Pesticides are involved with population declines of amphibians in the California Sierra Nevadas.

Donald W Sparling,Gary Fellers,Laura Mcconnell

doi:10.1100/tsw.2001.36

Abstract

Several species of frogs and toads are in serious decline in the Sierra Nevada Mountains of California. These species include the threatened red-legged frog (Rana aurora), foothill yellow-legged frog (R. boylii), mountain yellow-legged frog (R. muscosa), Cascades frog (Rana cascadae), western toad (Bufo boreas) and Yosemite toad (B. canorus). For many of these species current distributions are down to 10% of historical ranges [1,2]. Several factors including introduced predators [3,4,5], habitat loss [2], and ultraviolet radiation [6] have been suggested as causes of these declines. Another probable cause is air-borne pesticides from the Central Valley of California. The Central Valley, especially the San Joaquin Valley, is a major agricultural region where millions of pounds of active ingredient pesticides are applied each year (http://www.cdpr.ca.gov/dprdatabase.htm). Prevailing westerly winds from the Pacific Coast transport these pesticides into the Sierras [7,8].

Highlights

Several species of frogs and toads are in serious decline in the Sierra Nevada Mountains of California
A study coauthored by scientists from the U.S Geological Survey and the U.S Department of Agriculture and currently in press in Environmental Toxicology and Chemistry, shows that amphibians in the Sierra, even in National Parks, are being exposed to these pesticides and that this exposure is causing neurological effects
The study shows that Pacific treefrogs (Hyla regilla) collected from Sequoia and Yosemite National Parks and the Lake Tahoe Basin had lower whole body cholinesterase activity (ChE) than those from coastal reference sites (p = 0.0001) and that those at Sequoia NP, downwind from the San Joaquin Valley, had lower ChE than those at Lake Tahoe, downwind of the less intensely agricultural Sacramento Valley

Summary

Introduction

Several species of frogs and toads are in serious decline in the Sierra Nevada Mountains of California. Another probable cause is air-borne pesticides from the Central Valley of California.

Results

Conclusion