Ecosystem

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Ecosystem

Top: Coral reef ecosystems are highly productive marine systems, bottom: Temperate rainforest on the Olympic Peninsula in Washington state.

 

An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the system through photosynthesis and is incorporated into plant tissue. 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.

Ecosystems are controlled by external and internal factors. External factors such as climate, parent material which forms the soil and topography, control the overall structure of an ecosystem but are not themselves influenced by the ecosystem. Unlike external factors, internal factors are controlled, for example, decomposition, root competition, shading, disturbance, succession, and the types of species present.

Ecosystems are dynamic entities—they are subject to periodic disturbances and are in the process of recovering from some past disturbance. 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. Internal factors not only control ecosystem processes but are also controlled by them and are often subject to feedback loops.

Resource inputs are generally controlled by external processes like climate and parent material. Resource availability within the ecosystem is controlled by internal factors like decomposition, root competition or shading. Although humans operate within ecosystems, their cumulative effects are large enough to influence external factors like climate.

Biodiversity affects ecosystem functioning, as do the processes of disturbance and succession. Ecosystems provide a variety of goods and services upon which people depend.

History

The term ecosystem was first used in 1935 in a publication by British ecologist Arthur Tansley. Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment. 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". Tansley regarded ecosystems not simply as natural units, but as "mental isolates". Tansley later defined the spatial extent of ecosystems using the term ecotope.

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.

Processes

Rainforest ecosystems are rich in biodiversity. This is the Gambia River in Senegal's Niokolo-Koba National Park.

 

Flora of Baja California Desert, Cataviña region, Mexico

 

Biomes of the world

 

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. Climate determines the biome in which the ecosystem is embedded. Rainfall patterns and seasonal temperatures influence photosynthesis and thereby determine the amount of water and energy available to the ecosystem.

Parent material determines the nature of the soil in an ecosystem, 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. For example, ecosystems can be quite different if situated in a small depression on the landscape, versus one present on an adjacent steep hillside.

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 significantly affect 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. 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. 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. Other factors like disturbance, succession or the types of species present are also internal factors.

Primary production

Global oceanic and terrestrial phototroph abundance, from September 1997 to August 2000. As an estimate of autotroph biomass, it is only a rough indicator of primary production potential and not an actual estimate of it.

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). About half 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). 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.

Energy flow

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.

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. In trophic systems photosynthetic organisms are the primary producers. The organisms that consume their tissues are called primary consumers or secondary producers—herbivores. Organisms which feed on microbes (bacteria and fungi) are termed microbivores. Animals that feed on primary consumers—carnivores—are secondary consumers. Each of these constitutes a trophic level.

The sequence of consumption—from plant to herbivore, to carnivore—forms a food chain. Real systems are much more complex than this—organisms 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 is 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. The food chain usually consists of five levels of consumption which are producers, primary consumers, secondary consumers, tertiary consumers, and decomposers.

Decomposition

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, the dead organic matter would accumulate in an ecosystem, and nutrients and atmospheric carbon dioxide would be depleted. Approximately 90% of terrestrial net primary production goes directly from plant to decomposer.

Decomposition processes can be separated into three categories—leaching, 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). 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.

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. 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.

The chemical alteration of the dead organic matter is primarily achieved through bacterial and fungal action. Fungal hyphae produces enzymes that 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 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.

Decomposition rates vary among ecosystems. The rate of decomposition is governed by three sets of factors—the 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. Temperature controls the rate of microbial respiration; the higher the temperature, the faster the microbial decomposition occurs. It also affects soil moisture, which slows microbial growth and reduces leaching. Freeze-thaw cycles also affect decomposition—freezing 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.

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.

Nutrient cycling

Biological nitrogen cycling

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.

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

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 that support nitrogen-fixing symbionts—as 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. 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. Anthropogenic nitrogen inputs account for about 80% of all nitrogen fluxes in ecosystems.

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. Under nitrogen-rich and oxygen-poor conditions, nitrates and nitrites are converted to nitrogen gas, a process known as denitrification.

Other important nutrients include phosphorus, sulfur, calcium, potassium, magnesium and manganese. Phosphorus enters ecosystems through weathering. As ecosystems age this supply diminishes, making phosphorus-limitation more common in older landscapes (especially in the tropics). 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.

Function and biodiversity

Loch Lomond in Scotland forms a relatively isolated ecosystem. The fish community of this lake has remained stable over a long period until a number of introductions in the 1970s restructured its food web.

 

Spiny forest at Ifaty, Madagascar, featuring various Adansonia (baobab) species, Alluaudia procera (Madagascar ocotillo) and other vegetation.

 

Biodiversity plays an important role in ecosystem functioning. 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. Ecosystem processes are broad generalizations that actually take place through the actions of individual organisms. The nature of the organisms—the species, functional groups and trophic levels to which they belong—dictates 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 similarity—they must be different from one another in some fundamental way, otherwise one species would competitively exclude the other. Despite this, the cumulative effect of additional species in an ecosystem is not linear—additional species may enhance nitrogen retention, for example, but beyond some level of species richness, additional species may have little additive effect.

The addition (or loss) of species that 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 effect 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. Similarly, an ecosystem engineer is any organism that creates, significantly modifies, maintains or destroys a habitat.

