60-Second Earth

Corals Face Catastrophic Bleaching

This year could be a very bad year for coral reefs, thanks to warm waters as a result of El Nino and climate change. David Biello reports

In 2005 coral reefs throughout the Caribbean faced an epic heat wave—underwater. Sea surface temperatures stayed at record high levels for more than three months in some locations and as much as 60 percent of corals died as a result. Most bleached, expelling the symbiotic algae that feed them, turning once vibrant, colorful reefs into skeletal remains.

2005 was one of the hottest years in records that stretch back to 1880. This fall is even warmer at the same point in September, according to Mark Eakins of NOAA's Coral Reef Watch program. Already, bleaching throughout southeast Asia killed more than 60 percent of coral reefs in certain locations there this past May and June.

The hot weather—and hot water—has come to the Caribbean, which has seen above average sea surface temperatures since January. 

Of course, a tropical cyclone depending on where you are in the world can cool off the water fast. Satellite maps reveal the track of the recent Hurricane Earl as a wide swath of cool blue water from the Caribbean up the East Coast of the U.S.

But hoping for a hurricane is no permanent solution. Ultimately, curbing the CO2 emissions that are trapping extra heat—and acidifying the oceans, another stress on coral—is the only fix that can save the reefs.

—David Biello

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