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Study: Warming Causing Frog Extinctions

IN a forewarning to what could become the fate of humankind, a team of experts last week released a study providing substantial evidence that global warming spurs a fatal skin disease that threatens amphibians and has already extinguished two frog species Costa Rica.


The results of the research, led by scientist J. Alan Pounds, a naturalized Costa Rican of U.S. descent who works at the Monteverde Cloud Forest Preserve, on the Costa Rican mountaintop community of the same name, were published Jan. 12 in the famed British scientific journal Nature.


Costa Rican biologists Robert Puschendorf and Arturo Sánchez-Azofeifa, the latter who now resides in Canada, contributed to approximately three years of research leading up to an explanation for the extinction of two Monteverde frog species, the golden toad (Bufo periglenes) and the harlequin (Atelopus sp.), in the late 1980s (TT, June 3, 2005).


According to the study, approximately 67% of the estimated 110 species of Atelopus in Central and South America also became extinct in the 1980s and 1990s as a result of global warming.


A team of Latin American experts and three other Monteverde residents – renowned British photographer Michael Fogden, Karen Masters, a U.S. biology instructor at the Council for International Education Exchange, and Bruce Young, an U.S. zoologist who works for the U.S.-based nonprofit conservation group NatureServe – collaborated with the study.


The research concludes that global warming – which is unrelated to depletion of the ozone layer – heightens cloudiness, a condition that worsens the deadly fungus that plagues amphibian skin, according to Puschendorf.


The biologist explained that in addition, global warming produces cooler daytime temperatures and warmer nocturnal temperatures.


These boost the development of a type of fungus known as chytrid (Batrachochytrium dendrobatidis), whose optimal growth is between 17-25 degrees Celsius (63-77 degrees Fahrenheit), according to a statement from NatureServe.


“If a day is clear, they (amphibians) can rid themselves (of the fungus). If it’s always cloudy, solar radiation does not shine through to heal their skin,” Puschendorf told The Tico Times.


Puschendorf, who will soon depart to Australia to complete doctoral studies in biology, explained that at night, the cloud cover impedes solar radiation from escaping into the atmosphere, producing the increased warmth.


The study analyzed records of sea surface and air temperatures, showing that harlequin frog species are disappearing as global warming increases, according to the NatureServe statement.


HOWEVER, The New York Times last week reported that other experts doubt the conclusiveness of the study.


Cynthia Carey, an amphibian disease expert from the University of Colorado, told The New York Times that Pounds’ work does not “offer anything beyond circumstantial evidence.”


“It is difficult to prove cause and effect on the ground where multiple factors interact in complex ways,” she told the U.S. daily. Stephen H. Schneider, a Stanford climate expert who has worked with Pounds before, said although the work is significant, “uncertainties remained.”


“It’s like anything else that’s complex,” he told The New York Times. “When you’re in the early phases of learning you look for multiple lines of argument, and when they converge with basic theory, you increase your confidence in a connection.”


POUNDS, however, has issued a call for immediate action to stop global warming. “Disease is the bullet killing frogs, but climate change is pulling the trigger,” he told NatureServe, highlighting that “Global warming is wreaking havoc on amphibians, and will cause staggering losses of biodiversity if we don’t do something fast.”


Puschendorf expressed concern that what is happening to frogs could eventually happen to people. He said global warming might worsen certain diseases among humans, such as dengue, a mosquito-borne disease that strikes Costa Rica mostly during the rainy season.


Last year, dengue cases here soared, rising to more than 36,000 cases of classic dengue and 51 cases of hemorrhagic dengue – a more severe form of the disease by the end of the year.


Logging the country’s first two hemorrhagic dengue deaths since 1999, dengue cases outnumbered the stats for 2004 by 300% during the month of October (TT, Dec. 23, 2005).



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