Viewpoint: ungulate herbivory, willows, and political ecology in Yellowstone.

Abstract

Contentions that willows (Salix spp.) on Yellowstone National Park's northern range have declined because of climatic change, fire suppression, reduced chemical defenses, or other natural factors are not supported by available data. Instead, willows have declined due to repeated browsing by an unnaturally large elk population. By established standards Yellowstone contains some of the worst overgrazed willow communities in the entire West, but that was not true in earlier times. Prior to park establishment, predation by Native Americans kept elk and other ungulate numbers low which, in turn, prevented herbivores from impacting Yellowstone's plant communities, as those animals do today. Finally, the condition of willows in the park is also a test of Yellowstone's "natural regulation" program, and that paradigm must also be rejected.