Yellowstone's northern range: complexity & change in a wildland ecosystem

National Park Service, Yellowstone National Park

The condition of the winter range of the northern Yellowstone elk herd (referred to here as the northern range) of Yellowstone National Park has been of concern to the public, managers, and scientists for more than 70 years. Before 1970, almost all observers regarded the range as overgrazed due to an overpopulation of elk. Other problems thought to have been caused by high elk numbers included declines in woody vegetation, especially willow and aspen, declines in white-tailed deer and beaver, and increased erosion. These concerns led to increasingly aggressive attempts to control elk herd size, which peaked in the 1960s when thousands of elk were slaughtered. The agency's control actions resulted in a monumental public outrcry and U.S. Senate hearings that led to the termination of elk control in the park. Because of changing attitudes about natural systems in the scientific community and growing uncertainty over how ecological processes worked in Yellowstone National Park, National Park Service (NPS) managers and biologist decided to test the common assumption that the elk were inevitably inclined to overpopulate the range and, alternatively, to determine if the elk herd might be "naturally" regulated, or regulated by its environment. Natural regulation of animal populations was an established topic in ecology by the 1950s. In the 1960s and 1970s, by applying prevailing ecological theories relating to natural regulation, NPS scientists provided substantial evidence that traditional views of the ranged as overgrazed were either erroneous or based on incomplete information.