathering. As ecosystems age this supply diminishes, making phosphorus-limitation more common in older landscapes (especially in the tropics).[22] Calcium and sulfur are also produced by weathering, but acid deposition is an important source of sulfur in many ecosystems. Although magnesium and manganese are produced by weathering, exchanges between soil organic matter and living cells account for a significant portion of ecosystem fluxes. Potassium is primarily cycled between living cells and soil organic matter.[22]

Ecosystem processes are broad generalizations that actually take place through the actions of individual organisms. The nature of the organismsthe species, functional groups and trophic levels to which they belongdictates the sorts of actions these individuals are capable of carrying out, and the relative efficiency with which they do so. Thus, ecosystem processes are driven by the number of species in an ecosystem, the exact nature of each individual species, and the relative abundance organisms within these species.[24] Biodiversity plays an important role in ecosystem functioning.[25]

Ecological theory suggests that in order to coexist, species must have some level of limiting similaritythey must be different from one another in some fundamental way, otherwise one species would competitively exclude the other.[26] Despite this, the cumulative effect of additional species in an ecosystem is not linearadditional species may enhance nitrogen retention, for example, but beyond some level of species richness, additional species may have little additive effect.[24] The addition (or loss) of species which are ecologically similar to those already present in an ecosystem tends to only have a small effect on ecosystem function. Ecologically distinct species, on the other hand, have a much larger effect. Similarly, dominant species have a large impact on ecosystem function, while rare species tend to have a small effect. Keystone species tend to have an effect on ecosystem function that is disproportionate to their abundance in an ecosystem.[24]

Ecosystems provide a variety of goods and services upon which people depend.[27] Ecosystem goods include the “tangible, material products”[28] of ecosystem processesfood, construction material, medicinal plantsin addition to less tangible items like tourism and recreation, and genes from wild plants and animals that can be used to improve domestic species.[27] Ecosystem services, on the other hand, are generally “improvements in the condition or location of things of value”.[28] These include things like the maintenance of hydrological cycles, cleaning air and water, the maintenance of oxygen in the atmosphere, crop pollination and even things like beauty, inspiration and opportunities for research.[27] While ecosystem goods have traditionally been recognized as being the basis for things of economic value, ecosystem services tend to be taken for granted.[28] While Gretchen Daily’s original definition distinguished between ecosystem goods and ecosystem services, Robert Costanza and colleagues’ later work and that of the Millennium Ecosystem Assessment lumped all of these together as ecosystem services.[28][29]

When natural resource management is applied to whole ecosystems, rather than single species, it is termed ecosystem management.[30] A variety of definitions exist: F. Stuart Chapin and coauthors define it as “the application of ecological science to resource management to promote long-term sustainability of ecosystems and the delivery of essential ecosystem goods and services”,[31] while Norman Christensen and coauthors defined it as “management driven by explicit goals, executed by policies, protocols, and practices, and made adaptable by monitoring and research based on our best understanding of the ecological interactions and processes necessary to sustain ecosystem structure and function”[27] and Peter Brussard and colleagues defined it as “managing areas at various scales in such a way that ecosystem services and biological resources are preserved while appropriate human use and options for livelihood are sustained”.[32]

Although definitions of ecosystem management abound, there is a common set of principles which underlie these definitions.[31] A fundamental principle is the long-term sustainability of the production of goods and services by the ecosystem;[31] “intergenerational sustainability [is] a precondition for management, not an afterthought”.[27] It also requires clear goals with respect to future trajectories and behaviors of the system being managed. Other important requirements include a sound ecological understanding of the system, including connectedness, ecological dynamics and the context in which the system is embedded. Other important principles include an understanding of the role of humans as components of the ecosystems and the use of adaptive management.[27] While ecosystem management can be used as part of a plan for wilderness conservation, it can also be used in intensively managed ecosystems[27] (see, for example, agroecosystem and close to nature forestry).

Ecosystems are dynamic entitiesinvariably, they are subject to periodic disturbances and are in the process of recovering from some past disturbance.[9] When an ecosystem is subject to some sort of perturbation, it responds by moving away from its initial state. The tendency of a system to remain close to its equilibrium state, despite that disturbance, is termed its resistance. On the other hand, the speed with which it returns to its initial state after disturbance is called its resilience.[9]

From one year to another, ecosystems experience variation in their biotic and abiotic environments. A drought, an especially cold winter and a pest outbreak all constitute short-term variability in environmental conditions. Animal populations vary from year to year, building up during resource-rich periods and crashing as they overshoot their food supply. These changes play out in changes in NPP, decomposition rates, and other ecosystem processes.[9] Longer-term changes also shape ecosystem processesthe forests of eastern North America still show legacies of cultivation which ceased 200 years ago, while methane production in eastern Siberian lakes is controlled by organic matter which accumulated during the Pleistocene.[9]

