WASHINGTON (AP) -
Global warming will eventually push 1 out of every 13 species on Earth into
extinction, a new study projects.
It won’t 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, that forecasted 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. That’s 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 doesn’t mean all of those species will be gone;
some will just be on an irreversible decline, dwindling toward oblivion, he
said.
“It’s a sobering
result,” Urban said.
Urban’s figures are
probably underestimating the real rate of species loss a little, said
scientists not affiliated with the research. That’s 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.
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.
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, Pimm and
Urban 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, Pimm said.
“I don’t know we’re
at the point where we can call it a mass extinction event, but we’re
certainly heading that way unless we change direction,” Urban said.
A separate study in
the same journal looked at 23 million years of marine fossils to determine
which water animals have the biggest extinction risk and where. Marine
mammals, such as whales, dolphins and seals, have the highest risk. The Gulf
of Mexico, Caribbean Sea, western Indian Ocean and Pacific Ocean between
Australia and Japan are hotspots for potential extinction, especially those
caused by human factors, the study said.
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