An ecological concept which helps to explain the relationships and interactions between one or more living organisms and their physical, biological, and chemical environment (eg a pond and its associated plants, fish, insects, birds, and mammals). The concept is helpful in describing interactions at any level, from the individual plant in its community to planet Earth. The study of ecosystems is commonly based on transfers of energy along a food chain by examining four elements: abiotic or inorganic and dead organic substances (eg inorganic compounds in soil and water); green plants or producers, which fix energy from the Sun by photosynthesis and use inorganic material from the soil or atmosphere to manufacture complex organic substances; consumers (eg birds, insects, mammals) which use the energy fixed by plants; and decomposers (eg bacteria, fungi), which break down dead organisms, releasing nutrients back to the environment for use by the producers. In most natural ecosystems, several food chains interact to form complex food or energy webs. An ecosystem is a convenient model which does not, however, convey the complexity of the interactions which actually take place.
An ecosystem, a contraction of "ecological" and "system", refers to the collection of components and processes that comprise, and govern the behavior of, some defined subset of the biosphere. To many people, ecosystems (like any other type of system), are governed by the rules of systems science and cybernetics, as applied specifically to collections of organisms and relevant abiotic components. To others, ecosystems are primarily governed by stochastic events, the reactions they provoke on non-living materials and the corresponding responses by organisms.
Overview
In general terms an ecological system can be thought of as an assemblage of organisms (plant, animal and other living organisms—also referred to as a biotic community or biocoenosis) living together with their environment (or biotope), functioning as a loose unit.
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. 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". Early conceptions of an ecosystem were as a structured functional unit in equilibrium of energy and matter flows among constituent elements. Some considered this vision limited,and preferred to define an ecosystem in terms of cybernetics. Introduction of new elements, whether abiotic or biotic, into an ecosystem tend to have a disruptive effect. Under this deterministic vision, the abstract notion of ecological health attempts to measure the robustness and recovery capacity for an ecosystem; Reddingius, 1996), view an ecosystem as an expression of stochastic events, and corresponding responses from organisms. Thus, ecosystems result from the sums of infinite individual responses of organisms to stimuli from non-living and living elements in the environment. As the number of species in an ecosystem is higher, the number of stimuli is also higher. In this vision, ecosystems are not regulated and there is no balance of nature. Hence, stochastists see territorial behaviour as a regulatory mechanism at the species level but not at the ecosystem level.
History
The term ecosystem first appeared in a 1935 publication by the British ecologist Arthur Tansley (1935). Tansley expanded on the term in his later work, adding the ecotope concept to define the spatial context of ecosystems (Tansley, 1939). It was subsequently applied by H.T.Odum, sometimes called the 'father' of ecosystems ecology, in founding the transdiscipline known as systems ecology.
Hotspots
Ecosystem "hotspots" are ecosystems and the species they support that are considered at risk or endangered.
Canada
Atlantic coastal plain flora: Atlantic Coastal Plain Flora (ACPF) Carolinian forest Tall grass prairie South Okanagan’s antelope-brush ecosystem Coastal Douglas fir forest Eelgrass meadow(Source: Canadian Geographic Online)
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