A weekly series by UPI examining the potential human impact on global climate change.
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BOULDER, Colo., May 31 (UPI) -- 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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Dan Whipple covers the environment for UPI Science News. E-mail [email protected]