Disturbance also plays an important role in ecological processes. F. Stuart Chapin and coauthors define disturbance as “a relatively discrete event in time and space that alters the structure of populations, communities and ecosystems and causes changes in resources availability or the physical environment”.[33] This can range from tree falls and insect outbreaks to hurricanes and wildfires to volcanic eruptions and can cause large changes in plant, animal and microbe populations, as well soil organic matter content.[9] Disturbance is followed by succession, a “directional change in ecosystem structure and functioning resulting from biotically driven changes in resources supply.”[33]

The frequency and severity of disturbance determines the way it impacts ecosystem function. Major disturbance like a volcanic eruption or glacial advance and retreat leave behind soils that lack plants, animals or organic matter. Ecosystems that experience disturbances that undergo primary succession. Less severe disturbance like forest fires, hurricanes or cultivation result in secondary succession.[9] More severe disturbance and more frequent disturbance result in longer recovery times. Ecosystems recover more quickly from less severe disturbance events.[9]

The early stages of primary succession are dominated by species with small propagules (seed and spores) which can be dispersed long distances. The early colonizersoften algae, cyanobacteria and lichensstabilize the substrate. Nitrogen supplies are limited in new soils, and nitrogen-fixing species tend to play an important role early in primary succession. Unlike in primary succession, the species that dominate secondary succession, are usually present from the start of the process, often in the soil seed bank. In some systems the successional pathways are fairly consistent, and thus, are easy to predict. In others, there are many possible pathwaysfor example, the introduced nitrogen-fixing legume, Myrica faya, alter successional trajectories in Hawaiian forests.[9]

The theoretical ecologist Robert Ulanowicz has used information theory tools to describe the structure of ecosystems, emphasizing mutual information (correlations) in studied systems. Drawing on this methodology and prior observations of complex ecosystems, Ulanowicz depicts approaches to determining the stress levels on ecosystems and predicting system reactions to defined types of alteration in their settings (such as increased or reduced energy flow, and eutrophication.[34]

Ecosystem ecology studies “the flow of energy and materials through organisms and the physical environment”. It seeks to understand the processes which govern the stocks of material and energy in ecosystems, and the flow of matter and energy through them. The study of ecosystems can cover 10 orders of magnitude, from the surface layers of rocks to the surface of the planet.[35]

There is no single definition of what constitutes an ecosystem.[36] German ecologist Ernst-Detlef Schulze and coauthors defined an ecosystem as an area which is “uniform regarding the biological turnover, and contains all the fluxes above and below the ground area under consideration.” They explicitly reject Gene Likens’ use of entire river catchments as “too wide a demarcation” to be a single ecosystem, given the level of heterogeneity within such an area.[37] Other authors have suggested that an ecosystem can encompass a much larger area, even the whole planet.[6] Schulze and coauthors also rejected the idea that a single rotting log could be studied as an ecosystem because the size of the flows between the log and its surroundings are too large, relative to the proportion cycles within the log.[37] Philosopher of science Mark Sagoff considers the failure to define “the kind of object it studies” to be an obstacle to the development of theory in ecosystem ecology.[36]

Ecosystems can be studied through a variety of approachestheoretical studies, studies monitoring specific ecosystems over long periods of time, those that look at differences between ecosystems to elucidate how they work and direct manipulative experimentation.[38] Studies can be carried out at a variety of scales, from microcosms and mesocosms which serve as simplified representations of ecosystems, through whole-ecosystem studies.[39] American ecologist Stephen R. Carpenter has argued that microcosm experiments can be “irrelevant and diversionary” if they are not carried out in conjunction with field studies carried out at the ecosystem scale, because microcosm experiments often fail to accurately predict ecosystem-level dynamics.[40]

The Hubbard Brook Ecosystem Study, established in the White Mountains, New Hampshire in 1963, was the first successful attempt to study an entire watershed as an ecosystem. The study used stream chemistry as a means of monitoring ecosystem properties, and developed a detailed biogeochemical model of the ecosystem.[41] Long-term research at the site led to the discovery of acid rain in North America in 1972, and was able to document the consequent depletion of soil cations (especially calcium) over the next several decades.[42]

Classifying ecosystems into ecologically homogeneous units is an important step towards effective ecosystem management.[43] A variety of systems exist, based on vegetation cover, remote sensing, and bioclimatic classification systems.[43] American geographer Robert Bailey defines a hierarchy of ecosystem units ranging from microecosystems (individual homogeneous sites, on the order of 10 square kilometres (4sqmi) in area), through mesoecosystems (landscape mosaics, on the order of 1,000 square kilometres (400sqmi)) to macroecosystems (ecoregions, on the order of 100,000 square kilometres (40,000sqmi)).[44]

