HONG KONG — Blasted by dynamite, contaminated with poisons, and smothered by pollution, coral reefs are dying faster than previously thought, according to a study published yesterday by the United Nations.
The UN Environment Program's World Conservation Monitoring Center said it found that reefs worldwide occupy a much smaller area than previously thought, and that virtually all of Southeast Asia's reefs are threatened.
The world's reefs cover 113,720 square miles, about half the size of France and less than one-tenth of a percent of the oceans. They are spread among 101 countries and territories.
The survey "clearly shows that coral reefs are under assault," said Klaus Toepfer, the UN Environment Program's executive director. "They are rapidly being degraded by human activities."
In Asia, home to the greatest diversity of coral species, the widespread practice by fishermen of using dynamite or cyanide to stun and catch fish that live in reefs has caused great damage, the study found. Pollution is another hazard.
Sewage and fertilizer runoff breed algae that crowd out and smother coral. Global warming is also believed to have damaged reefs in recent years by causing bleaching.
The algae, which live on the coral's calcium skeleton and generate its spectacular pink, green and blue hues, provide the reef with nutrients. Coral can live for short periods without algae, but reefs die if the coat is lost permanently.
"Each of these pressures is bad enough in itself, but together, the cocktail is proving lethal," Toepfer said in a statement.
Coral reefs provide vital marine ecosystems for fisheries and wildlife. They help prevent coastal erosion and draw tourists. Some species of coral provide a source of chemical compounds for medicines, including AZT, a treatment for people infected with HIV.
The study found that risks to coral were severe in the three countries with the largest reefs: Indonesia, Australia, and the Philippines.
Indonesia has 20,400 square miles of reefs, Australia has 19,584 square miles and the Philippines has 10,000 square miles.
In Thailand and the Philippines, about 97 percent of the reefs are threatened; in Indonesia, 82 percent; in Malaysia, 91 percent; Papua New Guinea, 46 percent and Australia, 32 percent, according to the study.
The UN Environment Program's survey is one of the most detailed assessments of coral reefs and the first to document the size of reef areas in each country worldwide.
Previous estimates of reef size were based on simpler maps and models and were up to 10 times larger than the new map, said Mark Spalding, lead author of the study. Reefs are deteriorating in almost every country, and marine conservation is failing to protect them, even in areas designated as protection zones, Spalding said.
"One of the saddest facts about the demise of reefs is that it is utterly nonsensical," said Spalding. "Protecting and managing reefs is not just for the good of the fishes. In every case, it also leads to economic and social benefits for local communities."