Dynamics

Ecosystems are dynamic entities. They are subject to periodic disturbances and are in the process of recovering from some past disturbance. When a perturbation occurs, an ecosystem 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 it's resilience. Time plays a role in the development of soil from bare rock and the recovery of a community from disturbance.

From one year to another, ecosystems experience variation in their biotic and abiotic environments. A drought, a colder than usual winter, and a pest outbreak all are 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. Longer-term changes also shape ecosystem processes—the 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.

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". 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 as soil organic matter content. Disturbance is followed by succession, a "directional change in ecosystem structure and functioning resulting from biotically driven changes in resources supply."

The frequency and severity of disturbance determine the way it affects ecosystem function. A 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. A less severe disturbance like forest fires, hurricanes or cultivation result in secondary succession and a faster recovery. More severe disturbance and more frequent disturbance result in longer recovery times.

A freshwater lake in Gran Canaria, an island of the Canary Islands.

Clear boundaries make lakes convenient to study using an ecosystem approach.

Ecosystem ecology

A hydrothermal vent is an ecosystem on the ocean floor. (The scale bar is 1 m.)

 

Ecosystem ecology studies the processes and dynamics of ecosystems, and the way the flow of matter and energy through them structures natural systems. The study of ecosystems can cover 10 orders of magnitude, from the surface layers of rocks to the surface of the planet.

There is no single definition of what constitutes an ecosystem. 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. Other authors have suggested that an ecosystem can encompass a much larger area, even the whole planet. 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. 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.

Ecosystems can be studied through a variety of approaches—theoretical 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. Studies can be carried out at a variety of scales, ranging from whole-ecosystem studies to studying microcosms or mesocosms (simplified representations of ecosystems). 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 done at the ecosystem scale. Microcosm experiments often fail to accurately predict ecosystem-level dynamics.

The Hubbard Brook Ecosystem Study started in 1963 to study the White Mountains in New Hampshire. It 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. Long-term research at the site led to the discovery of acid rain in North America in 1972. Researchers documented the depletion of soil cations (especially calcium) over the next several decades.

Human activities

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.

Ecosystem goods and services

The High Peaks Wilderness Area in the 6,000,000-acre (2,400,000 ha) Adirondack Park is an example of a diverse ecosystem.

Ecosystems provide a variety of goods and services upon which people depend. Ecosystem goods include the "tangible, material products" of ecosystem processes such as food, construction material, medicinal plants. 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.

Ecosystem services, on the other hand, are generally "improvements in the condition or location of things of value". 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. While material from the ecosystem had traditionally been recognized as being the basis for things of economic value, ecosystem services tend to be taken for granted.

Ecosystem management

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

While ecosystem management can be used as part of a plan for wilderness conservation, it can also be used in intensively managed ecosystems.

Threats caused by humans

As human population and per capita consumption grow, so do the resource demands imposed on ecosystems and the effects 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, the warming of oceans, and building on coastal areas.

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.

Ecosystem health

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Ecosystem_health

Ecosystem health is a metaphor used to describe the condition of an ecosystem. Ecosystem condition can vary as a result of fire, flooding, drought, extinctions, invasive species, climate change, mining, overexploitation in fishing, farming or logging, chemical spills, and a host of other reasons. There is no universally accepted benchmark for a healthy ecosystem, rather the apparent health status of an ecosystem can vary depending upon which health metrics are employed in judging it and which societal aspirations are driving the assessment. Advocates of the health metaphor argue for its simplicity as a communication tool. "Policy-makers and the public need simple, understandable concepts like health." Critics worry that ecosystem health, a "value-laden construct", is often "passed off as science to unsuspecting policy makers and the public."

History of the concept

The health metaphor applied to the environment has been in use at least since the early 1800s and the great American conservationist Aldo Leopold (1887–1948) spoke metaphorically of land health, land sickness, mutilation, and violence when describing land use practices. The term "ecosystem management" has been in use at least since the 1950s. The term "ecosystem health" has become widespread in the ecological literature, as a general metaphor meaning something good, and as an environmental quality goal in field assessments of rivers, lakes, seas, and forests.

Recently however this metaphor has been subject of quantitative formulation using complex systems concepts such as criticality, meaning that a healthy ecosystem is in some sort of balance between adaptability (randomness) and robustness (order) . Nevertheless the universality of criticality is still under examination and is known as the Criticality Hypothesis, which states that systems in a dynamic regime shifting between order and disorder, attain the highest level of computational capabilities and achieve an optimal trade-off between robustness and flexibility. Recent results in cell and evolutionary biology, neuroscience and computer science have great interest in the criticality hypothesis, emphasizing its role as a viable candidate general law in the realm of adaptive complex systems.

Meaning

The term ecosystem health has been employed to embrace some suite of environmental goals deemed desirable. Edward Grumbine's highly cited paper "What is ecosystem management?" surveyed ecosystem management and ecosystem health literature and summarized frequently encountered goal statements:

• Conserving viable populations of native species
• Conserving ecosystem diversity
• Maintaining evolutionary and ecological processes
• Managing over long time frames to maintain evolutionary potential
• Accommodating human use and occupancy within these constraints

Grumbine describes each of these goals as a "value statement" and stresses the role of human values in setting ecosystem management goals.

