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 / Updated  / Source: NBC News

Global warming, if left unchecked, could eventually push 1 out of every 6 species on Earth into extinction, a new study projects. In a report published Thursday in the journal Science, University of Connecticut ecologist Mark Urban analyzed 131 peer-reviewed studies on species that used various types of computer simulations. He found a general average extinction rate for the globe: 7.9 percent, or about 1 out of every 13 species. That's an average for all species, all regions, taking into consideration various assumptions about future emission trends of man-made greenhouse gases. By the end of the century, in a worst-case scenario if world carbon emission trends continue to rise, 1 in 6 species will be gone or on the road to extinction, Urban said. That's higher than the overall rate because that 7.9 percent rate takes into account some projections that the world will reduce or at least slow carbon dioxide emissions.

The extinction rate calculation doesn't mean all of those species will be gone; some will just be on an irreversible decline, dwindling toward oblivion, Urban said. "It's a sobering result," he said. The projected extinction rate changes with time and how much warming there is from the burning of coal, oil and gas. At the moment, the extinction rate is relatively low, 2.8 percent, but it rises with more carbon dioxide pollution and warmer temperatures, Urban wrote. What happens is that species tend to move closer to the poles and up in elevation as it gets warmer, Urban said. But some species, especially those on mountains such as the American pika, run out of room to move and may die off because there's no place to escape the heat, Urban said. It's like being on an ever-shrinking island.

Still, researchers said the extinction from warming climates is dwarfed by a much higher extinction rate also caused by man: Habitat loss. A large extinction is going on, and for every species disappearing for natural causes, 1,000 are vanishing because of unnatural man-made causes, said biologist Stuart Pimm of Duke University, who was not affiliated with the research.



— The Associated Press and NBC News contributed to this story