The Sierra Nevada mountain range lies adjacent to one of the heaviest pesticide use areas in the USA, the Central Valley of California. Because of this proximity, concern has arisen that agricultural pesticides, in addition to other contaminants, are adversely affecting the natural resources of the Sierra Nevada. Transport and deposition of pesticides from the Central Valley to the Sierra Nevada has been documented, and several lines of evidence have implicated pesticide drift from the Central Valley as a causal factor in the dramatic population declines of four amphibian species in the Sierra Nevada. This study focuses on contaminants in lakes at high elevation in the southern Sierra, an area where population declines of one species, the mountain yellow-legged frog, have been dramatic. The southern Sierra is of particular interest because air pollution in the Central Valley and Sierra is generally greatest in the south, watersheds in the southern Sierra differ substantially in their proximity to the Central Valley, and the region includes large areas where the mountain yellow-legged frog has completely disappeared and other areas where large numbers remain.

"September 2001." "EPA 600-R-01-085." Cover title. Includes bibliographical references.