• Croatian: ekosustav, ekosistem
• Czech: ekosystém
• Dutch: ecosysteem
• Estonian: ökosüsteem
• Finnish: ekosysteemi
• French: écosystème
• Greek: οικοσύστημα (oikosýstima)
• Icelandic: vistkerfi

An ecosystem is a natural unit consisting of all plants, animals and micro-organisms (biotic factors) in an area functioning together with all of the non-living physical (abiotic) factors of the environment.

Overview

• Chaparral
• Coral reef
• Desert
• Greater Yellowstone Ecosystem
• Human ecosystem
• Large marine ecosystem
• Littoral zone
• Marine ecosystem
• Rainforest
• Savanna
• Subsurface Lithoautotrophic Microbial Ecosystem
• Taiga
• Tundra
• Urban ecosystem

Ecosystem topics

Classification

Ecosystems have become particularly important politically, since the Convention on Biological Diversity (CBD) - ratified by more than 175 countries - defines "the protection of ecosystems, natural habitats and the maintenance of viable populations of species in natural surroundings" as one of the binding commitments of the ratifying countries. This has created the political necessity to spatially identify ecosystems and somehow distinguish among them. The CBD defines an "ecosystem" as a "dynamic complex of plant, animal and micro-organism communities and their non-living environment interacting as a functional unit".

With the need of protecting ecosystems, the political need arose to describe and identify them within a reasonable time and cost-effectively. Vreugdenhil et al. argued that this could be achieved most effectively by using a physiognomic-ecological classification system, as ecosystems are easily recognizable in the field as well as on satellite images. They argued that the structure and seasonality of the associated vegetation, complemented with ecological data (such as elevation, humidity, drainage, salinity of water and characteristics of water bodies), are each determining modifiers that separate partially distinct sets of species. This is true not only for plant species, but also for species of animals, fungi and bacteria. The degree of ecosystem distinction is subject to the physiognomic modifiers that can be identified on an image and/or in the field. Where necessary, specific fauna elements can be added, such as periodic concentrations of animals and the distribution of coral reefs.

Several physiognomic-ecological classification systems are available: Physiognomic-Ecological Classification of Plant Formations of the Earth (a system based on the 1974 work of Mueller-Dombois and Heinz Ellenberg, and developed by UNESCO), and the Land Cover Classification System (LCCS), developed by the Food and Agriculture Organization (FAO). Several aquatic classification systems are available, and an effort is being made by the United States Geological Survey (USGS) and the Inter-American Biodiversity Information Network (IABIN) to design a complete ecosystem classification system that will cover both terrestrial and aquatic ecosystems.

Ecosystem services

Ecosystem services are “fundamental life-support services upon which human civilization depends,”i and can be direct or indirect. Example of direct ecosystem services are: pollination, wood, erosion prevention etc. Indirect services could be considered climate moderation, nutrient cycles, detoxifying natural substances and many more.

Ecosystem legal rights

The borough of Tamaqua, Pennsylvania passed a law giving ecosystems legal rights. The ordinance establishes that the municipal government or any Tamaqua resident can file a lawsuit on behalf of the local ecosystem. Other townships, such as Rush, followed suit and passed their own laws.

This is part of a growing body of legal opinion proposing 'wild law'. Wild law, a term coined by Cormac Cullinan (a lawyer based in South Africa), would cover birds and animals, rivers and deserts.

Function and biodiversity

From an anthropological point of view, many people see ecosystems as production units that of goods and services. Among some of the most common goods produced by ecosystems, is wood by forest ecosystems and grass for cattle by natural grasslands. Meat from wild animals, often referred to as bush meat in Africa, has proven to be extremely successful under well-controlled management schemes in South Africa and Kenya. Much less successful has been the discovery and commercialization of substances of wild organism for pharmaceutical purposes. Services derived from ecosystems are referred to as ecosystem services. They may include (1) facilitating the enjoyment of nature, which may generate many forms of income and employment in the tourism sector, often referred to as eco-tourisms, (2) water retention, thus facilitating a more evenly distributed release of water, (3) soil protection, open-air laboratory for scientific research, etc.