It is the last goal mentioned in the survey, accommodating humans, that is most contentious. "We have observed that when groups of stakeholders work to define … visions, this leads to debate over whether to emphasize ecosystem health or human well-being … Whether the priority is ecosystems or people greatly influences stakeholders' assessment of desirable ecological and social states." and, for example, "For some, wolves are critical to ecosystem health and an essential part of nature, for others they are a symbol of government overreach threatening their livelihoods and cultural values."

Measuring ecosystem health requires extensive goal-driven environmental sampling. For example, a vision for ecosystem health of Lake Superior was developed by a public forum and a series of objectives were prepared for protection of habitat and maintenance of populations of some 70 indigenous fish species. A suite of 80 lake health indicators was developed for the Great Lakes Basin including monitoring native fish species, exotic species, water levels, phosphorus levels, toxic chemicals, phytoplankton, zooplankton, fish tissue contaminants, etc.

Some authors have attempted broad definitions of ecosystem health, such as benchmarking as healthy the historical ecosystem state "prior to the onset of anthropogenic stress." A difficulty is that the historical composition of many human-altered ecosystems is unknown or unknowable. Also, fossil and pollen records indicate that the species that occupy an ecosystem reshuffle through time, so it is difficult to identify one snapshot in time as optimum or "healthy."

A commonly cited broad definition states that a healthy ecosystem has three attributes:

1. productivity,
2. resilience, and
3. "organization" (including biodiversity).

While this captures significant ecosystem properties, a generalization is elusive as those properties do not necessarily co-vary in nature. For example, there is not necessarily a clear or consistent relationship between productivity and species richness. Similarly, the relationship between resilience and diversity is complex, and ecosystem stability may depend upon one or a few species rather than overall diversity. And some undesirable ecosystems are highly productive.

"Resilience is not desirable per se. There can be highly resilient states of ecosystems which are very undesirable from some human perspectives , such as algal-dominated coral reefs." Ecological resilience is a "capacity" that varies depending upon which properties of the ecosystem are to be studied and depending upon what kinds of disturbances are considered and how they are to be quantified. Approaches to assessing it "face high uncertainties and still require a considerable amount of empirical and theoretical research."

Other authors have sought a numerical index of ecosystem health that would permit quantitative comparisons among ecosystems and within ecosystems over time. One such system employs ratings of the three properties mentioned above: Health = system vigor x system organization x system resilience. Ecologist Glenn Suter argues that such indices employ "nonsense units," the indices have "no meaning; they cannot be predicted, so they are not applicable to most regulatory problems; they have no diagnostic power; effects of one component are eclipsed by responses of other components, and the reason for a high or low index value is unknown."

Health indicators

Health metrics are determined by stakeholder goals, which drive ecosystem definition. An ecosystem is an abstraction. "Ecosystems cannot be identified or found in nature. Instead, they must be delimited by an observer. This can be done in many different ways for the same chunk of nature, depending on the specific perspectives of interest."

Ecosystem definition determines the acceptable range of variability (reference conditions) and determines measurement variables. The latter are used as indicators of ecosystem structure and function, and can be used as indicators of "health". 

An indicator is a variable, such as a chemical or biological property, that when measured, is used to infer trends in another (unmeasured) environmental variable or cluster of unmeasured variables (the indicandum). For example, rising mortality rate of canaries in a coal mine is an indicator of rising carbon monoxide levels. Rising chlorophyll-a levels in a lake may signal eutrophication.

Ecosystem assessments employ two kinds of indicators, descriptive indicators and normative indicators. "Indicators can be used descriptively for a scientific purpose or normatively for a political purpose."

Used descriptively, high chlorophyll-a is an indicator of eutrophication, but it may also be used as an ecosystem health indicator. When used as a normative (health) indicator, it indicates a rank on a health scale, a rank that can vary widely depending on societal preferences as to what is desirable. A high chlorophyll-a level in a natural successional wetland might be viewed as healthy whereas a human-impacted wetland with the same indicator value may be judged unhealthy.

Estimation of ecosystem health has been criticized for intermingling the two types of environmental indicators. A health indicator is a normative indicator, and if conflated with descriptive indicators "implies that normative values can be measured objectively, which is certainly not true. Thus, implicit values are insinuated to the reader, a situation which has to be avoided."

It can be argued that the very act of selecting indicators of any kind is biased by the observer's perspective but separation of goals from descriptions has been advocated as a step toward transparency: "A separation of descriptive and normative indicators is essential from the perspective of the philosophy of science … Goals and values cannot be deduced directly from descriptions … a fact that is emphasized repeatedly in the literature of environmental ethics … Hence, we advise always specifying the definition of indicators and propose clearly distinguishing ecological indicators in science from policy indicators used for decision-making processes."

And integration of multiple, possibly conflicting, normative indicators into a single measure of "ecosystem health" is problematic. Using 56 indicators, "determining environmental status and assessing marine ecosystems health in an integrative way is still one of the grand challenges in marine ecosystems ecology, research and management"

Another issue with indicators is validity. Good indicators must have an independently validated high predictive value, that is high sensitivity (high probability of indicating a significant change in the indicandum) and high specificity (low probability of wrongly indicating a change). The reliability of various health metrics has been questioned and "what combination of measurements should be used to evaluate ecosystems is a matter of current scientific debate." Most attempts to identify ecological indicators have been correlative rather than derived from prospective testing of their predictive value and the selection process for many indicators has been based upon weak evidence or has been lacking in evidence.

