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Ocean animals face a mass extinction from climate change

Many species are slowly suffocating as oxygen leaches out of the seas.

Many species are slowly suffocating as oxygen leaches out of the seas. "If we're not careful, we're headed for a future that I think to all of us right now would look quite hellish. ... It's a very important wake-up call."The world has already warmed more than 1 degree Celsius since the preindustrial era, and last year the oceans contained more heat energy than at any point since record-keeping began six decades ago.

Many are fleeing northward in search of cooler waters, causing "Extirpation" - or local disappearance - of once-common species. Using climate models that predict the behavior of species based on simulated organism types, Deutsch and Penn found that the number of extirpations, or local disappearances of particular species, increases about 10 percent with every 1 degree Celsius of warming. Penn and Deutsch's research revealed that most animals can't afford to lose much more than 50 percent of their habitat - beyond that number, a species tips into irreversible decline. The danger of warming is compounded by the fact that hotter waters start to lose dissolved oxygen - even though higher temperatures speed up the metabolism of many marine organisms, so that they need more oxygen to live.

The ocean contains just one-sixtieth as much oxygen as the atmosphere, even less in warmer areas where water molecules are less able to keep the precious oxygen from bubbling back into the air. The heating of the sea surface also causes the ocean to stratify into distinct layers, making it harder for warmer, oxygenated waters above to mix with the cooler depths. Most species can expend a bit of extra energy to cope with higher temperatures or adjust to rising acidity. Even some corals have found ways to keep their calcium carbonate skeletons from eroding in more acidic waters. A recent report from the Intergovernmental Panel on Climate Change found that warming has already contributed to the disappearance of at least 400 species.

A separate U.N. panel has found that about 1 million additional species are at risk of extinction as a result of overexploitation, habitat destruction, pollution and other human disruption of the natural world. A comprehensive new assessment published Wednesday in the journal Nature showed that more than 20 percent of reptile species could vanish. The creation of national parks on islands where the gecko is found helped avert habitat loss that could have doomed the species. "If you have multiple threats ... working together, often even when you think one of them is under control, then the other one turns out to be even more of a threat," Hedges said.

Source : Washington Post

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