May 22, 2009

Habitat Loss Pushing World’s Reefs To “˜Functional Extinction’

A new study of the world's shrinking marine habitats suggests that a large decline in shellfish populations could be having a disastrous effect on already vulnerable ecosystems.

In the study, published by The Nature Conservancy, researchers warned that some 85 percent of the planet's oyster reefs have already disappeared and that many of those remaining are now "functionally extinct."

The report, which experts in the field have called the first global assessment of its kind, claims that environmentally unsustainable fishing practices and coastal developments are responsible for the dramatic declines.

Mike Beck, adjunct Professor with the Global Marine Initiative at The Nature Conservancy and lead author of the report, said that the group's research showed that oyster reefs have been the habitats most devastated by modern fishing and development practices.

"We're seeing unprecedented and alarming decline in the condition of oyster reefs, a critically important habitat in the world's bays and estuaries," Beck explained.

Conducted by scientists spread out across five continents, the report claims that coral reefs in a number of regions such as North America, Australia and North America are on the brink of extinction.

"Centuries of intensive fisheries extraction exacerbated by more recent coastal degradation have put oyster reefs near or past the point of functional extinction worldwide," read the study.

"However, realistic and cost effective solutions within conservation and coastal restoration programs, along with policy and reef management programs provide hope for the survival of shellfish," Professor Beck added optimistically.

Oysters perform a number of vital functions within their ecosystems, such as filtering water, recycling nutrients in detritus and serving as a food source for a variety of other organisms.

The group's careful examination of these ecosystems honed in on several "driving forces" responsible for the swift decline of coral reefs in recent years.  Among them were "destructive fishing practices, coastal overdevelopment, poorly managed agriculture and poor water quality."

Although scientists and environmentalists alike have been warning about these problems since at least the 1970's, Beck's team identified two main barriers hindering recovery efforts.

The first problem has been a lack of awareness that shellfish habitats are in grave danger, and the second has been the assumption that other non-native varieties of shellfish can be introduced to take the place of declining native species.

"We want to raise awareness that the world's remnant oyster reefs and populations are important, since they represent some of the last examples of reef habitats produced by a particular species of oyster," explained Dr. Christine Crawford of the University of Tasmania, a co-author of the study.

"We have an opportunity to conserve such reefs in Australia and elsewhere with the results of this assessment," she added.

Some of the report's recommendations included adding native, wild oysters to the list of animals needing official endangered species status, while also extending and rigidly enforcing existing policies designed to protect the fragile reefs.

Mary Seddon, chair of the International Union for Conservation of Nature's Species Survival Commission Mollusk Specialist Group, believes that creating a tight network of protected marine areas while at the same time improving water quality by restricting the amount of sediment flowing into estuaries are critical steps in attempting to rescue several oyster species from extinction.

"By putting protected areas in place and maintaining them, you are reducing the impact of further habitat degradation," Seddon said. "You can't have exploitation."


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