For the first time, researchers have identified a direct link between global climate change and local factors that cause the death of amphibian eggs in the wild, according to a paper to be published in the 5 April issue of the journal Nature.
Scientists have been trying to determine why amphibian populations worldwide have been declining at alarming rates since the late 1970s, but their research has pointed to a confusing variety of causes. Now Joseph Kiesecker, professor of biology at Penn State, reports the research team he leads has shown that global warming causes changes in rainfall patterns, causing stress in moisture-sensitive amphibians, leaving them susceptible to a variety of pathogens. The specific stresses and specific resulting causes of death depend on the specific conditions in the animals' local habitat.
Kiesecker's team found a direct link between the Southern Oscillation Index, which tracks temperature fluctuations including the El Nio warming cycles in the South Pacific, and the amount of rain or snow in Oregon's Cascade Mountains. Other members of the team include Andrew R. Blaustein and Lisa K. Belden, of Oregon State University.
"For over 10 years, we have been collecting data at a number of sites in the Cascades, 4,000 to 7,000 feet above sea level, where there are large breeding populations of western toads," says Kiesecker, whose team backpacks for 10 miles to reach some of the remote sites. The researchers work in tents for weeks to build their experimental devices, which include boxes they designed to anchor the toad eggs at different distances below the surface of the lake in order to learn whether a thicker blanket of water better protects the eggs from the damaging effect of ultraviolet radiation. "We have found that water levels are shallower during years when there is less snow, which exposes the eggs to more ultraviolet light and makes them susceptible to disease outbreaks," says Kiesecker.
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Contact: Barbara K. Kennedy
science@psu.edu
814-863-4682
Penn State
4-Apr-2001