The connection between frog deformities and pesticides and herbicides has been reported a lot. But here is a new study by Southern Illinois University in Carbondale that shows how little it really takes to harm amphibians. Imagine there was a pool of water in a farm pond that had the presence of only a trace (0.0000000003*) of pesticide ingredient edosulfan. That would be enough to kill half of the pond’s frog population. Take the 3 and make it 8, and every frog dies. Here’s the news release explaining the study: (*Double check my decimal conversion. What I’m attempting to show is 0.3 parts per billion.)

An excerpt from the release:

The foothill yellow-legged frog is especially susceptible to the chemicals such as endosulfans, which kill by essentially overloading the nervous system and rendering breathing muscles useless. Europe and Australia each have banned the use of the chemical as a pesticide, and the U.S. Environmental Protection Agency also is studying the issue, Sparling said.

Sparling is optimistic humans can find ways to both farm on a large enough scale to feed the population and protect non-pest animals.

“To produce crops to provide for the world we have to use pesticides, and I’m not anti-pesticide,” he said. “But it’s important for us as scientists, agriculturalists and environmental protectors to make sure we continue developing pesticides that are as protective as possible of non-target animals as can be, both in the chemicals we use and application methods.”

The effects of herbicide and fertilizer runoff on amphibians in rural areas has been reported before. We’re talking about frogs that develop extra limbs and other deformities. And of course, we’re talking about frogs dying. But a University of Pittsburgh study, funded by the National Science Foundation, shows that the active ingredient in popular pesticides like some Scotts Ortho products — it’s called malathion — is preventing tadpoles from maturing because it wreaks havoc with the food chain they need to grow. Here’s excerpt from Science Centric Web site which pulls its information from the Oct. 1 issue of Ecological Applications:

Gradual amounts of malathion that were too small to directly kill developing leopard frog tadpoles instead sparked a biological chain of events that deprived them of their primary food source. As a result, nearly half the tadpoles in the experiment did not reach maturity and would have died in nature.

“The chain of events caused by malathion deprived a large fraction of the leopard frog tadpoles of the nutrients they needed to metamorphose into adult frogs,’ said study author Rick Relyea, an associate professor of biological sciences in Pitt’s School of Arts and Sciences. “Repeated applications sustained that disruption of the tadpoles’ food supply. So, even concentrations that cannot directly kill tadpoles can indirectly kill them in large numbers.”

Here’s a thoughtful article on the issue from 2005: read here.