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http://dailynews.yahoo.com/h/nm/20010404/sc/environment_climate_dc_6.html

(a href=http://dailynews.yahoo.com/h/nm/20010404/sc/environment_climate_dc_6.html)Study: Climate, Not Ozone, Hits Toad Population (/a)

Wednesday April 4 3:03 PM ET Study: Climate, Not Ozone, Hits Toad Population

LONDON (Reuters) - Declining water levels linked to climate change could lead to a long-term decline in the population of toads in the United States, a study published in Nature magazine said on Wednesday.

Previous studies had pointed to declining stratospheric ozone levels as a possible reason for a decrease in the numbers of western American toads.

A team of biologists from Pennsylvania State and Oregon State Universities found that reduced water levels caused by warmer weather exposed toad embryos in Oregon's mountains to UV-B radiation from the sun, making them more susceptible to disease. The researchers found that more than half of embryos developing in water less than 8 inches deep were killed by the pathogenic fungus Saprolegnia ferax, compared to a maximum of 19 percent killed by the fungus in water over 17.72 inches deep.

``Because the survival of amphibians is linked closely to water availability, climate changes that alter hydrology may be the precursor for similar mortality events that are believed to contribute to other population declines, including those that have been attributed to disease outbreaks,'' the study said.

Populations may be especially vulnerable where local climate is heavily influenced by the tropical Pacific Ocean.

Since the 1970s, higher sea surface temperatures in the tropical Pacific, called the El Nino Southern Oscillation, have affected the world's climate with an impact on biological communities from coral reefs to forests.

El Nino caused less snow to fall in Oregon's northern Cascade Mountains from 1990-1999, which in turn meant less water in which the western toad could lay its embryos during the spring thaw.

``If bouts of high embryo mortality occur with greater regularity and intensity, they may result in population declines,'' the study said.

-- K (infosurf@yahoo.com), April 05, 2001