A 20-year study by Colorado State University (CSU) reveals that reintroducing apex predators into an ecosystem doesn’t immediately reverse changes caused by their absence. This research, funded by the National Science Foundation, contradicts the common belief that reintroducing wolves to Yellowstone National Park restored its degraded ecosystem. The study examined the impact of three apex predators – wolves, cougars, and grizzly bears – on Yellowstone. Their absence for nearly a century significantly altered the park’s food web and landscape.
The study discovered that without these predators, Yellowstone’s northern range transformed from willow and aspen stands along small streams with beaver activity to grasslands due to elk overgrazing. These changes created a new ecological state that didn’t revert to its previous state even after the predators were reintroduced. The study, led by Tom Hobbs and David Cooper, is the longest of its kind and supports the idea that ecosystem degradation may not be reversible even when harmful factors are removed.