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Coral Reef Destruction Worst in 3000 years

Scientists agree the problem is severe

Many scientists now agree that coral reefs are being damaged by global climate change. The first warning signs came from bleaching, which occurs when warmer waters force corals to expel their symbiotic algae. During the 1997- 98 El Nino, reefs bleached throughout the world, and there were mass deaths of coral in the Caribbean.

A report on the status of coral reefs by the Global Coral Reef Monitoring Network found that one-fourth of the world's reefs had been eliminated and another third were severely threatened. Cores drilled from Caribbean reefs off Belize show that nothing like this has happened for at least 3000 years.

"This is the first palaeontological evidence that directly links the new bleaching related mass mortality to global warming," says Rich Aronson from the Dauphin Island Sea Lab in Alabama, who did the research. "It's clearly a cause for grave concern."

High water temperatures also make coral reefs more susceptible to marine diseases. Elevated concentrations of carbon dioxide, the main cause of global warming, also directly harm corals, whose skeletal growth declines in carbon dioxide enriched water.

Aronson stated that "there is clearly cause for grave concern for the future of coral reefs if present climate trends continue." Aronson's work is supported by evidence from cores drilled at 16 reefs throughout the tropics, which have been analysed by Mark Eakin and his colleagues at the World Data Center for Paleoclimatology in Boulder, Colorado.

"There is a definite increase in temperatures in the last 400 years, with warmer, wetter conditions", says Eakin. "This must be a result of human activity. The rate is extreme and we cannot explain it any other way."

If current trends continue, corals may become too fragile to support reef structures as we know them, says Joan Kleypas of the National Center for Atmospheric Research. "There is no evidence to suggest corals are acclimatising to the changes", she says.

See also story on global warming and salmon