Bailey outlined five different methods for identifying ecosystems: gestalt (“a whole that is not derived through considerable of its parts”), in which regions are recognized and boundaries drawn intuitively; a map overlay system where different layers like geology, landforms and soil types are overlain to identify ecosystems; multivariate clustering of site attributes; digital image processing of remotely sensed data grouping areas based on their appearance or other spectral properties; or by a “controlling factors method” where a subset of factors (like soils, climate, vegetation physiognomy or the distribution of plant or animal species) are selected from a large array of possible ones are used to delineate ecosystems.[45] In contrast with Bailey’s methodology, Puerto Rico ecologist Ariel Lugo and coauthors identified ten characteristics of an effective classification system: that it be based on georeferenced, quantitative data; that it should minimize subjectivity and explicitly identify criteria and assumptions; that it should be structured around the factors that drive ecosystem processes; that it should reflect the hierarchical nature of ecosystems; that it should be flexible enough to conform to the various scales at which ecosystem management operates; that it should be tied to reliable measures of climate so that it can “anticipat[e] global climate change; that it be applicable worldwide; that it should be validated against independent data; that it take into account the sometimes complex relationship between climate, vegetation and ecosystem functioning; and that it should be able to adapt and improve as new data become available”.[43]

As human populations and per capita consumption grow, so do the resource demands imposed on ecosystems and the impacts of the human ecological footprint. Natural resources are not invulnerable and infinitely available. The environmental impacts of anthropogenic actions, which are processes or materials derived from human activities, are becoming more apparentair and water quality are increasingly compromised, oceans are being overfished, pests and diseases are extending beyond their historical boundaries, and deforestation is exacerbating flooding downstream. It has been reported that approximately 4050% of Earth’s ice-free land surface has been heavily transformed or degraded by anthropogenic activities, 66% of marine fisheries are either overexploited or at their limit, atmospheric CO2 has increased more than 30% since the advent of industrialization, and nearly 25% of Earth’s bird species have gone extinct in the last two thousand years.[46] Society is increasingly becoming aware that ecosystem services are not only limited, but also that they are threatened by human activities. The need to better consider long-term ecosystem health and its role in enabling human habitation and economic activity is urgent. To help inform decision-makers, many ecosystem services are being assigned economic values, often based on the cost of replacement with anthropogenic alternatives. The ongoing challenge of prescribing economic value to nature, for example through biodiversity banking, is prompting transdisciplinary shifts in how we recognize and manage the environment, social responsibility, business opportunities, and our future as a species.

See the article here:

Ecosystem – Wikipedia

Ecosystem – Wikipedia

This article is about natural ecosystems. For the term used in man-made systems, see Digital ecosystem.

An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment (things like air, water and mineral soil), interacting as a system.[2] These biotic and abiotic components are regarded as linked together through nutrient cycles and energy flows.[3] As ecosystems are defined by the network of interactions among organisms, and between organisms and their environment,[4] they can be of any size but usually encompass specific, limited spaces[5] (although some scientists say that the entire planet is an ecosystem).[6] Energy, water, nitrogen and soil minerals are other essential abiotic components of an ecosystem. The energy that flows through ecosystems is obtained primarily from the sun. It generally enters the system through photosynthesis, a process that also captures carbon dioxide from the atmosphere. By feeding on plants and on one another, animals play an important role in the movement of matter and energy through the system. They also influence the quantity of plant and microbial biomass present. By breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and other microbes.[7]

Ecosystems are controlled both by external and internal factors. External factors such as climate, the parent material that forms the soil, and topography control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem.[8] Other external factors include time and potential biota. Ecosystems are dynamic entitiesinvariably, they are subject to periodic disturbances and are in the process of recovering from some past disturbance.[9] Ecosystems in similar environments that are located in different parts of the world can have very different characteristics simply because they contain different species.[8] The introduction of non-native species can cause substantial shifts in ecosystem function. Internal factors not only control ecosystem processes but are also controlled by them and are often subject to feedback loops.[8] While the resource inputs are generally controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading.[8] Other internal factors include disturbance, succession and the types of species present. Although humans exist and operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.[8]

Biodiversity affects ecosystem function, as do the processes of disturbance and succession. Ecosystems provide a variety of goods and services upon which people depend; the principles of ecosystem management suggest that rather than managing individual species, natural resources should be managed at the level of the ecosystem itself. Classifying ecosystems into ecologically homogeneous units is an important step towards effective ecosystem management, but there is no single, agreed-upon way to do this.

