Climate change has contributed to a flattening of the complex, multi-layered architecture of Caribbean coral reefs, compromising their role as a nursery for fish stocks and a buffer against tropical storms, a study shows.

The analysis of 500 surveys of 200 reefs, conducted between 1969 and 2008, showed the most complex types of reef have been virtually wiped out across the entire Caribbean.

Such reefs - typified by Table Corals of over 1 meter across and huge antler-shaped Staghorn Corals - act as a sanctuary for local fish and a hunting ground for larger, commercially fished species.

Many have been replaced with the flattest types of rubble-strewn reef, which now cover about three quarters of the Caribbean's reef area, up from about a fifth in the 1970s, said the study, published in the Royal Society journal Biology Letters.

The biggest impact has occurred in the last decade, said the report by researchers from Britain's University of East Anglia and Canada's Simon Fraser University.

"Lack of ... refuges for species with commercial importance, such as lobsters and large fishes, may compromise the long-term sustainability of fisheries and fishing communities," the report said.

Flatter reefs are also less effective in protecting coastal homes and villages from storm swells and tidal surges.

Hurricanes

"The importance of this is going to increase," said Lorenzo Alvarez of the University of East Anglia, who led the study.

"Many scientists think there will be more hurricanes in the future."

The degradation of Caribbean reefs is not entirely linked to climate change, with disease killing about 90 percent of Elkhorn and Staghorn Corals in the 1970s, but a second period of coral destruction is now under way.

New damage is typified by "coral bleaching," which occurs when the tiny organisms that build coral reefs become stressed and abandon their colonies.

"We suggest that the last period of decline is partly due to climate change, but also due to several other human impacts such as over-fishing and coastal development," Alvarez said. "In future, we'll need to change our behavior and reduce the stress on the reefs."

(Shanghai Daily via Agencies June 11, 2009)