In some cases no reliable indicators are known: "We found no examples of invertebrates successfully used in [forest] monitoring programs. Their richness and abundance ensure that they play significant roles in ecosystem function but thwart focus on a few key species." And, "Reviews of species-based monitoring approaches reveal that no single species, nor even a group of species, accurately reflects entire communities. Understanding the response of a single species may not provide reliable predictions about a group of species even when the group is comprised of a few very similar species."

Relationship to human health: the health paradox

A trade-off between human health and the "health" of nature has been termed the "health paradox" and it illuminates how human values drive perceptions of ecosystem health.

Human health has benefited by sacrificing the "health" of wild ecosystems, such as dismantling and damming of wild valleys, destruction of mosquito-bearing wetlands, diversion of water for irrigation, conversion of wilderness to farmland, timber removal, and extirpation of tigers, whales, ferrets, and wolves.

There has been an acrimonious schism among conservationists and resource managers over the question of whether to "ratchet back human domination of the biosphere" or whether to embrace it. These two perspectives have been characterized as utilitarian vs protectionist.

The utilitarian view treats human health and well-being as criteria of ecosystem health. For example, destruction of wetlands to control malaria mosquitoes "resulted in an improvement in ecosystem health." The protectionist view treats humans as an invasive species: "If there was ever a species that qualified as an invasive pest, it is Homo sapiens,"

Proponents of the utilitarian view argue that "healthy ecosystems are characterized by their capability to sustain healthy human populations," and "healthy ecosystems must be economically viable," as it is "unhealthy" ecosystems that are likely to result in increases in contamination, infectious diseases, fires, floods, crop failures and fishery collapse.

Protectionists argue that privileging of human health is a conflict of interest as humans have demolished massive numbers of ecosystems to maintain their welfare, also disease and parasitism are historically normal in pre-industrial nature. Diseases and parasites promote ecosystem functioning, driving biodiversity and productivity, and parasites may constitute a significant fraction of ecosystem biomass.

The very choice of the word "health" applied to ecology has been questioned as lacking in neutrality in a BioScience article on responsible use of scientific language: "Some conservationists fear that these terms could endorse human domination of the planet … and could exacerbate the shifting cognitive baseline whereby humans tend to become accustomed to new and often degraded ecosystems and thus forget the nature of the past."

Criticism of the concept and proposed alternatives

Criticism of ecosystem health largely targets the failure of proponents to explicitly distinguish the normative dimension from the descriptive dimension, and has included the following:

• Ecosystem health is in the eye of the beholder. It is an economic, political or ethical judgement rather than a scientific measure of environmental quality. Health ratings are shaped by the goals and preferences of environmental stakeholders. "At the core of debates over the utility of ecosystem health is a struggle over which societal preferences will take precedence."
• Health is a metaphor, not a property of an ecosystem. Health is an abstraction. It implies "good", an optimum condition, but in nature ecosystems are ever-changing transitory assemblages with no identifiable optimum.
• Use of human health and well-being as a criterion of ecosystem health introduces an arrogance and a conflict of interest into environmental assessment, as human population growth has caused much environmental damage.
• Ecosystem health masquerades as an operational goal because environmental managers "may be reluctant to define their goals clearly."
• It is a vague concept. "Currently there are many, often contradictory, definitions of ecosystem health," that "are open to so much abuse and misuse that they represent a threat to the environment."
• "There are in general no clear definitions of what proponents of the concept mean by 'ecosystem'."
• The public can be deceived by the term ecosystem health which may camouflage the ramifications of a policy goal and be employed to pejoratively rank policy choices. "The most pervasive misuse of ecosystem health and similar normative notions is insertion of personal values under the guise of 'scientific' impartiality."

Alternatives have been proposed for the term ecosystem health, including more neutral language such as ecosystem status, ecosystem prognosis, and ecosystem sustainability. Another alternative to the use of a health metaphor is to "express exactly and clearly the public policy and the management objective", to employ habitat descriptors and real properties of ecosystems. An example of a policy statement is "The maintenance of viable natural populations of wildlife and ecological functions always takes precedence over any human use of wildlife." An example of a goal is "Maintain viable populations of all native species in situ." An example of a management objective is "Maintain self-sustaining populations of lake whitefish within the range of abundance observed during 1990-99."

Kurt Jax presented an ecosystem assessment format that avoids imposing a preconceived notion of normality, that avoids the muddling of normative and descriptive, and that gives serious attention to ecosystem definition. (1) Societal purposes for the ecosystem are negotiated by stakeholders, (2) a functioning ecosystem is defined with emphasis on phenomena relevant to stakeholder goals, (3) benchmark reference conditions and permissible variation of the system are established, (4) measurement variables are chosen for use as indicators, and (5) the time scale and spatial scale of assessment are decided.

