Life in the Balance: Coral Reefs Are Declining

July 7, 2008— -- Coral reefs — a key element in ocean ecosystems that provide not only coastline protection but billions of dollars in benefits from tourism, as well as ingredients used in cutting-edge medicines — are increasingly threatened from the effects of global warming and other hazards, according to a new U.S. government report.

The report estimates that nearly half of the coral reefs in areas from the Caribbean to the Pacific "are not in good condition and are continuing steadily on a long-term decline."

"It's a pretty alarming situation," said Jeannette Waddell, the report's co-editor and a marine biologist with the National Oceanic and Atmospheric Administration's National Ocean Service.

"Coral reefs around the world are confronted by the same types of threats. In some places it is worse. In some places, it's slightly better. But we're finding that even remote reefs are showing signs of decline," she told ABC News.

The NOAA report looked at the health of coral reefs in 15 areas under the jurisdiction of the United States and a group of countries called the Pacific Freely Associated States, which include Palau, the Marshall Islands and Micronesia.

A major threat facing corals is climate change, the report says, which affects coral reefs in multiple ways.

First, warmer ocean temperatures cause corals to expel the colorful living algae in their tissues, leaving them with a "bleached" white look.

"It really stresses out the coral and makes them more susceptible to things like disease," Waddell said.

A major bleaching and disease event in 2005 devastated coral reefs across the Caribbean. In the U.S. Virgin Islands and Puerto Rico, scientists say an average of 50 percent of the coral was lost. Some areas lost 90 percent of their coral.

Another problem for corals is that human-induced climate change is altering the chemistry of the oceans, making them more acidic. It happens as fossil fuels are burned, releasing carbon dioxide into the atmosphere. Much of that carbon dioxide is absorbed by the ocean, which becomes more corrosive.