The extirpation and subsequent reintroduction of the gray wolf to Yellowstone National Park has created a rare opportunity to understand how predators can change ecosystems. Wolves were extirpated from Yellowstone during the early twentieth century. Their loss led to a dramatic increase in the number of elk, which is believed to have subsequently caused substantial changes in vegetation along the park?s network of streams. Wolves were reintroduced to Yellowstone in 1995. It was hypothesized that the reintroduction of wolves would cause a rapid restoration of riparian communities due to their effects on elk numbers and behavior. A 10-year experiment manipulating herbivory and water availability has thus far found little support for the idea that wolves have changed the ecosystem by releasing plants from herbivory by elk.
The abundance of elk in the Park has only recently declined to levels that were typical prior to the extirpation of wolves. Thus, it is plausible that there has not been sufficient time for vegetation to respond to reduced elk density resulting from wolf reintroduction. The 10-year experiment will be continued to better understand how climate, hydrology, and herbivory may control riparian ecosystems. The manipulative experiment will be supplemented with landscape-scale observations to provide a larger scale context in which to understand how wolves, elk, bison and weather interact to determine the state of the ecosystem.
The demonstrated interest of citizens in the unfolding story of wolves in Yellowstone assures that research findings will be communicated in the popular media. In addition, the research team will collaborate with Yellowstone National Park staff to offer citizen education to three million visitors to the park through interpretive programs. Additional broader impacts will result from graduate and undergraduate student training, and because data from this long term study will be made easily available to the scientific community.
