From Anchovies to Sardines and Back: Multidecadal Change in the Pacific Ocean -

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Ecosystems

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What is an Ecosystem?

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.

Photo title: Caribbean coral reef in 1960 - artist's impression

Photo credit: Illusion Arts

Why are Ecosystems Important?

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.

Photo title: Intertidal ecosystem, La Jolla, California

Photo credit: F B Michaelis

Changes in Ecosystems

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. See More...

Photo title: Kelp forest past and present

Photo credit: Industrial Light and Magic

All (160)

Institutional Contact (11)

Title

From Anchovies to Sardines and Back: Multidecadal Change in the Pacific Ocean ( DOCUMENT )

Author(s) / Editor(s)

Chavez, F P;

Ryan, J;

Lluch-Cota, S E;

Miguel Niquen, C

Description

In the Pacific Ocean, air and ocean temperatures, atmospheric carbon dioxide, landings of anchovies and sardines, and the productivity of coastal and open ocean ecosystems have varied over periods of about 50 years. In the mid-1970s, the pacific changed from a cool "anchovy regime" to a warm "sardine regime". A shift back to an anchovy regime occurred in the middle to late 1990s. these large-scale, naturally occurring variations must be taken into account when considering human-induced climate change and the management of ocean living resources.

Keywords

FISHERIES;

CLIMATE CHANGE;

ECOSYSTEMS

Geography Keywords

PACIFIC OCEAN

Content Language(s)

English

Web Address

http://www.sciencemag.org

Type of Document

Journal: Journal article