http://www.nytimes.com/2003/01/02/science/02CLIM.html
January 2, 2003
New York Times
Global Warming Found to Displace Species
By ANDREW C. REVKIN
Global
warming 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.
