Roundup herbicide deadly to frog populations, according to new study

The University of Pittsburgh, where the study was conducted, used a natural setting to discover the effects of the herbicide carbaryl on frog populations, rather than controlled laboratory conditions. Carbaryl, the active ingredient in Roundup, killed 70 percent of the tadpole species studied and 86 percent of the total number of tadpoles.

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• Pitt biologist Rick Relyea found that the herbicide Roundup -- the second most commonly used herbicide in the United States -- caused major declines in tadpole population size and diversity when applied at manufacturer-recommended concentrations in outdoor tanks that simulated real ponds.
• "This is really the first discovery that something made to kill plants really can be extremely lethal to amphibians, which of course, comes as a complete surprise to a lot of people that apply Roundup," Relyea said.
• Roundup, made by Missouri-based Monsanto Co., caused a 70 percent decline in the variety of frog species in the 300-gallon tanks and an 86 percent decline in the total mass of tadpoles.
• The experiments were conducted at Pitt's Pymantuning Laboratory of Ecology, a field research station in Crawford County.
• Relyea's research, published Friday in the journal Ecological Applications, builds on his earlier studies that point to the lethal effects of the widely used pesticide carbaryl on tadpoles.
• Chemical manufacturers are required to measure the toxicity of all bug and weed killers they make, and the results must be approved by the U.S. Environmental Protection Agency.
• Most toxicology data, however, are collected under artificial conditions: Researchers slowly add a chemical to a tank of critters and find out how much is needed to kill half of them over several days.
• Relyea's experiments are among the first to study the toxicological impact of herbicides in a more natural setting that accounts for the real-world effects of predators and natural stress factors, said Yale University biology professor David Skelly, who also studies amphibians.
• "Here we have an example of how commonly used chemicals can affect entire systems," Skelly said.