Ecosystems

An ecosystem is a functional unit comprising all the organisms in a particular place interacting with one another and with their environment, and interconnected by an ongoing flow of energy and a cycling of materials. There are many different ways of delimiting an ecosystem. Ecosystems may be defined by size: the whole earth may be regarded as one giant ecosystem. On a smaller scale, dividing the coasts and oceans into 64 Large Marine Ecosystems (LMEs), 200 000 square km or greater and associated with 95 per cent of the fish and shellfish yield of the world, has been useful in the global effort for better management of the coastal zone. On an even smaller scale, vegetation units such as a mangrove forest ecosystem would be in the range of 10 square m to 100 square km. Ecosystems are often defined according to the main primary producer such as kelp, mangrove or coral reef. The boundaries of these systems are taken as the boundaries of the vegetation type. Ecosystems may also be defined by geographical boundaries such as wet coastal, intertidal and littoral, estuaries and enclosed seas, coral reefs, continental shelves and deep ocean.

Ecosystem function includes those ecosystem level processes that contribute to the well being of mankind. Beneficial ecosystem functions are called ecosystem services and the oceans account for about two-thirds of the value of ecosystem services on a global basis. Ecosystems are important for coastal and ocean management. We need to encompass entire ecosystems as units as the trend for management of living resources moves from single species to multispecies assemblages. Measures designed to optimize the natural productivity of groups of target species should include consideration of related populations and their environment. This will provide a balance between maintaining productivity of the ecosystem and optimizing the yield of commercial species.

One commonly asked question is whether continued species losses or changes in abundance are likely to seriously harm ecosystem function. Marine biodiversity remains one important aspect of ecosystem services. Other concerns about ecosystem function relate to the loss of stability of the ecosystem, even though it may be able to exist at alternative stable states; widespread structural change by humans, often made less noticeable by shifting baselines; and habitat destruction. Ecosystems require plans for management on a sustainable basis and for research into areas where there is insufficient information, at the same time as monitoring their health over the long term. For additional information about changes in the environment and the productivity of marine ecosystems and marine resources, go to See More.