for National Geographic News
Corals are rapidly disappearing from reefs in the Caribbean and unless conservation actions are taken immediately the trend may prove irreversible, according to British scientists who performed the first ever basin-wide survey of coral reef decline.
"We all knew it was bad, but not this bad," said Isabelle Côté, a biologist at the University of East Anglia in Norwich, England.
Côté and colleague Toby Gardner together with Jennifer Gill, Alastair Grant, and Andrew Watkinson from the Tyndall Centre for Climate Change Research compiled and analyzed data from 263 separate sites across the Caribbean and found that hard coral cover on the reefs has dropped from approximately 50 percent to 10 percent over the last three decades.
Researchers have generally assumed that the rate of coral decline on Caribbean reefs was dramatic, but prior to this study the magnitude and geographic extent of the problem was unknown, say the researchers. Previous studies were small-scale and site-specific.
John McManus, director of the National Center for Caribbean Coral Reef Research at the University of Miami in Florida, said that the results of this study are consistent with the extrapolations he and others have made in recent years, but he nevertheless finds this study's results and those of others depressing.
"I set up and ran ReefBase for a whilethe global database on coral reefs. I felt like I was something like an editor of obituaries," he said.
The study by Côté, Gardner, and colleagues was posted to the Science Express website on July 17. It will also be published in an upcoming issue of the journal Science.
Cause of Decline
The researchers report that there is "no convincing evidence" that the rate of coral decline on Caribbean reefs can be attributed to global warming, but that it is rather the result of several local natural and human factors.
"Coral bleachingrelated mainly to rising sea temperaturehas affected other parts of the world to a much greater extent than the Caribbean so far," said Côté. "However, the threat of climate change remains a serious concern for the future."
The major factors for coral decline in the Caribbean include overfishing, which removes fish species that eat algae. Without predators, the algae grow more quickly than the corals and smother them, especially young corals looking to get a foothold on the reef.
Other causes of the decline are sedimentation from deforestation and land development, pollution, disease, and storms such as Hurricane Allen in 1980 which combined with a few other stressors nearly wiped out corals in Jamaica.
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