The term “ecosystem” was first used in 1935 in a publication by British ecologist Arthur Tansley.[fn 1][10] Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment.[11] He later refined the term, describing it as “The whole system, … including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment”.[12] Tansley regarded ecosystems not simply as natural units, but as mental isolates.[12] Tansley later[13] defined the spatial extent of ecosystems using the term ecotope.

G. Evelyn Hutchinson, a pioneering limnologist who was a contemporary of Tansley’s, combined Charles Elton’s ideas about trophic ecology with those of Russian geochemist Vladimir Vernadsky to suggest that mineral nutrient availability in a lake limited algal production which would, in turn, limit the abundance of animals that feed on algae. Raymond Lindeman took these ideas one step further to suggest that the flow of energy through a lake was the primary driver of the ecosystem. Hutchinson’s students, brothers Howard T. Odum and Eugene P. Odum, further developed a “systems approach” to the study of ecosystems, allowing them to study the flow of energy and material through ecological systems.[11]

Energy and carbon enter ecosystems through photosynthesis, are incorporated into living tissue, transferred to other organisms that feed on the living and dead plant matter, and eventually released through respiration.[14] Most mineral nutrients, on the other hand, are recycled within ecosystems.[15]

Ecosystems are controlled both by external and internal factors. External factors, also called state factors, control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem. The most important of these is climate.[8] Climate determines the biome in which the ecosystem is embedded. Rainfall patterns and temperature seasonality determine the amount of water available to the ecosystem and the supply of energy available (by influencing photosynthesis).[8] Parent material, the underlying geological material that gives rise to soils, determines the nature of the soils present, and influences the supply of mineral nutrients. Topography also controls ecosystem processes by affecting things like microclimate, soil development and the movement of water through a system. This may be the difference between the ecosystem present in wetland situated in a small depression on the landscape, and one present on an adjacent steep hillside.[8]

Other external factors that play an important role in ecosystem functioning include time and potential biota. Ecosystems are dynamic entitiesinvariably, they are subject to periodic disturbances and are in the process of recovering from some past disturbance.[9] Time plays a role in the development of soil from bare rock and the recovery of a community from disturbance.[8] Similarly, the set of organisms that can potentially be present in an area can also have a major impact on ecosystems. Ecosystems in similar environments that are located in different parts of the world can end up doing things very differently simply because they have different pools of species present.[8] The introduction of non-native species can cause substantial shifts in ecosystem function.

Unlike external factors, internal factors in ecosystems not only control ecosystem processes, but are also controlled by them. Consequently, they are often subject to feedback loops.[8] While the resource inputs are generally controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading.[8] Other factors like disturbance, succession or the types of species present are also internal factors. Human activities are important in almost all ecosystems. Although humans exist and operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.[8]

Primary production is the production of organic matter from inorganic carbon sources. Overwhelmingly, this occurs through photosynthesis. The energy incorporated through this process supports life on earth, while the carbon makes up much of the organic matter in living and dead biomass, soil carbon and fossil fuels. It also drives the carbon cycle, which influences global climate via the greenhouse effect.

Through the process of photosynthesis, plants capture energy from light and use it to combine carbon dioxide and water to produce carbohydrates and oxygen. The photosynthesis carried out by all the plants in an ecosystem is called the gross primary production (GPP).[16] About 4860% of the GPP is consumed in plant respiration. The remainder, that portion of GPP that is not used up by respiration, is known as the net primary production (NPP).[14] Total photosynthesis is limited by a range of environmental factors. These include the amount of light available, the amount of leaf area a plant has to capture light (shading by other plants is a major limitation of photosynthesis), rate at which carbon dioxide can be supplied to the chloroplasts to support photosynthesis, the availability of water, and the availability of suitable temperatures for carrying out photosynthesis.[16]

The carbon and energy incorporated into plant tissues (net primary production) is either consumed by animals while the plant is alive, or it remains uneaten when the plant tissue dies and becomes detritus. In terrestrial ecosystems, roughly 90% of the NPP ends up being broken down by decomposers. The remainder is either consumed by animals while still alive and enters the plant-based trophic system, or it is consumed after it has died, and enters the detritus-based trophic system. In aquatic systems, the proportion of plant biomass that gets consumed by herbivores is much higher.[18] In trophic systems photosynthetic organisms are the primary producers. The organisms that consume their tissues are called primary consumers or secondary producersherbivores. Organisms which feed on microbes (bacteria and fungi) are termed microbivores. Animals that feed on primary consumerscarnivoresare secondary consumers. Each of these constitutes a trophic level.[18] The sequence of consumptionfrom plant to herbivore, to carnivoreforms a food chain. Real systems are much more complex than thisorganisms will generally feed on more than one form of food, and may feed at more than one trophic level. Carnivores may capture some prey which are part of a plant-based trophic system and others that are part of a detritus-based trophic system (a bird that feeds both on herbivorous grasshoppers and earthworms, which consume detritus). Real systems, with all these complexities, form food webs rather than food chains.[18]

