Coral reefs face the threat of extinction.

• Author: Weber, Peter

As a result of global warming, ozone depletion, and pollution, these fragile marine growths are among the most endangered ecosystems on Earth.

IN SEPTEMBER, 1987, fishermen along the southwest coast of Puerto Rico reported that the reef's normally beige corals had turned bright white. At first, marine scientists Lucy Bunkley-Williams and Ernest Williams, Jr., assumed it was an ordinary case of bleaching. Corals bleach if stunned by a number of stresses, including extremely low tide, freshwater flood, pollution, and abnormally low or high water temperatures. Although they can die if the strain is not relieved, in the experience of both fishermen and scientists, bleaching normally was nothing to worry about.

When the two scientists took a dive to examine the reef, they found that its corals had bleached to greater depths than they ever had seen. They became more concerned as accounts of bleaching arrived from Puerto Rico's southern coast and the entire Caribbean. Soon, reports from throughout the tropics revealed the most widespread case of coral bleaching in history. Reefs in every major region of the world were touched.

Because many of the reports mentioned higher than usual water temperatures, some people thought that scientists had found the proverbial canary in the coal mine that would prove that global warming was under way, but this was not the case. Mass bleaching adds to the growing body of evidence--and may be a harbinger of what is to come--but only a long-term trend in global temperatures can confirm definitively that climate change has begun.

Although inconclusive, the debate over mass bleaching and global warming at least drew some needed attention to another global environmental trend--the decline of coral reefs. They already are suffering from a broad array of stresses, including coastal pollution from deforestation and crowded coastlines, which is choking them, and overexploitation by coral miners, fishermen, and tourists, who are destroying and depleting them. A study from the World Conservation Union and the United Nations Environment Programme (UNEP) in the 1980s found that people had damaged or destroyed significant amounts of reef off 93 countries. Reefs, it turns out, are among the most endangered ecosystems on Earth.

They are underwater marvels of fluorescent colors, fantastic shapes, and improbable creatures such as delicate purple sea fans, blood-red sponges, blue-spotted groupers, spiny pufferfish, snorkel-nosed moray, poisonous scorpionfish, giant clams and manta rays, and yellow-lip snakes. Their biological riches, though, hold value far beyond their beauty. After tropical rain forests, coral reefs may be the most biologically diverse ecosystem, holding a substantial portion of the underpinnings of life on the planet. They form what is thought to be the most species-rich ecosystem in the oceans, the crucible of life some 3,000,000,000 years ago. Covering just 0.17% of the ocean floor, an area the size of Texas, coral reefs are home to perhaps one-quarter of all marine species, earning them the title "the tropical rain forests of the oceans." Only the little-explored deep ocean floor could rival the marine biological diversity of coral reefs.

Like the rain forests, reefs hold considerable untapped potential to contribute to science, particularly medicine. The intense crush of life spawns unique chemicals such as kainic acid, collected from reef organisms in Japan and Taiwan, used as a diagnostic chemical to investigate Huntington's chorea, a rare, but fatal, disease of the nervous system. Other reef organisms generate chemicals useful for cancer and AIDS research. Corals themselves produce a natural sunscreen, which chemists are developing to market, and their porous limestone skeletons are promising for bone grafts in humans.

For the 109 countries whose shores are lined with more than 60,000 miles of reefs, the ecosystem is a national asset. Reefs provide immeasurable service by protecting coastal lands from the erosive forces of the sea. More than two-thirds of the world's sandy shorelines are thought to be eroding. The results of losing reefs can be seen in Tanzania, where formerly protected resort beaches are eroding at a rate of more than five yards per year. The bill for replacing these self-repairing breakwaters can run into the hundreds of millions, depending on the technology used.

Besides protecting coastlines, reefs also help form the idyllic white sand beaches and light turquoise lagoons that draw tourists to the tropics. Coastal tourism is the world's to the fastest growing industry, worth over $7.000,0010,000 annually in the Caribbean, the tourist Mecca. Other regions have seen coastal visitors double and triple in numbers over the last decade. In Southeast Asia, more than 110 existing and planned tourist sites are found along the coasts, many of which are reef-lined.

Locally, reefs are saltwater supermarkets of food and raw materials, especially for traditional coastal and island people. Pacific islanders receive up to 90% of their animal protein from reef fish, and people in Southeast Asia, the Caribbean, and parts of South Asia and East Africa derive a significant portion of the protein in their diets from the fish that live in these ecosystems.

Healthy reefs are thought to be among the most productive fisheries in the oceans--10-100 times higher per unit area than the open ocean. The total catch from reefs is estimated at 4-8,000,000 tons per year, approximately one-tenth of the fish caught for use as human food. According to John McManus, a marine scientist doing research at the University of the Philippines Marine Science Institute in Bolinao, coral reefs may account for up to 20-25% of the fish catch of developing countries.

Beyond their considerable value as a natural resource, reefs have intrinsic worth as one of the oldest living, thriving ecosystems. Mankind rapidly is extinguishing these intricate works of evolution that it is only beginning to understand.

Charles Darwin's five-year voyage on the HMS Beagle took him to the South Pacific, where he especially was interested in atolls, low islands that form on exposed reef. From their telltale circular shape with a lagoon in the center, he deduced that atolls were reefs that had formed...