Black band disease spreads across a colony of Favia speciosa at the Great Barrier Reef, Australia.
Black band disease spreads across a colony of Favia speciosa at the Great Barrier Reef, Australia. Cathie Page
White spots mark areas of disease on a coral in Little Kelso Reef, Great Barrier Reef, Australia.
White spots mark areas of disease on a coral in Little Kelso Reef, Great Barrier Reef, Australia. Cathie Page
Coral reefs around the world are in bad shape these days. But a new research paper in the journal Science says their problems may be getting worse. The paper says as much as a third of the world's coral species may now be headed toward extinction, thanks to problems ranging from destructive fishing boats to ocean waters warmed by global climate change.
Coral experts say these reefs hold 25 percent of the world's marine species. That list includes sponges, lobsters, turtles, shrimp, sharks and commercially important fish. Philip Munday, a reef expert at Australia's James Cook University, says that's why coral reefs are often called "the rain forests of the ocean."
"It's quite stunning when you get into the water on a lovely clear day and you drop down onto [healthy] reef," says Munday. "There are fish everywhere, hundreds of thousands of fish, the sort of things you almost don't see anywhere else."
Unfortunately, reefs like those are few and far between these days. And Kent Carpenter, a reef expert at Virginia's Old Dominion University, says the problems faced by these important ecosystems may be worse than a lot of experts think they are. In a new paper, he reports that a third of the world's coral species are now declining toward extinction, partly owing to increased outbreaks of coral diseases. Corals that aren't killed off by these new diseases are recovering more slowly, he reports. Some are slowly overwhelmed by ugly gobs of algae.
"I have been on several coral reefs recently that have had large clumps of algae growing on the reefs themselves," he said. "And if you pull off the algae, you see that the coral underneath them has died, because it couldn't get any sunlight."
Carpenter says sights like those are easily as ugly as the image of a thriving reef is beautiful, adding that in his opinion a global coral crisis is now in full bloom.
"This is a whole ecosystem that we potentially could be losing," he said.
That's the central message in the paper Carpenter has just published in Science. He says he prepared it with the help of coral researchers affiliated with the International Union for Conservation of Nature, a nonprofit conservation group whose scientific work is widely thought to be definitive.
The coral researchers pored through records kept at field stations near coral reefs found all over the tropics. Carpenter says the result is a so-called coral "red list" that concludes that a third of the world's coral species may be declining toward extinction. He says the researchers found some evidence of a link between coral-killing diseases and warming ocean waters. He adds that it's possible that even bigger problems will emerge if emissions of global warming gases aren't reduced soon.
For example, he says ocean waters are becoming more acidic as they soak up carbon dioxide, the main global warming gas. And while there's evidence that coral reefs can find ways to adapt to waters warmed by global climate change, there's no proof that they can cope with more-acidic oceans.
"Obviously the overarching problem that has to be solved is the [buildup of man-made] carbon dioxide in the atmosphere," he said.
Carpenter's new paper drew a lot of attention at a coral reef conference held this week in Fort Lauderdale, Fla. The paper also drew support from a different report prepared by scientists with the National Oceanic and Atmospheric Administration. That paper concluded that a quarter of the coral reefs in U.S. waters were in poor condition.
There are some rays of hope in the new coral red list. For example, it appears to show that reefs in some parts of the far Pacific are now thriving in the warming waters. And Munday, the Australian reef expert, says research conducted near the Great Barrier Reef appeared to show that when a wounded coral reef is put off limits to commercial fishermen, large numbers of big fish fill the area in a few years.
"That gives us enormous hope that these populations ... can rebound if they're given the chance to do so," he says. Munday says these programs won't protect coral reefs from problems caused by global warming. But they might help buy the reefs a little extra time.