for National Geographic News
Coral reefs in the Indian and Pacific Oceans are dying off much quicker than previously thought, a new study shows.
For the last two decades, Indo-Pacific reefs have shrunk by 1 percent each year—a loss equivalent to nearly 600 square miles (1,553 square kilometers). That makes the rate of reef loss about twice the rate of tropical rain forest loss.
The research also revealed that the decline began in the late 1960s—much earlier than had been assumed.
"Twenty or 30 years ago reefs with a high cover of coral were fairly common," said study co-author Elizabeth Selig, a marine ecologist from the University of North Carolina.
"Today there are comparatively few reefs in the Indo-Pacific that we would traditionally think of as being pristine."
The study is the first to conduct a regional, long-term assessment of coral reef health in the Indo-Pacific region, which is home to 75 percent of the world's coral reefs and the greatest diversity of coral and fish. (See coral reef photos.)
Researchers compiled more than 6,000 underwater surveys, which were conducted between 1968 and 2004, in ten subregions of the Indo-Pacific. These included Indonesia, the Philippines, and Australia's Great Barrier Reef. (See a map of the region.)
Each survey measured the percentage of seafloor covered of hard corals—a key indicator of reef health.
"Hard corals are the foundation species of coral reefs," said study co-author John Bruno, a marine ecologist at the University of North Carolina.
"It is like measuring the amount of canopy a rain forest has." (Get rain forest facts, photos, and video.)
A Consistent Pattern
Bruno and Selig found that hard-coral cover on Indo-Pacific reefs currently averages 22 percent—a much lower figure than expected. The percentage is also surprisingly consistent across the region.
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