Blowing in the wind: Central Valley pesticides hurt Sierra frogs

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A new study adds to the evidence that Central Valley pesticide use is jeopardizing Sierra Nevada frog populations.

In laboratory experiments, Pacific treefrog and foothill yellow-legged frog tadpoles were exposed to two commonly used agricultural insecticides, chlorpyrifos and endosulfan.

Both proved toxic. Endosulfan, used on fruits and vegetables, was especially damaging to the tadpoles, which developed abnormalities and growth problems, according to a study published in the August edition of Environmental Toxicology and Chemistry.

The yellow-legged frog, whose populations are in worse shape than the tree frog, was the more sensitive of the two.

‘Exposure to chlorpyrifos and endosulfan poses serious risk to amphibians in the Sierra Nevada Mountains,’ concluded the study authors, Donald W. Sparling of Southern Illinois University’s Cooperative Wildlife Research Laboratory and Gary M. Fellers of the U.S. Geological Survey’s Western Ecology Research Center in Point Reyes, Calif.

Wind blows pesticide residues from the San Joaquin Valley into the mountains, where the chemicals break down more slowly because of cooler temperatures.

Pesticides have been detected in the Sierra’s air, snow and water, as well as the tissues of the range’s amphibians.

-- Bettina Boxall