Related terms

Ecological health has been used as a medical term in reference to human allergy and multiple chemical sensitivity and as a public health term for programs to modify health risks (diabetes, obesity, smoking, etc.). Human health itself, when viewed in its broadest sense, is viewed as having ecological foundations. It is also an urban planning term in reference to "green" cities (composting, recycling), and has been used loosely with regard to various environmental issues, and as the condition of human-disturbed environmental sites. Ecosystem integrity implies a condition of an ecosystem exposed to a minimum of human influence. Ecohealth is the relationship of human health to the environment, including the effect of climate change, wars, food production, urbanization, and ecosystem structure and function. Ecosystem management and ecosystem-based management refer to the sustainable management of ecosystems and in some cases may employ the terms ecosystem health or ecosystem integrity as a goal.

Ecosystem-based management

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Ecosystem-based_management

 Ecosystem-based management is an environmental management approach that recognizes the full array of interactions within an ecosystem, including humans, rather than considering single issues, species, or ecosystem services in isolation. It can be applied to studies in the terrestrial and marine environments with challenges being attributed to both. In the marine realm, they are highly challenging to quantify due to highly migratory species as well as rapidly changing environmental and anthropogenic factors that can alter the habitat rather quickly. To be able to manage fisheries efficiently and effectively it has become increasingly more pertinent to understand not only the biological aspects of the species being studied, but also the environmental variables they are experiencing. Population abundance and structure, life history traits, competition with other species, where the stock is in the local food web, tidal fluctuations, salinity patterns and anthropogenic influences are among the variables that must be taken into account to fully understand the implementation of a "ecosystem-based management" approach. Interest in ecosystem-based management in the marine realm has developed more recently, in response to increasing recognition of the declining state of fisheries and ocean ecosystems. However, due to a lack of a clear definition and the diversity involved with the environment, the implementation has been lagging.

Terrestrial ecosystem-based management (often referred to as ecosystem management) came into its own during the conflicts over endangered species protection (particularly the northern spotted owl), land conservation, and water, grazing and timber rights in the western United States in the 1980s and 1990s.

History

The systemic origins of ecosystem-based management are rooted in the ecosystem management policy applied to the Great Lakes of North America in the late 1970s. The legislation created, the "Great Lakes Basin and the Great Lakes Water Quality Agreement of 1978", was based on the claim that "no park is an island", with the purpose to show how strict protection of the area is not the best method for preservation. This type of management system was however an idea that began long before and evolved through the testing and challenging of common ecosystem management practices.

Before its complete synthesis, the management system's historical development can be traced back to the 1930s. During this time, the scientific communities who studied ecology realized that current approaches to the management of national parks did not provide effective protection of the species within. In 1932, The Ecological Society of America's Committee for the Study of Plant and Animal Communities recognized that US national parks needed to protect all the ecosystems contained within the park in order to create an inclusive and fully functioning sanctuary, and be prepared to handle natural fluctuations in its ecology. Also the committee explained the importance for interagency cooperation and improved public education, as well as challenged the idea that proper park management would "improve" nature. These ideas became the foundation of modern ecosystem-based management. 

As the understanding of how to manage ecosystems shifted, new tenets of the management system were produced. Biologists George Wright and Ben Thompson accounted for the size and boundary limitations of parks and contributed to the re-structuring of how park lines were drawn. They explained how large mammals for example could not be supported within the restricted zones of a national park and in order to protect these animals and their ecosystems a new approach would be needed. Other scientists followed suit, but none were successful in establishing a well-defined ecosystem-based management approach.

In 1979, the importance of ecosystem-based management resurfaced in ecology from two biologists: John and Frank Craighead. The Craigheads found that grizzly bears of Yellowstone National Park could not sustain a population if only allowed to live within park boundaries. This reinforced the idea that a broader definition of what defines an ecosystem needed to be created, suggesting that it be based on the biotic requirements of the largest mammal present.

The idea of ecosystem-based management began to catch on and projects throughout American National Parks reflected the idea of protecting an ecosystem in its entirety and not based on legal or ecological restrictions as previously used. Jim Agee and Darryll Johnson published a book-length report on managing ecosystems in 1988 explaining the theoretical framework management. While they did not fully embrace ecosystem-based management by still calling for "ecologically defined boundaries", they stated the importance of "clearly stated management goals, interagency cooperation, monitoring of management results, and leadership at the national policy levels". Most importantly they demanded the recognition of human influence. It was argued that scientists must keep in mind the "complex social context of their work" and always be moving towards "socially desirable conditions". This need to understand the social aspects of scientific management is the fundamental step from ecological management to ecosystem-based management.

Although it continues to become recognized, a debate over ecosystem-based management continues. Grumbine (1994) believes, while the approach has evolved, it has not been fully incorporated into management practices because the most effective forms of it have yet to be seen. He articulates that the current ecological climate calls for the most holistic approach of ecological management. This is in part due to the rapid decline in biodiversity and because of the constant state of flux in societal and political views of nature. Conflicts over public interest and understanding of the natural world have created social and political climates that require interagency cooperation, which stands as a backbone for ecosystem-based management.

