The Bufo periglenes,
the golden toad of Costa Rica, vanished from its habitat in 1987 in the
Monteverde Cloud Forest Preserve in Costa Rica.
It is the first
animal species credited with being driven to extinction by climate change.
Biologists
do not expect it to be the last. Camille Parmesan, a professor of conservation
biology at the University of Texas, called the golden toad "a very rare
prized endangered species, which has always been very restricted, only
ever known from Monteverde, and that's been linked with climate change."
"One extinction
of an entire species has been solidly linked to climate change," Parmesan
told United Press International, "and lots and lots of population extinctions."
The fate of
the golden toad was tracked by J. Alan Pounds, a biologist at the Monteverde
Cloud Forest Preserve and Tropical Science Center in Costa Rica.
Pounds also
wrote in Froglog, the newsletter of the Declining Amphibian Populations
Task Force of the World Conservation Union's Species Survival Commission,
that "Twenty species of frogs and toads have been missing from a 30 square
kilometer study area throughout the 1990s."
That represents
about 40 percent of the frog and toad species in the area.
Amphibians have
undergone a mysterious worldwide decline for at least the past 20 years.
A number of
hypotheses have been offered, including climate change, disease -- especially
the chytrid fungus -- pesticides, introduced predators, illegal collection
of frogs and other yet-to-be-determined culprits.
Pounds points
the finger at climate change for the loss of the golden toad -- and perhaps
for the other 20 cloud forest species.
"Climate may
have been a key factor in the declines," he wrote.
"Although there
is growing evidence that epidemic disease has been an important proximate
cause of mortality, different pathogens have been implicated in declines
on different continents. The patterns suggest the existence of a common
denominator, and global warming could fill this role through various mechanisms."
Monteverde has
seen a trend toward more severe dry seasons.
The clouds in
the Monteverde Cloud Forest are caused when moisture-laden trade winds
rise up the Caribbean slope of the mountains and cool. Pounds believes
the atmospheric warming has "raised the mean height at which condensation
begins and thereby has increased the average altitude at the base of the
cloudbank. ...
Local temperature
trends, viewed in relation to the modulating effects of clouds, are consistent
with global warming and this condensation-height model."
There are other
indicators this hypothesis is correct. Birds usually found only at lower
altitudes, like toucans, now colonize farther up in the mountains.
"We have had
one species extinction that is solidly linked to climate change," Parmesan
said, and added there likely will be more.
Global temperature
averages are expected to increase between 2 and 6 degrees Celsius over
the next century, according to the
Intergovernmental Panel
on Climate Change.
The impact of
that change on the biology remains uncertain.
A recent study
sponsored by the IUCN-The World Conservation Union reported between 15
percent and 37 percent of species sampled in six critical world ecological
regions could become extinct by the year 2050 because of their inability
to adapt to the changing climate.
The report found,
"Climate change could rival habitat loss and other major threats to land
animals and plants."
Parmesan said
she felt there were problems with the study, including the fact the authors
improperly extrapolated results from climate models and used too-precise
numbers in the summary.
"This is not
a great paper," she told UPI. "I'm not sorry it got published, and I think
the authors did a good job up to the point of summarizing. All the individual
facts in there are fine, but when they came up with their abstract, I don't
know what they were thinking.
"The state of
the science is still very young in this field," Parmesan said. "What the
paper reports are these widely varying estimates. In the details, they
put all the caveats. But in the abstract they put these exact numbers in.
Everyone's been
jumping on that, and they're right to jump on it, because there is no way
that this approach at the stage of the science now can give you exact numbers."
The study's
prediction of additional extinctions seems to be borne out by accumulating
events.
Parmesan said:
"If you start going into subspecies ... like the Chino checkerspot butterfly
was a listed subspecies... I argued during the recovery plan that it was
being driven to extinction by the combination of climate change and habitat
loss."
The northern
part of the range was Los Angeles and San Diego, where most of its habitat
was lost. The southern part of the range was in Mexico, where the populations
have disappeared "even though the habitat looked beautiful.
Climate change
has clearly caused problems for species that were already in difficulty,"
she said.
Other species
of specialized habitats and low numbers face difficulties. The Arctic fox,
for instance, has become very restricted in habitat.
As the climate
has warmed, the red fox has expanded its range northward and the Arctic
fox can't compete with it fellow
species.
The collapse
of the Atlantic cod fisheries was not caused by climate change.
It was caused
by overfishing but its failure to recover since fishing was stopped may
be attributable to ocean warming in its habitat that hinders recruitment
of juveniles.
Parmesan and
colleague Gary Yohe, of Connecticut's Weslayan University, published a
paper in Nature last year that found a "diagnostic fingerprint" for 279
species of plants, animal, fish and invertebrates for which they found
a "very high confidence that climate change is already affecting living
systems."
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Copyright 2004 by United
Press International.
All rights reserved.
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