As scientists note a worldwide decline in amphibians, they have come to consider that these animals are perhaps our environment's "canary in the coal mine," giving us early warning of environmental dangers. While no one is certain yet what is causing the decline, and multiple factors are undoubtedly involved, exposure to pesticides and herbicides is thought to play a role.
Some recent research has established the danger of a commonly used fungicide, chlorothalonil, to tadpoles. This fungicide is not only one of the most commonly used on agricultural crops, it is one that home gardeners use as well. As reported in the September 11, 2010 issue of Science News, researcher Taegan McMahon of the University of South Florida found that when the tadpoles of southern leopard and green tree frogs were exposed to low levels of chlorothalonil (levels a computer model predicted a waterway near a sprayed field will pick up from runoff, or one ten-thousandth of the exposure expected right after a field is treated), all them died within 24 hours. And when tadpoles were exposed for a month to even lower levels of the fungicide (0.0164 micrograms), they died in greater numbers than those is clean water.
Studies by another researcher, Tyrone Hayes of the University of California, Berkeley, as reported in the March 27, 2010 Science News, suggested that the herbicide atrazine, widely used in the production of corn, cotton and turf, may contribute to the decline of frogs in other ways, by feminizing male frogs and interfering with the ability of tadpoles to go through metamorphosis.
Research such as this emphasizes the importance of minimizing the use of pesticides and herbicides in our own gardens and yards, and the importance of supporting farmers who produce crops without these chemicals, by choosing to buy organically produced foods and products whenever possible.
For more information on the environmental threats facing frogs, go to: Science News.