Landscape Configurations in Yellowstone National Park: An Alternative State Stabilized by Herbivory?

Colorado State University, Fort Collins CO

Investigators

Abstract

Human actions can cause unintended effects on nature. Often, these actions can cause natural systems to change abruptly from their historic condition to new conditions that may be undesirable. The removal of wolves from Yellowstone National Park appears to be an action that has caused unanticipated harm to the ecosystems of the park, in particular, the loss of trees and shrubs from stream corridors. These plants enhance water quality, stabilize stream banks, and provide habitat for many species of wildlife. It appears that elimination of wolves allowed elk populations to reach levels where their browsing prevented willow reproduction and increased willow mortality. The absence of beaver with the demise of much of the willow habitat, resulted in fundamental changes in streams, rendering them less suitable as habitat for willows. This study will determine whether the re-introduction of wolves to Yellowstone National Park has allowed the northern range to recover to its historic condition with abundant willow communities and vigorous populations of beaver. Several approaches will be used including assessments of aerial photographs and quantitative modeling of the system. A National Academy of Sciences report identified understanding the effects of availability of water and browsing by elk on communities of willows as a problem of urgent importance for policy and management in Yellowstone National Park. The proposed work will address a problem of fundamental scientific value in a location where science can be immediately applied. The work provides a valuable opportunity to communicate science to citizens, managers and policy makers.