(1) The physical, chemical and biological processes that transform and translocate energy or materials in an ecosystem;
(2) The capacity of natural processes and components to provide goods and services that satisfy human needs, either directly or indirectly.Ecosystem functions are conceived as a subset of ecological processes and ecosystem structures.
Ecosystem functions can be defined by “the ecological processes that control the fluxes of energy, nutrients and organic matter through an environment”.
Ecosystem services are processes occurring within an ecosystem that provide benefits to humanity. Marine ecosystems provide many important functions at a global, national and regional level. The seas provide a unique set of goods and services to society, including moderation of climate, processing of waste and toxicants, protection of the coastline, provision of vital food and medicines and are a source of employment for a significant number of people. Our coasts provide space to live and directly and indirectly create wealth, including millions of jobs in industries such as fishing, aquaculture and tourism. See also the article Ecosystem services.
The two definitions are complementary. Jax (2005) added two other elements, leading to the following suite of meanings of the term 'function' within ecology and the environmental sciences: "function refers, in a descriptive sense, (1) to ecological processes and the causal relations that give rise to them, (2) to the role of organisms within an ecological system, (3) to the overall processes that sustain an ecological system (which together determine its "functioning") and (4) to the services a system provides for humans or other organisms" .
Although a distinction is not always made, ecosystem function should be distinguished from ecosystem functioning. The latter refers to the dynamic interaction of an ecosystem as a functional unit with its environment. See also Ecosystem functioning.
There is broad consensus among scientists that ecosystem function is related to biodiversity. Changes in biodiversity will result in altered ecosystem functions, i.e. higher and more efficient functioning rates come from highly diverse communities. This is presumed to be because diverse communities are more likely to contain a greater range of functional traits and environmental sensitivities. High diversity therefore entails opportunities for more efficient resource use as well as providing stability to ecosystem functions in variable environments and in the face of disturbance. Alternatively, systems with species-poor communities are theoretically likely to be functionally poorer, less resistant (capacity to resist change) and resilient (capacity to recover from change) to disturbance than systems with species-rich communities.
Many ecosystems around the world are currently undergoing profound changes in species composition due to the influence of human activity and climate change. It is generally believed that these changes have, more often than not, reduced diversity. The evidence about the consequences of biodiversity loss for the marine ecosystem function is not unequivocal, see the article Disturbances, biodiversity changes and ecosystem stability.
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