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Scientists: Global Warming Could Kill Off Reefs By 2050

Posted on: Friday, 14 December 2007, 06:00 CST

By Elizabeth Weise

Rising carbon emissions might kill off the ocean's coral reefs by 2050, warns an international coalition of scientists.

A report in today's edition of the journal Science co-authored by 17 marine scientists in seven countries, including the USA, is the most comprehensive review so far of the threat global warming poses to coral and, by extension, many ocean species.

Burning coal, oil and gas adds carbon dioxide -- a heat-absorbing greenhouse gas -- to the atmosphere. Oceans absorb this gas, turning them more acidic. That interferes with the ability of coral, living organisms, to calcify their skeletons, and the coral begins to die.

Coral reefs act as hatcheries and nurseries for ocean fish. According to the study, coral-reef fisheries in Asia feed an estimated 1 billion people. The global economic value of coral is estimated to be $30 billion.

The world's largest reef system is the Great Barrier Reef, which stretches over 1,600 miles off the coast of Australia. More than 60% of the USA's coral reefs are found off the coasts of the Hawaiian islands.

As the planet warms, "We have created conditions on Earth unlike anything most species alive today have experienced in their evolutionary history," says study co-author Robert Steneck, a professor of marine sciences at the University of Maine. "It is now or never if we want to safeguard these marine creatures."

The scientists provide three possible scenarios:

*Best case. Carbon dioxide emissions are stabilized at today's levels of 380 ppm. Coral reefs survive mostly intact.

*Midrange. Carbon dioxide levels rise to 450-500 ppm, and the sea temperature goes up 3.6 degrees. Heat-tolerant forms of coral take over and reefs become much less diverse, with a decline in fish and other sea life.

*Worst case. Carbon dioxide levels rise above 500 ppm, and the sea temperature increases more than 5.4 degrees. The reefs crumble, and half of sea life disappears.

University of Miami marine biologist Chris Langdon says it may be a little sensational to predict a total loss of coral. But, he notes, there's no question that oceans are more acidic.

One hope is that the worst-case warming forecasts won't come true, says study co-author Ken Caldeira, a professor of global ecology at the Carnegie Institution in Stanford, Calif.

Warming "is a much easier problem to handle than, say, Hitler," he says. "We came into World War II with biplanes and came out of it with jet planes and integrated circuits. If our society actually perceived this as a threat, we could fairly easily mobilize and respond to it."

Source: USA TODAY

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