A trophic cascade is an ecological phenomenon that occurs when changes in the population of one species affect multiple levels of the food chain. For example, if a predator like the wolf is removed from an ecosystem, the population of its prey, such as deer, may increase significantly. This overpopulation can lead to overgrazing, which negatively impacts plant life and alters the entire habitat. Conversely, reintroducing a predator can help restore balance. When wolves were reintroduced to Yellowstone National Park, they helped control the deer population, allowing vegetation to recover. This, in turn, benefited other species and improved overall ecosystem health.