Posted: October 26, 2007
Frogs and toads were a prominent part of the local ecosystem when J. Alan Pounds went to the cloud forests in Costa Rica more than 25 years ago as a field assistant and aspiring biologist. Thousands of golden toads, strikingly luminescent creatures that obviously don't rely on camouflage for protection, could be seen during annual breeding congregations. "It was one of the truly great wildlife spectacles of new world tropics," Pounds said. "The sad part of the story is that the golden toad has vanished."
Now a resident scientist at the Monteverde Cloud Forest Preserve, Pounds gave his talk on "Where Have All the Frogs Gone?" at Mount Holyoke on October 24 by invitation of the McCulloch Center for Global Initiatives.
In 1987, populations of golden toads and other equally abundant species of amphibians crashed, in many cases within a period of months, to the point where they are now feared to be extinct. At the time global warming was a new and somewhat fuzzy concept for Pounds. In the early 1990s, he said, "I started analyzing these patterns and their relationship to climatic changes we were seeing." In 1997, he attended a workshop at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, where he met biologists from other parts of the world seeing similar phenomena.
Pounds and two colleagues published their first paper in the journal Nature in 1999. They raised the specter that changes in the earth's climate might explain the synchronous population crashes of 20 of the 50 frog and toad species in their study area. The editors of Nature, a preeminent scientific journal, wouldn't allow the term "global warming" for fear of sounding "apocalyptic," Pounds said after his lecture. A subsequent article published last year has the term in its headline, "Widespread Amphibian Extinctions from Epidemic Disease Driven by Global Warming." In it he and more than a dozen coauthors warn that not only are amphibians threatened by accelerating climate change but that it could trigger the extinction of many species by mid century. "Changing disease dynamics," thereby creating conditions under which deadly pathogens thrive, they argue, could seriously erode biodiversity.
"It is becoming increasingly clear that global warming is a real problem that we have to all be concerned about and do something about," Pounds said. "It is not just rising temperatures, it is patterns of precipitation, atmospheric moisture, winds, cloud behavior, and other things we could add to the list."
The research leads Pounds to believe with a high degree of certainty that fungi known as chytrids are an important culprit for the crashes in various frog and toad populations. Moreover, these fungi took off due to several consecutive years of elevated ocean surface temperatures. He was able to correlate the timing of the die-offs with data on rising average temperatures generated by the Intergovernmental Panel on Climate Change (IPCC). "Eighty percent of the disappearances tended to follow relatively warm years," he said.
The mechanisms for how rising overall temperatures leading to shifting moisture patterns affect local ecosystems are still a topic of study. For instance, Monteverde, where Pounds does his research, has seen longer dry spells interspersed with wetter periods, he said, explaining that the duration of particularly moist or dry spells can be as important as the total amount of rainfall. Small shifts in microclimates can have devastating effects, he said.
Species inhabiting a larger range have a better chance of overcoming insults to their environment, noted Pounds, adding that the problem is, "we are changing the climate very quickly." He has looked at the harlequin frog genus, which encompasses about 110 known species across Central and South America, determining that as many as two thirds of these species have vanished. "The losses we are seeing portend a mass extinction in the making," said Pounds. "Unless we take steps to stabilize climate it is likely we are going to see the loss of hundreds of thousands of species of plants and animals."
Though primarily a scientist Pounds believes the time for political action is overdue. "We should all be speaking out because we've moved beyond the stage where doing something about global warming is simply a precaution," he said. "There are already changes in living systems that are telling us that we are seeing impacts that are very important for biodiversity and for humans as well."
Pounds, a naturalized Costa Rican citizen who is originally from Arkansas, has been living in the Monteverde Cloud Forest long enough to observe a transformation that goes beyond the plants and animals he studies. "I stayed long enough so that I could see the change," he said. "I can look out my window these days and see a totally different set of species than were there 20 years ago."
His talk was part of the launch next year of a study abroad program initiated by Mount Holyoke and Goucher College in Baltimore to send students to the Monteverde Institute, where they will have access to educational resources such as those offered by the Monteverde Cloud Forest Preserve.