The carbon and nutrients in dead organic matter are broken down by a group of processes known as decomposition. This releases nutrients that can then be re-used for plant and microbial production, and returns carbon dioxide to the atmosphere (or water) where it can be used for photosynthesis. In the absence of decomposition, dead organic matter would accumulate in an ecosystem and nutrients and atmospheric carbon dioxide would be depleted.[19] Approximately 90% of terrestrial NPP goes directly from plant to decomposer.[18]

Decomposition processes can be separated into three categoriesleaching, fragmentation and chemical alteration of dead material. As water moves through dead organic matter, it dissolves and carries with it the water-soluble components. These are then taken up by organisms in the soil, react with mineral soil, or are transported beyond the confines of the ecosystem (and are considered lost to it).[19] Newly shed leaves and newly dead animals have high concentrations of water-soluble components, and include sugars, amino acids and mineral nutrients. Leaching is more important in wet environments, and much less important in dry ones.[19]

Fragmentation processes break organic material into smaller pieces, exposing new surfaces for colonization by microbes. Freshly shed leaf litter may be inaccessible due to an outer layer of cuticle or bark, and cell contents are protected by a cell wall. Newly dead animals may be covered by an exoskeleton. Fragmentation processes, which break through these protective layers, accelerate the rate of microbial decomposition.[19] Animals fragment detritus as they hunt for food, as does passage through the gut. Freeze-thaw cycles and cycles of wetting and drying also fragment dead material.[19]

The chemical alteration of dead organic matter is primarily achieved through bacterial and fungal action. Fungal hyphae produce enzymes which can break through the tough outer structures surrounding dead plant material. They also produce enzymes which break down lignin, which allows them access to both cell contents and to the nitrogen in the lignin. Fungi can transfer carbon and nitrogen through their hyphal networks and thus, unlike bacteria, are not dependent solely on locally available resources.[19]

Decomposition rates vary among ecosystems. The rate of decomposition is governed by three sets of factorsthe physical environment (temperature, moisture and soil properties), the quantity and quality of the dead material available to decomposers, and the nature of the microbial community itself.[20] Temperature controls the rate of microbial respiration; the higher the temperature, the faster microbial decomposition occurs. It also affects soil moisture, which slows microbial growth and reduces leaching. Freeze-thaw cycles also affect decompositionfreezing temperatures kill soil microorganisms, which allows leaching to play a more important role in moving nutrients around. This can be especially important as the soil thaws in the Spring, creating a pulse of nutrients which become available.[20]

Decomposition rates are low under very wet or very dry conditions. Decomposition rates are highest in wet, moist conditions with adequate levels of oxygen. Wet soils tend to become deficient in oxygen (this is especially true in wetlands), which slows microbial growth. In dry soils, decomposition slows as well, but bacteria continue to grow (albeit at a slower rate) even after soils become too dry to support plant growth. When the rains return and soils become wet, the osmotic gradient between the bacterial cells and the soil water causes the cells to gain water quickly. Under these conditions, many bacterial cells burst, releasing a pulse of nutrients.[20] Decomposition rates also tend to be slower in acidic soils.[20] Soils which are rich in clay minerals tend to have lower decomposition rates, and thus, higher levels of organic matter.[20] The smaller particles of clay result in a larger surface area that can hold water. The higher the water content of a soil, the lower the oxygen content[21] and consequently, the lower the rate of decomposition. Clay minerals also bind particles of organic material to their surface, making them less accessibly to microbes.[20] Soil disturbance like tilling increase decomposition by increasing the amount of oxygen in the soil and by exposing new organic matter to soil microbes.[20]

The quality and quantity of the material available to decomposers is another major factor that influences the rate of decomposition. Substances like sugars and amino acids decompose readily and are considered labile. Cellulose and hemicellulose, which are broken down more slowly, are “moderately labile”. Compounds which are more resistant to decay, like lignin or cutin, are considered recalcitrant.[20] Litter with a higher proportion of labile compounds decomposes much more rapidly than does litter with a higher proportion of recalcitrant material. Consequently, dead animals decompose more rapidly than dead leaves, which themselves decompose more rapidly than fallen branches.[20] As organic material in the soil ages, its quality decreases. The more labile compounds decompose quickly, leaving an increasing proportion of recalcitrant material. Microbial cell walls also contain recalcitrant materials like chitin, and these also accumulate as the microbes die, further reducing the quality of older soil organic matter.[20]