Implementation

Because ecosystem-based management is applied to large, diverse areas encompassing an array of interactions between species, ecosystem components, and humans, it is often perceived as a complex process that is difficult to implement. Slocombe (1998b) also noted that in addition, uncertainty is common and predictions are difficult. However, in light of significant ecosystem degradation, there is a need for a holistic approach that combines environmental knowledge and co-ordination with governing agencies to initiate, sustain and enforce habitat and species protection, and include public education and involvement. As a result, ecosystem-based management will likely be increasingly used in the future as a form of environmental management. Some suggestions for implementing ecosystem-based management and what the process may involve are as follows:

Goals and objectives

Defining clear and concise goals for ecosystem-based management is one of the most important steps in effective ecosystem-based management implementation. Goals must move beyond science-based or science-defined objectives to include social, cultural, economic and environmental importance. Of equal importance is to make sure that the community and stake-holders are involved throughout the entire process. Slocombe (1998a) also stated that a single, end-all goal cannot be the solution, but instead a combination of goals and their relationships with each other should be the focus.

As discussed by Slocombe (1998a), goals should be broadly applicable, measurable and readily observable, and ideally be collectively supported in order to be achievable. The idea is to provide direction for both thinking and action and should try to minimize managing ecosystems in a static state. Goals should also be flexible enough to incorporate a measure of uncertainty and be able to evolve as conditions and knowledge change. This may involve focusing on specific threatening processes, such as habitat loss or introduced invasive species, occurring within an ecosystem. Overall the goals should be integrative, to include the structure, organization and processes of the management of an area. Correct ecosystem-based management should be based in goals that are both "substantive", to explain the aims and importance of protecting an area, and "procedural", to explain how substantive goals will be met.

As described by Tallis et al. (2010), some steps of ecosystem-based management may include:

Scoping

This step involves the acquisition of data and knowledge from various sources in order to provide a thorough understanding of critical ecosystem components. Sources may include literature, informal sources such as aboriginal residents, resource users, and/or environmental experts. Data may also be gained through statistical analyses, simulation models, or conceptual models.

Defining indicators

Ecological indicators are useful for tracking or monitoring an ecosystem's status and can provide feedback on management progress as stressed by Slocombe (1998a). Examples may include the population size of a species or the levels of toxin present in a body of water. Social indicators may also be used such as the number or types of jobs within the environmental sector or the livelihood of specific social groups such as indigenous peoples.

Setting thresholds

Tallis et al. (2010) suggest setting thresholds for each indicator and setting targets that would represent a desired level of health for the ecosystem. Examples may include species composition within an ecosystem or the state of habitat conditions based on local observations or stakeholder interviews. Thresholds can be used to help guide management, particularly for a species by looking at the conservation status criteria established by either state or federal agencies and using models such as the minimum viable population size.

Risk analysis

A range of threats and disturbances, both natural and human, often can affect indicators. Risk is defined as the sensitivity of an indicator to an ecological disturbance. Several models can be used to assess risk such as population viability analysis.

Monitoring

Evaluating the effectiveness of the implemented management strategies is very important in determining how management actions are affecting the ecosystem indicators. Evaluation: This final step involves monitoring and assessing data to see how well the management strategies chosen are performing relative to the initial objectives stated. The use of simulation models or multi-stakeholder groups can help to assess management. 

It is important to note that many of these steps for implementing ecosystem-based management are limited by the governance in place for a region, the data available for assessing ecosystem status and reflecting on the changes occurring, and the time frame in which to operate.

Challenges

Because ecosystems differ greatly and express varying degrees of vulnerability, it is difficult to apply a functional framework that can be universally applied. These outlined steps or components of ecosystem-based management can, for the most part, be applied to multiple situations and are only suggestions for improving or guiding the challenges involved with managing complex issues. Because of the greater amount of influences, impacts, and interactions to account for, problems, obstacles and criticism often arise within ecosystem-based management. There is also a need for more data, spatially and temporally to help management make sound decisions for the sustainability of the stock being studied.

The first commonly defined challenge is the need for meaningful and appropriate management units. Slocombe (1998b) noted that these units must be broad and contain value for people in and outside of the protected area. For example, Aberley (1993) suggests the use of "bioregions" as management units, which can allow peoples involvement with that region to come through. To define management units as inclusive regions rather that exclusive ecological zones would prevent further limitations created by narrow or restricting political and economic policy created from the units. Slocombe (1998b) suggests that better management units should be flexible and build from existing units and that the biggest challenge is creating truly effect units for managers to compare against.

Another issue is in the creation of administrative bodies. They should operate as the essence of ecosystem-based management, working together towards mutually agreed upon goals. Gaps in administration or research, competing objectives or priorities between management agencies and governments due to overlapping jurisdictions, or obscure goals such as sustainability, ecosystem integrity, or biodiversity can often result in fragmented or weak management. In addition, Tallis (2010) stated that limited knowledge of ecosystem components and function and time constraints that can often limit objectives to only those that can be addressed in the short-term.

The most challenging issue facing ecosystem-based management is that there exists little knowledge about the system and its effectiveness. Slocombe (1998b) stated that with limited resources available on how to implement the system it is hard to find support for its use.

Slocombe (1998a) said that criticism of ecosystem-based management include its reliance on analogy and comparisons, too broadly applied frameworks, its overlap with or duplication of other methods such as ecosystem management, environmental management, or integrated ecosystem assessment, its vagueness in concepts and application, and its tendency to ignore historical, evolutionary or individual factors that may heavily influence ecosystem functioning.