A greater degree of species diversity or biological diversity - popularly referred to as Biodiversity - of an ecosystem may contribute to greater resilience of an ecosystem, because there are more species present at a location to respond to a factor of change and thus "absorb" or reduce its effects, thus reducing the effect before its structure is fundamentally changed to a different state. This is not universally the case and there is no proven relationship between the species diversity of an ecosystem and its ability to provide goods and services on a sustainable level: Humid tropical forest produce very little goods and direct services and are extremely vulnerable to change, while many temperate forests readily grow back to their previous state of development within a lifetime after felling or a forest fire. Some grasslands have been exploited sustainably for thousands of years (Mongolia, Africa, European peat and mooreland communities).

The study of ecosystems

Ecosystem dynamics

Introduction of new elements, whether biotic or abiotic, into an ecosystem tend to have a disruptive effect. In some cases, this can lead to ecological collapse or "trophic cascading" and the death of many species belonging to the ecosystem in question. Under this deterministic vision, the abstract notion of ecological health attempts to measure the robustness and recovery capacity for an ecosystem; i.e. how far the ecosystem is away from its steady state.

Often, however, ecosystems have the ability to rebound from a disruptive agent. The difference between collapse or a gentle rebound is determined by two factors -- the toxicity of the introduced element and the resiliency of the original ecosystem.

Ecosystems are primarily governed by stochastic (chance) events, the reactions they provoke on non-living materials and the responses by organisms to the conditions surrounding them. Thus, an ecosystem results from the sum of myriad individual responses of organisms to stimuli from non-living and living elements in the environment. The presence or absence of populations merely depends on reproductive and dispersal success, and population levels fluctuate in response to stochastic events. As the number of species in an ecosystem is higher, the number of stimuli is also higher. Since the beginning of life, in this vision, organisms have survived continuous change through natural selection of successful feeding, reproductive and dispersal behavior. Through natural selection the planet's species have continuously adapted to change through variation in their biological composition and distribution. Mathematically it can be demonstrated that greater numbers of different interacting factors tend to dampen fluctuations in each of the individual factors. Given the great diversity among organisms on earth, most of the time, ecosystems only changed very gradually, as some species would disappear while others would move in. Locally, sub-populations continuously go extinct, to be replaced later through dispersal of other sub-populations. Stochastists do recognize that certain intrinsic regulating mechanisms occur in nature. Feedback and response mechanisms at the species level regulate population levels, most notably through territorial behaviour. Andrewatha and Birch (1954) suggest that territorial behaviour tends to keep populations at levels where food supply is not a limiting factor. Hence, stochastists see territorial behaviour as a regulatory mechanism at the species level but not at the ecosystem level. Thus, in their vision, ecosystems are not regulated by feedback and response mechanisms from the (eco)system itself and there is no such thing as a balance of nature.

If ecosystems are indeed governed primarily by stochastic processes, they may be somewhat more resilient to sudden change, as each species would respond individually. In the absence of a balance of nature, the species composition of ecosystems would undergo shifts that would depend on the nature of the change, but entire ecological collapse would probably be less frequently occurring events.

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. See also Relational order theories, as to fundamentals of life organization.

Ecosystem ecology

Ecosystem ecology is the integrated study of biotic and abiotic components of ecosystems and their interactions within an ecosystem framework. This science examines how ecosystems work and relates this to their components such as chemicals, bedrock, soil, plants, and animals. Ecosystem ecology examines physical and biological structure and examines how these ecosystem characteristics interact]]

The relationship between systems ecology and ecosystem ecology is complex. Much of systems ecology can be considered a subset of ecosystem ecology. Ecosystem ecology also utilizes methods that have little to do with the holistic approach of systems ecology. However, systems ecology more actively considers external influences such as economics that usually fall outside the bounds of ecosystem ecology. Whereas ecosystem ecology can be defined as the scientific study of ecosystems, systems ecology is more of a particular approach to the study of ecological systems and phenomena that interact with these systems.