Ecosystems continually exchange energy and carbon with the wider environment; mineral nutrients, on the other hand, are mostly cycled back and forth between plants, animals, microbes and the soil. Most nitrogen enters ecosystems through biological nitrogen fixation, is deposited through precipitation, dust, gases or is applied as fertilizer.[15] Since most terrestrial ecosystems are nitrogen-limited, nitrogen cycling is an important control on ecosystem production.[15]

Until modern times, nitrogen fixation was the major source of nitrogen for ecosystems. Nitrogen fixing bacteria either live symbiotically with plants, or live freely in the soil. The energetic cost is high for plants which support nitrogen-fixing symbiontsas much as 25% of GPP when measured in controlled conditions. Many members of the legume plant family support nitrogen-fixing symbionts. Some cyanobacteria are also capable of nitrogen fixation. These are phototrophs, which carry out photosynthesis. Like other nitrogen-fixing bacteria, they can either be free-living or have symbiotic relationships with plants.[15] Other sources of nitrogen include acid deposition produced through the combustion of fossil fuels, ammonia gas which evaporates from agricultural fields which have had fertilizers applied to them, and dust.[15] Anthropogenic nitrogen inputs account for about 80% of all nitrogen fluxes in ecosystems.[15]

When plant tissues are shed or are eaten, the nitrogen in those tissues becomes available to animals and microbes. Microbial decomposition releases nitrogen compounds from dead organic matter in the soil, where plants, fungi and bacteria compete for it. Some soil bacteria use organic nitrogen-containing compounds as a source of carbon, and release ammonium ions into the soil. This process is known as nitrogen mineralization. Others convert ammonium to nitrite and nitrate ions, a process known as nitrification. Nitric oxide and nitrous oxide are also produced during nitrification.[15] Under nitrogen-rich and oxygen-poor conditions, nitrates and nitrites are converted to nitrogen gas, a process known as denitrification.[15]

Other important nutrients include phosphorus, sulfur, calcium, potassium, magnesium and manganese.[22] Phosphorus enters ecosystems through weathering. As ecosystems age this supply diminishes, making phosphorus-limitation more common in older landscapes (especially in the tropics).[22] Calcium and sulfur are also produced by weathering, but acid deposition is an important source of sulfur in many ecosystems. Although magnesium and manganese are produced by weathering, exchanges between soil organic matter and living cells account for a significant portion of ecosystem fluxes. Potassium is primarily cycled between living cells and soil organic matter.[22]

Ecosystem processes are broad generalizations that actually take place through the actions of individual organisms. The nature of the organismsthe species, functional groups and trophic levels to which they belongdictates the sorts of actions these individuals are capable of carrying out, and the relative efficiency with which they do so. Thus, ecosystem processes are driven by the number of species in an ecosystem, the exact nature of each individual species, and the relative abundance organisms within these species.[24] Biodiversity plays an important role in ecosystem functioning.[25]

Ecological theory suggests that in order to coexist, species must have some level of limiting similaritythey must be different from one another in some fundamental way, otherwise one species would competitively exclude the other.[26] Despite this, the cumulative effect of additional species in an ecosystem is not linearadditional species may enhance nitrogen retention, for example, but beyond some level of species richness, additional species may have little additive effect.[24] The addition (or loss) of species which are ecologically similar to those already present in an ecosystem tends to only have a small effect on ecosystem function. Ecologically distinct species, on the other hand, have a much larger effect. Similarly, dominant species have a large impact on ecosystem function, while rare species tend to have a small effect. Keystone species tend to have an effect on ecosystem function that is disproportionate to their abundance in an ecosystem.[24]

Ecosystems provide a variety of goods and services upon which people depend.[27] Ecosystem goods include the “tangible, material products”[28] of ecosystem processesfood, construction material, medicinal plantsin addition to less tangible items like tourism and recreation, and genes from wild plants and animals that can be used to improve domestic species.[27] Ecosystem services, on the other hand, are generally “improvements in the condition or location of things of value”.[28] These include things like the maintenance of hydrological cycles, cleaning air and water, the maintenance of oxygen in the atmosphere, crop pollination and even things like beauty, inspiration and opportunities for research.[27] While ecosystem goods have traditionally been recognized as being the basis for things of economic value, ecosystem services tend to be taken for granted.[28] While Gretchen Daily’s original definition distinguished between ecosystem goods and ecosystem services, Robert Costanza and colleagues’ later work and that of the Millennium Ecosystem Assessment lumped all of these together as ecosystem services.[28][29]

