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85 Per Cent of Worlds Oyster Reefs have Vanished

by the Fish Site Editor
22 May 2009, at 1:00am

GLOBE - Shellfish Reefs at Risk analysis shows habitat loss has widespread impacts for ecosystems and economies, identifies solutions for bringing oyster reefs back from the brink.

The Nature Conservancy released the first-ever comprehensive global report on the state of shellfish at the International Marine Conservation Congress in Washington, DC. The report, which finds that 85 percent of oyster reefs have been lost worldwide, concludes that oyster reefs are the most severely impacted marine habitat on the planet.

“We’re seeing an unprecedented and alarming decline in the condition of oyster reefs, a critically important habitat in the world’s bays and estuaries,” said Mike Beck, senior marine scientist at The Nature Conservancy and lead author of the report. “However, realistic and cost-effective solutions within conservation and coastal restoration programs, along with policy and reef management improvements, provide hope for the survival of shellfish.”

The report, written by scientists across five continents, from conservation organizations as well as academic and research institutions, focuses primarily on the distribution and condition of native oyster reefs.

Besides being a culinary favorite and a long-standing staple in seafood restaurants around the globe, oysters provide benefits to humans in less obvious ways. For example, they act as natural water filters and improve water quality, provide food and habitat for fish, crabs and birds, and serve as natural coastal buffers that help to protect shorelines and keep coastal marshes intact, an important factor in protecting communities against storm surges and sea-level rise.

Yet the report’s analysis found that oysters are in trouble:

  • In the majority of individual bays around the world, there has been a greater than 90 percent loss of oyster reef habitat. In some areas, the loss of oyster reef habitat exceeds 99 percent -- globally, 85 percent of oyster reefs have been completely lost.

  • Reefs are functionally extinct in many areas, particularly in North America, Australia and Europe, and no are no longer able to provide any of the ecosystem services that benefit people.

  • Most of the world’s remaining wild capture of oysters comes from only five regions on the east coast of North America, and in most of these regions, oyster reefs are in poor condition or worse.

The driving forces behind the decline of oyster reefs include destructive fishing practices, coastal over-development, and associated effects of upstream activities such as altered river flows, dams, poorly managed agriculture and poor water quality. Many of these threats have been around for decades and even centuries, but today there are two main issues that impede oyster recovery efforts.

According to the report, the first is a widespread lack of awareness that shellfish habitats are in trouble. In nearly all cases, shellfish are managed as fisheries, meaning they are viewed solely as a commodity but are not valued for the intrinsic role they play in keeping marine ecosystems healthy and intact. The second challenge is the common perception that as native shellfish decline, non-native shellfish can act as an ecologically suitable replacement. Unfortunately, previous introductions of non-native oysters and other shellfish into new areas have spread disease and have had other negative impacts on the surrounding environment.

“Shellfish provide multiple ecosystem benefits including improved water quality and important habitat for a wide variety of fish and other aquatic life,” said Patricia Montanio, Director of the National Oceanic and Atmospheric Administration (NOAA) National Marine Fisheries Service Habitat Program. “Since 2001, NOAA has worked with the Conservancy to implement successful restoration of shellfish and other coastal habitats. Now more than ever, it’s important that we make a concerted effort to protect, restore and conserve these valuable coastal assets.”

The report lays out specific recommendations drawn from examples around the world, such as the need to elevate native, wild oyster reefs as a priority for habitat management and conservation, carry out large-scale restoration programs, and make better use of protected area policies for shellfish protection.

“We want to raise awareness that the world’s remnant oyster reefs and populations are important, since they may in fact represent some of the last examples of reef habitat produced by a particular species of oyster,” said Christine Crawford, a scientist with the Tasmanian Aquaculture and Fisheries Institute at the University of Tasmania in Australia and one of the co-authors of the report. “We have an opportunity to conserve such reefs in Australia and elsewhere with the results of this assessment.”

Further Reading

- You can view the full report by clicking here.

the Fish Site Editor