Global Warming Found to Displace Species
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By ANDREW C. REVKIN The New York Times

Global warming (news - web sites) is forcing species around the world,
from California starfish to Alpine herbs, to move into new ranges or
alter habits in ways that could disrupt ecosystems, two groups of
researchers say.


The two new studies, by teams at the University of Texas, Wesleyan,
Stanford and elsewhere, are reported in today's issue of the journal
Nature. Experts not associated with the studies say they provide the
clearest portrait yet of a biological world driven into accelerating
flux by warming caused at least in part by human activity.


Plants and animals have always had to adjust to shifting climates. But
climate is changing faster now than in recent millenniums, and many
scientists attribute the pace to rising concentrations of
heat-trapping greenhouse gases.


In some cases, species' ranges have shifted 60 miles or more in recent
decades, mainly toward the poles, according to the new analyses. In
others, the timing of egg laying, migrations and the like has shifted
weeks earlier in the year, creating the potential to separate species,
in both time and place, from their needed sources of food.


One academic not associated with the studies, Dr. Richard P. Alley, an
expert on past climate shifts who teaches at Pennsylvania State
University, said that climate had changed more abruptly a few times
since the last ice age and that nature had shifted in response. But,
he noted, "the preindustrial migrations were made without having to
worry about cornfields, parking lots and Interstates."


Citing the new work and studies of past climate shifts, Dr. Alley saw
particular significance in the expectation that animals and plants
that rely on one another were likely to migrate at different rates.
Referring to affected species, he said, "You'll have to change what
you eat, or rely on fewer things to eat, or travel farther to eat, all
of which have costs."


The result in coming decades could be substantial ecological
disruption, local losses of wildlife and extinction of some species,
the two studies said.


The authors express their findings with a certainty far greater than
in the last decade, when many of the same researchers contributed to
reports on biological effects of warming that were published by the
Intergovernmental Panel on Climate Change, the top international
research group on the issue.


The authors of one of the new Nature papers, Dr. Camille Parmesan, a
biologist at the University of Texas, and Dr. Gary Yohe, an economist
at Wesleyan University, calculated that many ecological changes
measured in recent decades had a 95 percent chance of being a result
of climate warming and not some other factor.


"You're seeing the impact of climate on natural systems now," Dr. Yohe
said. "It's really important to take that seriously."


Some butterflies have shifted northward in Europe by 30 to 60 miles or
more, with the changes closely matching those in average warm-season
temperatures, Dr. Parmesan said. The researchers were able to rule out
other factors habitat destruction, for example as causes of the
changes.


Some of these changes meshed tightly with variations in temperature
over time. Dr. Parmesan cited bird studies in Britain. There,
populations of the great tit adjusted their egg laying earlier or
later as climate warmed early in the 20th century, then cooled in
midcentury and warmed even more sharply after the 1970's.


Over all, Dr. Parmesan's study found that species' ranges were tending
to shift toward the poles at some four miles a decade and that spring
events, like egg laying or trees' flowering, were shifting 2.3 days
earlier a decade.


Around Monterey Bay in California, warmer waters have caused many
invertebrates to shift northward, driving some species out of the bay
and allowing others to move in from the south.


Authors of both new papers said they were concerned that such
significant ecological changes had already been detected even though
global temperatures had risen only about one degree in the last
century.


They noted that projections of global warming by 2100 ranged from 2.5
to 10 degrees above current levels, should concentrations of carbon
dioxide and other heat-trapping gases, which flow mainly from
smokestacks and tailpipes, continue to rise.


By comparison, the world took some 18,000 years to climb out of the
depths of the last ice age and warm some five to nine degrees to
current conditions.


"If we're already seeing such dramatic changes" among species, "it's
really pretty frightening to think what we might see in the next 100
years," said Dr. Terry L. Root, an ecologist at Stanford University
who was the lead author of one of the new studies.

The two teams of researchers used different statistical methods to
analyze data on hundreds of species, focusing mainly on plants and
animals that have been carefully studied for many decades, like trees,
butterflies and birds. Both teams found, with very high certainty, a
clear ecological effect of rising temperatures.

Several of the researchers said the effects of other, simultaneous
human actions, like urban expansion and the introduction of invasive
species, could greatly amplify the effects of climate change.

For example, the quino checkerspot butterfly, an endangered species
with a small range in northern Mexico and Southern California, is
being pushed out of Mexico by higher temperatures while also being
pushed south by growing suburban sprawl around Los Angeles and San
Diego, Dr. Parmesan said.

"The butterfly is caught between these two major human factors
urbanization in the north and warming in the south," said Dr.
Parmesan, who has spent years studying shifting ranges of various
checkerspot species.

Dr. Alley said the studies illustrated the importance of conducting
much more research to anticipate impending harms and devise ways to
maintain biological diversity, for instance with green "wildlife
corridors" linking adjacent pockets of habitat.