In the summer of 2002, fishermen, scientists and scuba divers began noticing a troubling pattern around Australia's Great Barrier Reef. Its brilliant colors were turning ghostly white. Corals—the tiny, soft-bodied organisms whose secretions collectively form sturdy reefs—bleach when they are about to die. They die when the temperature of the ocean water increases by as little as two or three degrees.
Great Barrier Reef, a 1,600-mile-long network of coral so vast it can be seen from space, provides shelter and food to more than 1,500 species. It's also central to Australia's economy, supporting a $1 billion fishing industry and attracting 2 million visitors a year who generate $4 billion in economic activity.
Some 54 percent of Great Barrier's reefs bleached that summer. The water was warmed primarily by the episodic climate phenomenon of El Niño, and after the El Niño currents subsided, most of the reef recovered. But that incident, and another bleaching four years earlier, set off alarm bells for marine scientists who fear the gradual increase in ocean temperature from global warming. "We may be witnessing the beginning of a slow-motion degradation of the reef that will only get worse in coming decades," Terry Done, a researcher with the Australian Institute of Marine Science, told the Sydney Morning Herald.
Global ocean temperatures have risen 1.3 degrees Fahrenheit since the late 19th century, according to the Intergovernmental Panel on Climate Change.
Rarely seen before the 1970s, coral bleaching now occurs fairly regularly in the Pacific, the Persian Gulf, the Indian Ocean and the Caribbean Sea. "The trends are not good. The long-term outlook is pretty negative right now," says Kacky Andrews of the National Oceanic and Atmospheric Administration. "There's no ifs, ands or buts about it: Climate change is the primary threat."
Already, the world has lost 19 percent of its original coral reefs, according to a survey published in the journal Science in 2008. Another 35 percent are under threat of loss in the next 20 to 40 years. As oceans continue to warm, half the corals on earth could be gone by 2050, before today's high school students have retired. A team of British researchers has considered a drastic plan: freezing reef samples in labs—a kind of Noah's Ark to save marine biodiversity—in case they are extinct in the wild by the end of this century.
