The Washington Post
January 8, 2004 Thursday
Final Edition
SECTION: A Section; A01
LENGTH: 952 words
HEADLINE: Warming May Threaten 37% of Species by 2050
BYLINE: Guy Gugliotta, Washington Post Staff Writer
BODY:
In the first study of its kind, researchers in a range of habitats including
northern Britain, the wet tropics of northeastern Australia and the Mexican
desert said yesterday that global warming at currently predicted rates will
drive 15 to 37 percent of living species toward extinction by mid-century.
Dismayed by their results, the researchers called for "rapid implementation
of technologies" to reduce emissions of greenhouse gases and warned that the
scale of extinctions could climb much higher because of mutually reinforcing
interactions between climate change and habitat destruction caused by
agriculture, invasive species and other factors.
"The midrange estimate is that 24 percent of plants and animals will be
committed to extinction by 2050," said ecologist Chris Thomas of Britain's
University of Leeds. "We're not talking about the occasional extinction -- we're
talking about 1.25 million species. It's a massive number."
The study marks the first time scientists have produced a global analysis
with concrete estimates of the effect of climate change on habitat. Previous
work -- much of it by the same researchers -- focused on smaller regions or
limited numbers of species.
Thomas led a 19-member international team that surveyed habitat decline for
1,103 plant and animal species in five regions: Europe; Queensland, Australia;
Mexico's Chihuahuan Desert; the Brazilian Amazon; and the Cape Floristic Region
at South Africa's southern tip. The study is being published today in the
journal Nature.
The five regions encompass 20 percent of Earth's surface and "include a fair
range of terrestrial environments," Thomas said in a telephone interview from
Leeds. "Obviously, it would be valuable to expand the scope, but there's no
reason to think that doing so would change our results tremendously."
Researchers said the wide geographical scope also overcame outside factors
that might affect a single region only. "A prolonged drought might cause one
instance of a dieback" but be offset by changes elsewhere, acknowledged climate
change biologist Lee Hannah, who worked in South Africa. "When you see the
broader context, the regional blips drop out."
Although there is little dispute that Earth's temperature is rising, debate
over the reasons and speed of change remains contentious. Still, most scientists
accept that much of the warming is caused by the cumulative effects of
human-produced emissions of carbon dioxide and other "greenhouse gases" -- from
power plants and other industries -- that trap and hold heat in the atmosphere.
One skeptic, William O'Keefe, president of the George C. Marshall Institute,
a conservative science policy organization, criticized the Nature study, saying
that the research "ignored species' ability to adapt to higher temperatures" and
assumed that technologies will not arise to reduce emissions.
Climatologists have developed models that describe the temperature changes
that specific regions have undergone over periods of as long as 30,000 years.
The Nature study used U.N. projections that world average temperatures will rise
2.5 to 10.4 degrees Fahrenheit by 2100.
The trick for the study, Thomas said, was to marry the maps of projected
climate change in particular regions with maps describing the habitat --
especially the climate needs -- of plants and animals in the same area.
For this, "we needed to get the people together who knew where the species
lived," Thomas said. These were the conservationists on the research team --
ecological experts who study extinctions by looking at traditional culprits:
destruction of habitat through agriculture, industry or human settlement;
invasive species shoving aside native plants and animals; and hunting and
extermination of pests.
"Obviously, plants and animals depend on climate for survival, but we figured
that if we protect them in place, they would be all right," Hannah said in a
telephone interview from his home in California. "But now we realize that we
have to take care of them not only where they are now, but where they might have
to go."
The team calculated the effects of climate change on extinctions by using
what ecologists J. Alan Pounds and Robert Puschendorf, in an article
accompanying the study, called "one of ecology's few ironclad laws" -- that
shrinking habitat supports fewer species.
The study considered a range of possibilities based on the ability of each
species to move to a more congenial habitat to escape warming. If all species
were able to move, or "disperse," the study said, only 15 percent would be
irrevocably headed for extinction by 2050. If no species were able to disperse,
the extinction rate could rise as high as 37 percent.
"Reality, of course, will fall somewhere in between," Thomas said.
As an example, he cited Britain's comma butterfly, a robust flier that
hopscotched 160 miles north from 1982 to 1997, feeding all the way -- in its
caterpillar phase -- on stinging nettles. By contrast, the silver-studded blue
butterfly needs to move north but cannot, because it needs lowland heath to
survive, and the gaps between patches of habitat are too large for this
weak-winged flier to overcome. As a result, "it has continued to decline,"
Thomas said.
Pounds, speaking by telephone from his office in Costa Rica's Monteverde
Cloud Forest Preserve, called the study's results "ironclad" and "if anything,
too conservative." The adverse effects of natural roadblocks would be compounded
by "interaction with other changes" such as agriculture, human settlement or
invasive species, he said.
"There are different ways you can lose area," Pounds said. "One is to have
the habitat directly destroyed. Climate change does the same thing."