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Abstract
We investigated how large carnivores, herbivores, and plants in ecosystems with and without wolves (Canis lupus) may be linked to the maintenance of native species biodiversity through trophic cascades. The extirpation of wolves in the mid-1920s from Yellowstone National Park and their reintroduction in 1995 provided the basis for examining the cascading effects of carnivore/herbivore interactions on woody browse species, as well as additional ecological responses involving riparian functions, beaver (Castor Canadensis) populations, and general food web support. Results indicate that predation risk (or the lack thereof) may have profound effects on the structure of ecosystems and is an important constituent of maintaining native biodiversity. Our conclusions are based on theory involving trophic cascades, predation risk, and optimal foraging, as well as literature from empirical research and recent studies in Yellowstone National Park. Additional research is needed to understand how lethal effects interact with nonlethal effects (predation risk) to structure ecosystems.