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Health and Environmental Effects Research

EPA Model and Research Used To Support U.S. Court Ruling on Endangered Species Act Listing

On November 22, 2011, the 9th U.S. District Court of Appeals upheld a lower court ruling keeping the grizzly bear in the Greater Yellowstone Area on the Threatened Species list under the Endangered Species Act. The court ruled that the U.S. Fish and Wildlife Service failed to provide evidence that the ongoing decline of whitebark pine because of beetle infestations, exacerbated by climate change, was not a concern for the maintenance of grizzly bear populations. The court cited a paper co-authored by NHEERL Western Ecology Division researcher Don Phillips that demonstrated the importance of whitebark pine nuts, a high-protein and high-fat food source, in Yellowstone grizzly bear diets and quoted the authors’ conclusion that “Grizzly bear survival in the Greater Yellowstone Ecosystem is strongly linked to variation in pine-nut availability.” This paper utilized the IsoSource model developed at EPA by Dr. Phillips that estimated the importance of various foods in grizzly bear diets based on the stable isotope composition of the foods and grizzly bear tissue. This isotopic mixing model has been used widely throughout the world for such food web studies, as well as for other applications such as determining the proportions of various pollutant sources in air and water pollution studies.

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