Global warming may already be a killer

Earth’s rising temperatures may be a precipitating factor in the extinctions of dozens of tropical frog species, according to new research.

CROAKING? This harlequin frog belongs to a group of species that is rapidly going extinct in Central and South America. F. Brem

At least 110 species of harlequin frogs once lived in Central and South America, but two-thirds of them went extinct in the past 2 decades. Scientists have puzzled over these and other amphibian disappearances in seemingly pristine areas.

Years ago, scientists found that chytrid fungus (Batrachozchytrium dendrobatidis) had infected many dead frogs found in tropical regions (SN: 2/26/00, p. 133: New frog-killing disease may not be so new). In a new study, J. Alan Pounds of the Monteverde Cloud Forest Preserve in Costa Rica and his colleagues propose that global warming could be promoting the fungus’ growth.

Pounds’ team matched records of air and sea-surface temperatures with data on frog disappearances. The researchers found that species tended to vanish during years with the warmest average temperatures.

Warm periods enhance cloud formation over the tropics, which makes days cooler and nights warmer. Temperatures thus stay in the narrow range in which the fungus thrives, which could explain massive amphibian die-offs, says Pounds.

The researchers report their hypothesis in the Jan. 12 Nature.

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