Global warming has caused the extinction of one species of frog in an area of Costa Rica and is threatening to make extinct more than one-hundred species of frogs in the same toad family in the region, according to a new study published in the journal Nature. Scientists say it appears global warming has given rise to a toxic fungus that is wiping out the frogs in a very short period of time.
Seventeen years ago, in Costa Rica's mountainous Monteverde Forest region, the tiny, brightly-colored red, black and yellow harlequin frog could be spotted everywhere on rocks along streams. The golden toad, another frog in the same family, was also abundant, according to Alan Pounds, an ecologist with the Monteverde Cloud Forest Preserve in Costa Rica.
"In 1987, there were maybe one-thousand-five-hundred golden toads observed at the principal known breeding site. But then the next year, only a single male appeared there. And in the same year, harlequin frogs, which were so abundant along some of the streams that you had to be careful not to step on them, went to being virtually absent. And then after that, we haven't seen them," he said.
Investigators say the cause of the extinction, and 67 percent reduction of the family of toads that includes the harlequin and golden frogs, was a point-one-eight-percent increase in temperature each decade since 1975.
Drawing on an extensive database produced by 75 researchers, scientists found a clear relationship between the number of frogs deaths and temperature increase, with the most amphibians disappearing in the warmest years.
During those years, Mr. Pounds say it appears a fungus, which normally lives harmlessly on the frogs' skin, became toxic and kills the amphibians. Under normal circumstances, the fungus is kept in check by the temperature extremes of the mountainous tropical forest regions. But milder temperatures, brought about by such factors as deforestation, have caused the deadly fungus to thrive, leading to the frogs' demise. "So the disease is the bullet killing frogs. The climate is pulling the triggers," he said.
As further proof that global warming is adversely affecting the frogs, Mr. Pounds says there are no extinctions of harlequin frogs in the lowlands where it is warm all the time.
Mr. Pounds says the study provides proof that global warming is creating disease where none existed and that should raise concern. "You can't keep changing ecosystems and expect our own life support system to be viable. So, you have to take notice and do something about it," he said.
Researchers believe similar extinction processes are under way in other parts of the world, and there are efforts to identify them and their causes.