Aspen have the greatest geographic range of any North American tree species. They are popular and esthetically pleasing because of their white bark, quaking leaves, and bright yellow fall color. They are an important source of fiber for wood products and help provide protection for watersheds and riparian areas. Aspen are also a key ecosystem component for wildlife and contribute to biodiversity. Ungulates such as elk and cattle browse on aspen sprouts and may be suppressing regeneration.
Elk also strip bark from larger trees, which gives pathogens a way in.
Suppression of wildfires may let conifers encroach and shade out aspen stands. Despite the extent of the problems facing aspen, there has been almost no federal funding for aspen research since the mid-1980s. Funding has come from a cooperative consisting of the National Park Service and the University of Wyoming. The OSU Research Council has provided additional funding, with which Ripple and Larsen have collected more data around Yellowstone, both within the park and in the neighboring Gallatin and Shoshone national forests. In addition, they recently conducted a field research day in Oregon's Umatilla National Forest, consulting with area foresters and wildlife biologists on the status of aspen in the Blue Mountains.