When natural resource management is applied to whole ecosystems, rather than single species, it is termed ecosystem management.[30] A variety of definitions exist: F. Stuart Chapin and coauthors define it as “the application of ecological science to resource management to promote long-term sustainability of ecosystems and the delivery of essential ecosystem goods and services”,[31] while Norman Christensen and coauthors defined it as “management driven by explicit goals, executed by policies, protocols, and practices, and made adaptable by monitoring and research based on our best understanding of the ecological interactions and processes necessary to sustain ecosystem structure and function”[27] and Peter Brussard and colleagues defined it as “managing areas at various scales in such a way that ecosystem services and biological resources are preserved while appropriate human use and options for livelihood are sustained”.[32]

Although definitions of ecosystem management abound, there is a common set of principles which underlie these definitions.[31] A fundamental principle is the long-term sustainability of the production of goods and services by the ecosystem;[31] “intergenerational sustainability [is] a precondition for management, not an afterthought”.[27] It also requires clear goals with respect to future trajectories and behaviors of the system being managed. Other important requirements include a sound ecological understanding of the system, including connectedness, ecological dynamics and the context in which the system is embedded. Other important principles include an understanding of the role of humans as components of the ecosystems and the use of adaptive management.[27] While ecosystem management can be used as part of a plan for wilderness conservation, it can also be used in intensively managed ecosystems[27] (see, for example, agroecosystem and close to nature forestry).

Ecosystems are dynamic entitiesinvariably, they are subject to periodic disturbances and are in the process of recovering from some past disturbance.[9] When an ecosystem is subject to some sort of perturbation, it responds by moving away from its initial state. The tendency of a system to remain close to its equilibrium state, despite that disturbance, is termed its resistance. On the other hand, the speed with which it returns to its initial state after disturbance is called its resilience.[9]

From one year to another, ecosystems experience variation in their biotic and abiotic environments. A drought, an especially cold winter and a pest outbreak all constitute short-term variability in environmental conditions. Animal populations vary from year to year, building up during resource-rich periods and crashing as they overshoot their food supply. These changes play out in changes in NPP, decomposition rates, and other ecosystem processes.[9] Longer-term changes also shape ecosystem processesthe forests of eastern North America still show legacies of cultivation which ceased 200 years ago, while methane production in eastern Siberian lakes is controlled by organic matter which accumulated during the Pleistocene.[9]

Disturbance also plays an important role in ecological processes. F. Stuart Chapin and coauthors define disturbance as “a relatively discrete event in time and space that alters the structure of populations, communities and ecosystems and causes changes in resources availability or the physical environment”.[33] This can range from tree falls and insect outbreaks to hurricanes and wildfires to volcanic eruptions and can cause large changes in plant, animal and microbe populations, as well soil organic matter content.[9] Disturbance is followed by succession, a “directional change in ecosystem structure and functioning resulting from biotically driven changes in resources supply.”[33]

The frequency and severity of disturbance determines the way it impacts ecosystem function. Major disturbance like a volcanic eruption or glacial advance and retreat leave behind soils that lack plants, animals or organic matter. Ecosystems that experience disturbances that undergo primary succession. Less severe disturbance like forest fires, hurricanes or cultivation result in secondary succession.[9] More severe disturbance and more frequent disturbance result in longer recovery times. Ecosystems recover more quickly from less severe disturbance events.[9]

The early stages of primary succession are dominated by species with small propagules (seed and spores) which can be dispersed long distances. The early colonizersoften algae, cyanobacteria and lichensstabilize the substrate. Nitrogen supplies are limited in new soils, and nitrogen-fixing species tend to play an important role early in primary succession. Unlike in primary succession, the species that dominate secondary succession, are usually present from the start of the process, often in the soil seed bank. In some systems the successional pathways are fairly consistent, and thus, are easy to predict. In others, there are many possible pathwaysfor example, the introduced nitrogen-fixing legume, Myrica faya, alter successional trajectories in Hawaiian forests.[9]

The theoretical ecologist Robert Ulanowicz has used information theory tools to describe the structure of ecosystems, emphasizing mutual information (correlations) in studied systems. Drawing on this methodology and prior observations of complex ecosystems, Ulanowicz depicts approaches to determining the stress levels on ecosystems and predicting system reactions to defined types of alteration in their settings (such as increased or reduced energy flow, and eutrophication.[34]

Ecosystem ecology studies “the flow of energy and materials through organisms and the physical environment”. It seeks to understand the processes which govern the stocks of material and energy in ecosystems, and the flow of matter and energy through them. The study of ecosystems can cover 10 orders of magnitude, from the surface layers of rocks to the surface of the planet.[35]

