July 26, 2001. Copyright 2001. Graphic News. All rights reserved.

Ancestors triggered collapse of marine ecosystems by overfishing

LONDON, July 26, Graphic News: Dying coral reefs, dwindling shellfish populations, shrinking seagrass beds and other collapses of the worldÕs coastal ecosystems are often blamed on pollution or global warming.

Now a group of 16 scientists and academicians from around the world argue that these trends were set into motion by a much older human transgression: overfishing. 

Beginning long before Columbus and accelerating rapidly in colonial and modern times, people have radically overfished marine mammals, large fishes and shellfish, according to the paper in the journal Science.

ÒSuccessful management and restoration of coastal marine ecosystems has failed in part because of a lack of understanding the deeper historical causes of collapses in these ecosystems,Ó said Dr. Jim Estes, a research ecologist with the Western Ecological Research Center in Santa Cruz, Calif., one of the authors of the article. 

The scientists examined paleoecological records from about 125,000 years ago, historic, and modern ecological data to track ecological changes in kelp forests, coral reefs, seagrass beds, estuaries, and offshore deep-water communities. 

The scientists note that overfishing precedes pollution, physical destruction of habitats, disease, and human-induced climate change. They found that unrelenting exploitation accelerated and intensified as population growth, technological advances and eventual expansion to a global market occurred. 

The first major human disturbance to all of the ecosystems they examined was always overfishing of the large vertebrates and shellfish. Much later other events followed: pollution, overenrichment of waters from nutrients, disease outbreaks, habitat destruction, invasion of introduced species and human-caused climate change.

While a few species like the StellarÕs sea cow of the North Pacific and the sea mink of the Gulf of Maine were fished to extinction, many others became ecologically Òextinct,Ó like the sea otter, which did not make a comeback from intense exploitation until afforded protection in the 20th century. 

The scientists also found that signs of overfishing could be masked for long periods of time when multiple species occupied similar niches in an ecosystemÕs structure and could fill a similar function of an overfished species. 

ÒSince most ecological studies of coastal marine ecosystems have been conducted since the 1950s, scientists have had first-hand knowledge of only the recent structure and function of these ecosystems,Ó said Estes. ÒWe fear that even more marine ecosystems may soon be at risk of collapse.Ó
/ENDS
Sources: Science, United States Geological Survey