Tallis (2010) stated that ecosystem-based management is seen as a critical planning and management framework for conserving or restoring ecosystems though it is still not widely implemented. An ecosystem approach addresses many relationships across spatial, biological, and organizational scales and is a goal-driven approach to restoring and sustaining ecosystems and functions. In addition, ecosystem-based management involves community influence as well as planning and management from local, regional and national government bodies and management agencies. All must be in collaboration in order to develop a desired future of ecosystem conditions, particularly where ecosystems have undergone radical degradation and change. Slocombe (1998b) said that to move forward, ecosystem-based management should be approached through adaptive management, allowing flexibility and inclusiveness to deal with constant environmental, societal, and political change.

Marine systems

Ecosystem-based management for marine environments moves away from the traditional strategies in which single species and single sectors are managed individually; rather it is an integrated approach which considers all key activities, particularly anthropogenic, that affect marine environments. The management must take into account the life history of the fish being studied, its association with the surrounding environment, its place in the food web, where it prefers to reside in the water column and how it is affected by human pressures. The objective is to ensure sustainable ecosystems, thus protecting the resources and services they provide for future generations.

In recent years there has been increasing recognition of disruption to marine ecosystems resulting from climate change, overfishing, nutrient and chemical pollution from land runoff, coastal development, bycatch, habitat destruction and other anthropogenic sources. There are very clear links between human activities and marine ecosystem functioning; this has become an issue of high importance because there are many services provided by marine ecosystems that are declining as a result of these impacts. These services include the provision of food, fuel, mineral resources, pharmaceuticals, as well as opportunities for recreation, trade, research and education.

Guerry (2005) has identified an urgent need to improve the management of these declining ecosystems, particularly in coastal areas, to ensure a sustainable future. Human communities depend on marine ecosystems for important resources, but without holistic management these ecosystems are likely to collapse. It has been suggested that the degradation of marine ecosystems is largely the result of poor governance and that new approaches to management are required. The Pew Oceans Commission and the United States Commission on Ocean Policy have indicated the importance of moving from current piecemeal management to a more integrated ecosystem-based approach.

Stock Assessment

In marine environments, it can be increasingly difficult to determine what part of the population a certain stock comes from. In the case of the Southern bluefin tuna, it is all one taxonomic stock while in the Pacific Northwest, each river has its own stock of pacific salmon and thus, the clear definition of a particular stock can be quite challenging. With knowledge on the specific species life history, stock assessment can be much easier and therefore, knowledge on the animals breeding patterns, juvenile state and morphological patterns are essential.

Dead salmon in spawning season

Bottom up or top down

Post-dip pose

When trying to analyze the specific species, the manager needs to fully understand where the species is in terms of the food web. In the North Sea, the puffin population crashed and no one was quite sure why. After further analysis, they realized that the decline in seabird numbers was due to the sandeel population being severely depleted due to fishing pressures and this is an example of top down. In Alaska, the sea otter was hunted mainly for its pelt and was nearly pushed to extinction. As their numbers dwindled, the kelp beds were disappearing as well at an alarming rate due to the sea urchins having no predators and eating all of the kelp. As the sea otters were removed, the rest of the ecosystem in the food chain beneath them were affected, an example of top-down.

Bycatch

In the Gulf of Mexico, the red snapper is one of the most important economical species there is. However, it is a very difficult species to manage due to the bycatch associated with the shrimping industry. The juveniles are caught in the smaller mesh size used for the shrimp and thus, a large portion of the red snapper population is subject due to mortality not associated with the red snapper fishery.

Key elements

Connections

At its core, ecosystem-based management is about acknowledging interdependency connections, including the linkages between marine ecosystems and human societies, economies and institutional systems, as well as those among various species within an ecosystem and among ocean places that are linked by the movement of species, materials, and ocean currents. Of particular importance is how these factors all react and involve each other. In the Caribbean, the spiny lobster is managed based on a classic population model that for most fishery species works quite well. However, this species will grow and then halt its growth when it need to molt its shell and thus instead of a continuous growth cycle, it will pause its growth and invest its energy in a new shell. To further complicate matters, it slows this process down as it gets older to invest more energy into reproduction thus further deviating itself from the von Bertalanffy model of growth that was applied to it. The more information we can gather about an ecosystem and all of the interconnected factors which affect it, the more capable we will be of better managing that system.

Cumulative impacts

Ecosystem-based management focuses on how individual actions affect the ecosystem services that flow from coupled socio-ecological systems in an integrated fashion, rather than considering these impacts in a piecemeal manner. Loss of biodiversity in marine ecosystems is an example of how cumulative effects from different sectors can impact on an ecosystem in a compounding way. Overfishing, coastal development, filling and dredging, mining and other human activities all contribute to the loss of biodiversity and therefore degradation of the ecosystem. Work is needed prior to the carrying out of the research to understand the total effects that each species can have on each other and also on the environment. It must be carried out every year as well as species are changing their life history traits and their relationship with the environment as humans are continually modifying the environment.

