Restoring Riparian Ecosystems with Large Predators: the Yellowstone Experience
Location
USU Eccles Conference Center
Abstract
Large predators can help shape the structure and functioning of terrestrial ecosystems. While various studies in national parks scattered across the western United States and Canada have shown the loss of large predators (e.g., wolves, cougar) allowed native ungulates (e.g., elk, mule deer) to greatly alter the structure and functioning of ecosystems via increased herbivory, studies of trophic effects of reintroduced/recolonized large predators have been relatively rare, with Yellowstone National Park being a major exception. The reintroduction of wolves into Yellowstone National Park in 1995-97, after a 70 year absence, allowed for studies of trophic cascades of a restored large predator guild upon elk and woody species such as aspen, cottonwoods, willows, and berry- producing shrubs. Overall, these studies indicate that the reintroduction of wolves triggered a trophic cascade, in conjunction with bottom-up forces, with increasing recruitment (i.e., growth of woody plants into tall shrubs or trees) of browse species in riparian areas. This situation represent a fundamental change in plant community dynamics in comparison to previous decades of browsing suppression--when wolves were absent. Although wolf reintroduction has resulted in substantial initial effects to both plants and animals, the Yellowstone ecosystem still appears to be in the early stages of ecosystem recovery. In other areas of western North America where large carnivores have been previously extirpated or displaced, their recovery may be necessary for assisting in the ecological restoration of large herbivore altered ecosystems.
Restoring Riparian Ecosystems with Large Predators: the Yellowstone Experience
USU Eccles Conference Center
Large predators can help shape the structure and functioning of terrestrial ecosystems. While various studies in national parks scattered across the western United States and Canada have shown the loss of large predators (e.g., wolves, cougar) allowed native ungulates (e.g., elk, mule deer) to greatly alter the structure and functioning of ecosystems via increased herbivory, studies of trophic effects of reintroduced/recolonized large predators have been relatively rare, with Yellowstone National Park being a major exception. The reintroduction of wolves into Yellowstone National Park in 1995-97, after a 70 year absence, allowed for studies of trophic cascades of a restored large predator guild upon elk and woody species such as aspen, cottonwoods, willows, and berry- producing shrubs. Overall, these studies indicate that the reintroduction of wolves triggered a trophic cascade, in conjunction with bottom-up forces, with increasing recruitment (i.e., growth of woody plants into tall shrubs or trees) of browse species in riparian areas. This situation represent a fundamental change in plant community dynamics in comparison to previous decades of browsing suppression--when wolves were absent. Although wolf reintroduction has resulted in substantial initial effects to both plants and animals, the Yellowstone ecosystem still appears to be in the early stages of ecosystem recovery. In other areas of western North America where large carnivores have been previously extirpated or displaced, their recovery may be necessary for assisting in the ecological restoration of large herbivore altered ecosystems.
Comments
Robert Beschta is professor emeritus in the department of Forest Ecosystems and Society at Oregon State University. Much of his research has been directed at trying to understand the effects of alternative land uses upon riparian plant communities, hydrologic processes, and stream systems. Over the last 15 years, he has been involved in studies trying to assess apex predator effects, via their presence or absence, on plant communities and riparian ecosystems. These efforts have generally involved retrospective assessments of ecosystem trends following the displacement/extirpation of an apex predator, as well as ecosystem changes underway in areas where the missing predator has returned.