Global warming may already be a killer.Earth's rising temperatures may be a precipitating factor precipitating factor, n the catalyst for an illness, symptom, or episode. This may not be the underlying cause of the illness, rather it is what elicits it. Also called provoking factor. in the extinctions of dozens of tropical frog species, according to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. new research. At least 110 species of harlequin frogs once lived in Central and South America South America, fourth largest continent (1991 est. pop. 299,150,000), c.6,880,000 sq mi (17,819,000 sq km), the southern of the two continents of the Western Hemisphere. , but two-thirds of them went extinct in the past 2 decades. Scientists have puzzled over these and other amphibian amphibian, in zoology amphibian, in zoology, cold-blooded vertebrate animal of the class Amphibia. There are three living orders of amphibians: the frogs and toads (order Anura, or Salientia), the salamanders and newts (order Urodela, or Caudata), and the 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). 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 tropics, also called tropical zone or torrid zone, all the land and water of the earth situated between the Tropic of Cancer at lat. 23 1-2°N and the Tropic of Capricorn at lat. 23 1-2°S. , 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.--C.B. CROAKING? This harlequin frog belongs to a group of species that is rapidly going extinct in Central and South America. |
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