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The Providence Journal

Ocean Acidification Will Cost Us Dearly

Andrew Sharpless

Enjoy serving shrimp, oysters or crabs during your holiday meals? Then you should pay heed to the big climate-change meeting opening next Monday in Copenhagen. What nations decide there could determine if our ocean will continue providing tasty shellfish - or instead become part of a perilous chemistry experiment that could ravage valuable fisheries and coral reefs.

The problem, strange as it may seem, is that the ocean is doing a wonderful job of slowing down global warming. Every day, it removes nearly 30 million metric tons of carbon dioxide - the main warming gas - from the atmosphere. That's nearly twice what U.S. power plants, cars and factories spew daily into the sky. So we owe the ocean a big thanks for putting a brake on climate change and giving us time to find solutions.

Unfortunately, that help comes at a steep price. When carbon dioxide in the air mixes with seawater, a chemical reaction creates a compound called carbonic acid. In the ocean, however, "acidification" is bad news for shellfish and corals. That's because as acidification increases - and it is increasing rapidly - the process locks up the carbonate molecules these creatures need to build their shells and stony skeletons.

So far, climate negotiators have paid scant attention to ocean acidification. That needs to change in Copenhagen.

Already, scientists say the oceans are 30 percent more acidic than they were just 250 years ago. That's a disturbingly rapid shift, perhaps 100 times faster than anything Earth has had during the last 200,000 years. And if we don't act soon to curb emissions, acidity could double by the end of the century, making our seas more acidic than they've been in 20 million years.

Scientists are just beginning to fully understand the consequences of this massive chemistry experiment. Studies, for instance, suggest that adult fish and shellfish might survive more acidic waters but their eggs and larvae may not. So, over time, these organisms would become "dead species walking" - seemingly fine but reproductively doomed.

Other research predicts that some ocean waters could become acidic enough to dissolve the shells of the tiny creatures that form the critical base of the marine food chain. These "pteropods" are a favorite food of pink salmon, and help sustain giant whales.

One of the first victims of acidification, however, will be the world's hard corals. Tiny coral polyps build their monumental, dazzling reefs by manufacturing tons of limestone. But the corals won't be able to keep up their masonry if acidification continues. In fact, several studies have concluded that if emissions aren't curbed, virtually all warm-water reefs could stop growing and start crumbling to rubble by the middle to end of this century. Among the potential U.S. casualties: reefs off Hawaii, Florida and the Gulf Coast that serve as backbones for some of the planet's richest habitats. And if the reefs go, so could iconic species that are part of America's cultural - and culinary - heritage, such as snapper, grouper and spiny lobster.

Such losses would have enormous social and economic consequences. Reefs support tourism and global fisheries worth billions of dollars annually, and more than 100 million people rely on them for their food and livelihood.

Still, you might be surprised by the names of the nations most vulnerable to ocean acidification. Japan, France and the United Kingdom, for instance, took the top three spots in a forthcoming risk analysis by Oceana scientists. In making the list, they considered each nation's seafood catch and consumption, the size of its coral reefs and the sensitivity of its coastal waters to acidification. They found that more than a third of the world's population lives in the 15 most vulnerable nations - including the 8th-ranked U.S. and 13th place China.

Luckily, the list also reveals that many of the most vulnerable nations are also in the best position to do something to prevent acidification. Like China and the U.S., they are leading emitters of greenhouse gases - and in Copenhagen, they can help put the world on the path to healthier oceans by forging ahead with a global agreement to reduce emissions.

The goal must be ambitious. To protect coral reefs, for instance, scientists say we must eventually reduce atmospheric carbon-dioxide levels to 350 parts per million or less. Unfortunately, we are already at a worrisome level of 385 ppm. So time is running out for action to roll back acid-forming emissions.

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Andrew Sharpless is chief executive of Oceana, an international ocean-conservation group.

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