ACC and its Impacts on Grizzlies in Yellowstone

The US Fish and Wildlife Service is likely to remove the Yellowstone grizzly bear (ursus arctos) population from the endangered species list, which gives federal management and protection through the Endangered Species Act. This action would return the grizzlies to state management, even in light of the fact these agencies have already indicated that they would immediately start sport hunting seasons on the bears, despite very limited evidence of increased population.

The scientific evidence used to justify the removal of the Yellowstone grizzly from ESA protection is based on range expansion, not verifiable increases in population. Environmentalists and wildlife advocates argue that range expansion is not the same as growing population and indicates that bears are using different habitats at lower elevations. This is because the whitebark pine nut, an important food for grizzlies in vulnerable times of late autumn and early spring, has been in decimated by climate change. The temporal range of the parasitic mountain pine beetle has allowed them to feast on the trees later into the fall and earlier every spring, as a result this nutritious, fat-laden resource is less available, causing grizzlies to move down the mountainside in search of increased sustenance. In short, range expansion is a consequence of climate change, not increased grizzly numbers.

In addition, the Yellowstone grizzly population is suffering from a lack of genetic diversity. Large mammals and especially carnivores need to disperse over long ranges to maintain genetic viability. As the Yellowstone grizzly is cut off from other populations to the north and west, there is a dangerous lack of genetic diversity in the Yellowstone grizzly population, another argument to keep the bears protected.

Furthermore, the USFWS is using the ESA distinct population segment language against the original intent of the ESA. The distinct population segment provision was added to the act so that population segments of non-threatened species could get protection where they needed it, but the agency is using this language in the opposite way: to divide up segments that are already vulnerable to justify removing them from the endangered species list.

Costello, C. M. et al. 2014. “Influence of Whitebark Pine Decline on Fall Habitat Use and Movements of Grizzly Bears in the Greater Yellowstone Ecosystem”. Ecology and Evolution 4: 2004-2018.

Craig, C.R. and Waits, L.P. 2003. “The History of Effective Population Size and Genetic Diversity in Yellowstone Grizzly: Implications for Conservation”. Proceedings of the National Academy of Scientists 100 (7): 4338.

Mattson, D.J. and Merrill T. 2002. “Extirpations of Grizzly Bears in the Contiguous United States, 1850-200”. Conservation Biology 16 (4): 1123-1136.

Merrill, T and Mattson D.J. 2003. “The Extent and Location of Habitat Biophysically Suitable for Grizzly Bears in the Yellowstone Region”. Ursus 14:  171-187