Seth Borenstein

WASHINGTON: Global warming will eventually push 1 out of every 13 species on Earth into extinction, a new study projects.

It wonít quite be as bad in North America, where only 1 in 20 species will be killed off because of climate change or Europe where the extinction rate is nearly as small. But in South America, the heat-caused extinction rate soars to 23 percent, the worst for any continent, according to a new study published Thursday in the journal Science.

University of Connecticut ecologist Mark Urban compiled and analyzed 131 peer-reviewed studies on species that used various types of computer simulations and found a general average extinction rate for the globe: 7.9 percent. Thatís an average for all species, all regions, taking into consideration various assumptions about future emission trends of man-made greenhouse gases. The extinction rate calculation doesnít mean all of those species will be gone; some will just be on an irreversible decline, he said.

ďItís a sobering result,Ē Urban said.

Urbanís figures are probably underestimating the real rate of species loss a little, said scientists not affiliated with the research. Thatís because Urban only looks at temperature, not other factors like fire or interaction with other animals, and more studies have been done in North America and Europe, where rates are lower, said outside biologists Stuart Pimm of Duke University and Terry Root of Stanford University.

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 species tend to move closer to the poles and up in elevation as it gets warmer, Urban said. Some species, especially those on mountains such as the American pika, run out of room and may die off because thereís no place to escape the heat, Urban said.

Still, Pimm and Urban said the extinction from warming climates is dwarfed by a much higher extinction rate also caused by man: Habitat loss. For every species disappearing for natural causes, 1,000 are vanishing because of unnatural man-made causes, Pimm said.