Interactions between sectors

The only way to deal with the cumulative effects of human influences on marine ecosystems is for various contributing sectors to set common goals for the protection or management of ecosystems. While some policies may only affect a single sector, others may affect multiple sectors. A policy for the protection of endangered marine species, for example, could affect recreational and commercial fisheries, mining, shipping and tourism sectors to name a few. More effective ecosystem management would result from the collective adoption of policies by all sectors, rather than each sector creating their own isolated policies. For example, in the Gulf of Mexico there are oil rigs, recreational fisheries, commercial fisheries and multiple tourist attractions. One of the main fisheries is that of the Red Snapper which inhabits much of the Gulf and employs thousands of people in the commercial and recreational fishery. During the Deepwater oil spill it became abundantly obvious that it negatively affected the population numbers as well as the integrity of the catch that was being made. The species not only suffered higher mortality rates but the market was less trusting of the product. An environmental disaster interacted with the commercial, recreational, and economic sector for a specific species.

Changing public perceptions

Not all members of the public will be properly informed, or be fully aware, of current threats to marine ecosystems and it is therefore important to change public perceptions by informing people about these issues. It is important to consider the interest of the public when making decisions about ocean management and not just those who have a material interest because community support is needed by management agencies in order to make decisions. The Great Barrier Reef Marine Park Authority (GBRMPA) faced the issue of poor public awareness in their proposed management strategy which included no-take fishing zones. Olssen (2008) addressed this problem by starting a 'reef under pressure' information campaign to prove to the public that the Great Barrier Reef is under threat from human disturbances, and in doing so were successful in gaining public support.

Bridging science and policy

To ensure that all key players are on the same page, it is important to have communication between managers, resource users, scientists, government bodies and other stakeholders. Leslie and McLeod (2007) stated that proper engagement between these groups will enable the development of management initiatives that are realistic and enforceable as well as effective for ecosystem management. If certain small-scale players are not involved or informed, it is highly unlikely and equally challenging to get them to cooperate as well as to follow the rules that need to be put in place. It is of the utmost importance to have every stakeholder involved with every step of the process to increase the cohesion of the process.

Embracing change

Coupled social-ecological systems are constantly changing in ways that cannot be fully predicted or controlled. Understanding the resilience of ecosystems, i.e. the extent to which they can maintain structure, function, and identity in the face of disturbance, can enable better prediction of how ecosystems will respond to both natural and anthropogenic perturbations, and to changes in environmental management. With how much modification humans are doing to environments, it is important to understand these changes on a yearly basis as well. Some species are changing their life histories, Flounder, due to the increased pressures that humans are placing on the environment. Thus, when a manager or government does an assessment on the ecosystem for a given year, the relationship that a species has to others can change very quickly and thus negate the model that you use for an ecosystem very quickly if not redefined.

Multiple objectives

Ecosystem-based management focuses on the diverse benefits provided by marine systems, rather than on single ecosystem services. Such benefits or services include vibrant commercial and recreational fisheries, biodiversity conservation, renewable energy from wind or waves and coastal protection. The goal is to provide a sustainable fisheries while incorporating the impacts of other aspects on that resource. When managed correctly, an ecosystem-based model can greatly improve not only the resource being managed, but those associated with it.

Learning and adaptation

Because of the lack of control and predictability of coupled social-ecological systems, an adaptive management approach is recommended. There can be multiple different factors that must be overcome (fisheries, pollution, borders, multiple agencies, etc.) to create a positive outcome. Managers must be able to react and adapt as to limit the variance associated with the outcome.

Other examples

Great Bear Rainforest - Canada

The Land and Resource Management Planning (LRMP) was implemented by the British Columbia Government (Canada) in the mid-1990s in the Great Bear Rainforest in order to establish a multiparty land-use planning system. The aim was to "maintain the ecological integrity of terrestrial, marine and freshwater ecosystems and achieve high levels of human well-being". The steps described in the programme included: protect old-growth forests, maintain forest structure at the stand level, protect threatened and endangered species and ecosystems, protect wetlands and apply adaptive management. MacKinnon (2008) highlighted that the main limitation of this program was the social and economic aspects related to the lack of orientation to improve human well-being.

The Great Lakes - Canada and United States

A Remedial Action Plan (RAP) was created during the Great Lakes Water Quality Agreement that implemented ecosystem-based management. The transition, according to the authors, from "a narrow to a broader approach " was not easy because it required the cooperation of both the Canadian and American governments. This meant different cultural, political and regulatory perspectives were involved with regards to the lakes. Hartig et al. (1998) described eight principles required to make the implementation of ecosystem-based management efficacious: "broad-based stakeholder involvement; commitment of top leaders; agreement on information needs and interpretation; action planning within a strategic framework; human resource development; results and indicators to measure progress; systematic review and feedback; and stakeholder satisfaction".

Scallop aquaculture in Sechura Bay, Peru

Peruvian Bay Scallop is grown in the benthic environment. Intensity of the fishery has caused concern over recent years and there has been a shift to more of an environmental management scheme. They are now using food web models to assess the current situation and to calibrate the stocking levels that are needed. The impacts of the scallops on the ecosystem and on other species are now being taken into account as to limit phytoplankton blooms, overstocking, diseases and overconsumption in a given year. This study is proposed to help guide both fisherman and managers in their goal of providing long term success for the fishery as well as the ecosystem they are utilizing.

Dam removal in the Pacific Northwest

The Elwha dam removal in Washington state is the largest dam removal project in the United States. Not only was it blocking several species of salmon from reaching their natural habitat, it also had millions of tons of sediment built up behind it.