Systems ecology

Systems ecology is an interdisciplinary field of ecology, taking a holistic approach to the study of ecological systems, especially ecosystems. Systems ecology can be seen as an application of general systems theory to ecology. Central to the systems ecology approach is the idea that an ecosystem is a complex system exhibiting emergent properties. Systems ecology focuses on interactions and transactions within and between biological and ecological systems, and is especially concerned with the way the functioning of ecosystems can be influenced by human interventions. It uses and extends concepts from thermodynamics and develops other macroscopic descriptions of complex systems.

The Millennium Ecosystem Assessment

In 2005, the largest ever assessment of the earth's ecosystems was conducted by a research team of over 1,000 scientists. The findings of the assessment were published in the multi volume Millennium Ecosystem Assessment, which concluded that in the past 50 years humans have altered the earth's ecosystems more than any other time in our history.

See also

• Biodiversity Action Plan
• Biogeochemical cycle
• Biome
• Biosphere
• Biosphere 2
• Ecological economics
• Ecological yield
• Ecoregion
• Ecosystem diversity
• Ecosystem ecology
• Ecosystem engineer
• Ecosystem model
• Ecosystem services
• Ecosystem valuation
• Edge effect
• Eugene Odum
• Food chain
• Invasive species
• Landscape ecology
• Leaf

References

Further reading

• Andrewartha, H.G., and L.C. Birch. 1954. The distribution and abundance of animals. Univ. of Chicago Press, Chicago, IL.
• Boer, P.J. den, and J. Reddingius. 1996. Regulation and stabilization paradigms in population ecology. Population and Community Biology Series 16. Chapman and Hall, New York. 397 pg.
• Ecological Society of America, Ecosytem Services, Ecological Society of America. 25 May 2007
• Ehrlich, Paul; Walker, Brian “Rivets and Redundancy”.BioScience.vol.48.no.5. May 1998. pp. 387. American Institute of Biological Sciences.
• Grime, J.P. "Biodiversity and Ecosystem Function: The Debate Deepens." Science Vol. 277. no. 533029 Aug 1997 pp. 1260 - 1261. 25 May 2007
• Groom , Martha J., and Gary K. Meffe. Principles of Conservation Biology. 3. Sunderland, MA: Sinauer Associates, Inc, 2006.
• Lawton, John H., What Do Species Do in Ecosystems?], Oikos, December, 1994. vol.71,no.3.
• Lindeman, R.L. 1942. The trophic-dynamic aspect of ecology. Ecology 23: 399-418.
• Ranganathan, J & Irwin, F. (2007, May 7). Restoring Nature's Capital: An Action Agenda to Sustain Ecosystem Services
• Patten, B.C. 1959. An Introduction to the Cybernetics of the Ecosystem: The Trophic-Dynamic Aspect. Ecology 40, no. 2.: 221-231.
• Tansley, A.G. 1935. The use and abuse of vegetational concepts and terms. Ecology 16: 284-307.
• Tansley, A.G. 1939. The British Islands and their Vegetation. Volume 1 of 2. University Press, Cambridge, Cambridge, United Kingdom. 484 pg.
• Vreugdenhil, D., Terborgh, J., Cleef, A.M., Sinitsyn, M., Boere, G.C., Archaga, V.L., Prins, H.H.T., 2003, Comprehensive Protected Areas System Composition and Monitoring, IUCN, Gland, Switzerland. 106 pg.

External links

• The Ecosystem
• Bering Sea Climate and Ecosystem: current status
• Arctic Climate and Ecosystem: current status
• Millennium Ecosystem Assessment (2005)
• Teaching about Ecosystems
• The State of the Nation's Ecosystems (U.S.)
• Ecosystem Services
• ECOTRON