Invasive Plants in PNW Ecosystems
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A Summary of Herbicide Effects to Wildlife.Shawna L. Bautista, USDA Forest Service, Pacific Northwest Region, PO Box 3623, National herbicide risk assessments and peer-reviewed literature were used to characterize effects of herbicide use on free ranging wildlife present on National Forests in Oregon and Washington. These analyses significantly modified some of the typical thresholds of concern used to evaluate risk to wildlife. These modifications added a degree of caution to account for the value placed on wildlife species in the Pacific Northwest and the uncertainty inherent to the risk assessment process. The results of these analyses found that several commonly used herbicides may pose some unexpected risks to certain groups of wildlife that have not been reported before, most notably for grass-eating or insect-eating mammals and birds. 2,4-D exceeded these thresholds of concern in many scenarios. Triclopyr and dicamba pose significant risks to some animals in certain circumstances, including adverse affects to reproduction and mortality. Surprisingly, even glyphosate posed risks of adverse effects in some scenarios. The newer herbicides, including acetolactate synthesis (ALS) inhibitors, appear to pose very low risk to free-ranging wildlife, based on data currently available. This information was used to develop standards for herbicide use across the Pacific Northwest region of the Forest Service.
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