There is no single definition of what constitutes an ecosystem.[36] German ecologist Ernst-Detlef Schulze and coauthors defined an ecosystem as an area which is “uniform regarding the biological turnover, and contains all the fluxes above and below the ground area under consideration.” They explicitly reject Gene Likens’ use of entire river catchments as “too wide a demarcation” to be a single ecosystem, given the level of heterogeneity within such an area.[37] Other authors have suggested that an ecosystem can encompass a much larger area, even the whole planet.[6] Schulze and coauthors also rejected the idea that a single rotting log could be studied as an ecosystem because the size of the flows between the log and its surroundings are too large, relative to the proportion cycles within the log.[37] Philosopher of science Mark Sagoff considers the failure to define “the kind of object it studies” to be an obstacle to the development of theory in ecosystem ecology.[36]

Ecosystems can be studied through a variety of approachestheoretical studies, studies monitoring specific ecosystems over long periods of time, those that look at differences between ecosystems to elucidate how they work and direct manipulative experimentation.[38] Studies can be carried out at a variety of scales, from microcosms and mesocosms which serve as simplified representations of ecosystems, through whole-ecosystem studies.[39] American ecologist Stephen R. Carpenter has argued that microcosm experiments can be “irrelevant and diversionary” if they are not carried out in conjunction with field studies carried out at the ecosystem scale, because microcosm experiments often fail to accurately predict ecosystem-level dynamics.[40]

The Hubbard Brook Ecosystem Study, established in the White Mountains, New Hampshire in 1963, was the first successful attempt to study an entire watershed as an ecosystem. The study used stream chemistry as a means of monitoring ecosystem properties, and developed a detailed biogeochemical model of the ecosystem.[41] Long-term research at the site led to the discovery of acid rain in North America in 1972, and was able to document the consequent depletion of soil cations (especially calcium) over the next several decades.[42]

Classifying ecosystems into ecologically homogeneous units is an important step towards effective ecosystem management.[43] A variety of systems exist, based on vegetation cover, remote sensing, and bioclimatic classification systems.[43] American geographer Robert Bailey defines a hierarchy of ecosystem units ranging from microecosystems (individual homogeneous sites, on the order of 10 square kilometres (4sqmi) in area), through mesoecosystems (landscape mosaics, on the order of 1,000 square kilometres (400sqmi)) to macroecosystems (ecoregions, on the order of 100,000 square kilometres (40,000sqmi)).[44]

Bailey outlined five different methods for identifying ecosystems: gestalt (“a whole that is not derived through considerable of its parts”), in which regions are recognized and boundaries drawn intuitively; a map overlay system where different layers like geology, landforms and soil types are overlain to identify ecosystems; multivariate clustering of site attributes; digital image processing of remotely sensed data grouping areas based on their appearance or other spectral properties; or by a “controlling factors method” where a subset of factors (like soils, climate, vegetation physiognomy or the distribution of plant or animal species) are selected from a large array of possible ones are used to delineate ecosystems.[45] In contrast with Bailey’s methodology, Puerto Rico ecologist Ariel Lugo and coauthors identified ten characteristics of an effective classification system: that it be based on georeferenced, quantitative data; that it should minimize subjectivity and explicitly identify criteria and assumptions; that it should be structured around the factors that drive ecosystem processes; that it should reflect the hierarchical nature of ecosystems; that it should be flexible enough to conform to the various scales at which ecosystem management operates; that it should be tied to reliable measures of climate so that it can “anticipat[e] global climate change; that it be applicable worldwide; that it should be validated against independent data; that it take into account the sometimes complex relationship between climate, vegetation and ecosystem functioning; and that it should be able to adapt and improve as new data become available”.[43]

As human populations and per capita consumption grow, so do the resource demands imposed on ecosystems and the impacts of the human ecological footprint. Natural resources are not invulnerable and infinitely available. The environmental impacts of anthropogenic actions, which are processes or materials derived from human activities, are becoming more apparentair and water quality are increasingly compromised, oceans are being overfished, pests and diseases are extending beyond their historical boundaries, and deforestation is exacerbating flooding downstream. It has been reported that approximately 4050% of Earth’s ice-free land surface has been heavily transformed or degraded by anthropogenic activities, 66% of marine fisheries are either overexploited or at their limit, atmospheric CO2 has increased more than 30% since the advent of industrialization, and nearly 25% of Earth’s bird species have gone extinct in the last two thousand years.[46] Society is increasingly becoming aware that ecosystem services are not only limited, but also that they are threatened by human activities. The need to better consider long-term ecosystem health and its role in enabling human habitation and economic activity is urgent. To help inform decision-makers, many ecosystem services are being assigned economic values, often based on the cost of replacement with anthropogenic alternatives. The ongoing challenge of prescribing economic value to nature, for example through biodiversity banking, is prompting transdisciplinary shifts in how we recognize and manage the environment, social responsibility, business opportunities, and our future as a species.

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Ecosystem – Wikipedia