Tule Lake and the adjacent Lower Klamath National Wildlife Refuges (TLNWR and LKNWR) serve as key spring/fall staging and overwintering areas for Pacific Flyway migratory waterfowl, with more than 89 million goose and duck use days recorded in the refuges in 1988. As many as 1,000 bald eagles (the greatest concentration in the lower 48 states) also overwinter in the Klamath Basin, utilizing these refuges for food resources. The shortnose suckers (Chasmistes brevirostris) and the Lost River suckers (Deltistes luxatus), listed as endangered in 1988, inhabit Tule Lake (in TLNWR), habitat that is currently proposed critical habitat for the suckers. The refuges are located in northern California and southern Oregon in a region of intensive agriculture. Lands on the refuges are leased to growers under requirements of the Kuchel Act, which provides for leasing of up to 22,000 acres. Crops currently grown include potatoes, onions, sugarbeets, alfalfa, and grains. More than 45 different pesticides are allowed on the lease lands, including some extremely toxic insecticides, such as the organophosphates, disulfoton and chlorpyrifos, and pyrethroids, such as permethrin and cyfluthrin. These pesticides have been allowed by Region 1's Pesticide Use Proposal Committee under a series of strict application methods, weather restrictions, and buffer zones. The objectives of this study were (1) to survey both refuges for dead or impaired wildlife, (2) to determine whether pesticide exposure is implicated in any death or impairment discovered, and (3) to investigate the source of any pesticide exposure detected.

Four morbidity and 14 Mortality incidents were recorded during the study. No documented fish/wildlife mortality or morbidity event this season was determined to be causally linked to pesticide exposure as the primary cause of death. However, all testing facility analysis of samples has not been completed as of the writing of this report. Of those vertebrate specimens for which analysis has been completed, none showed evidence of adverse pesticide exposure. Three agricultural chemical spills were noted in 2000 (two fertilizer spills, and one fertilizer/seed treatment spill). This represents a reduction in number of spills found in 1998 and 1999. Though no wildlife impacts were demonstrated to have resulted from these spills, the potential for impact does exist. Seed treatments are a concern because they are attractive to birds. Spills of both fuel and agricultural chemicals associated with irrigation pump stations are also a potential hazard as these stations are located near irrigation canals that are used by fish and wildlife and drain into Tule Lake or the Klamath River. Considering the reductions in spill finds it appears that growers are being more attentive to measures to prevent spills. According to study monitors, the most significant pesticide impact issue encountered was the net effect of poor compliance oversight by Siskiyou County Agricultural Department (SCAD) personnel. Evidence gathered from the leased lands indicates that certain activities that may pose risk to human health and the environment were routinely overlooked.

Learn More by Reading the Full Report:Hawkes, T., Merrall, E., Giovonis, D., Pesticide Impact Assessment in Tule Lake and Lower Klamath National Wildlife Refuges, USFWS. Klamath Basin Refuges. 2000.

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