The return of wolves to Yellowstone has triggered sweeping changes to the ecosystem, — Forbes
In 1995, gray wolves were reintroduced to Yellowstone National Park, where they had been absent for nearly 70 years after their disappearance in the 1920s.
Biologist Scott Travers wrote about this in an article for Forbes.
This decision led to large-scale and long-lasting changes in the region’s ecosystem.
Before the wolves were reintroduced, moose dominated the park, actively feeding on young shoots of willow, aspen, and poplar, especially in valleys and riparian zones. This led to vegetation degradation, weakened riverbanks, and increased erosion, causing watercourses to lose their natural complexity and stability.
After the return of the predators, a trophic cascade effect began to take place, where changes at the top of the food chain affect the entire ecosystem. Wolves not only reduced the moose population but also altered their behavior: the animals began to avoid certain areas due to the risk of attack. This phenomenon is also described as the “ecology of fear.”
As a result, young trees began to actively regenerate, especially along rivers and in valleys. This contributed to the restoration of riparian vegetation and the stabilization of riverbanks, which reduced erosion.
The restoration of willow thickets has had a positive impact on beaver populations, as these trees are their primary food source and building material. As the number of beavers increased, new dams began to form, creating wetlands, raising groundwater levels, and supporting biodiversity.
The condition of aquatic ecosystems has also improved: erosion has decreased, the water has become cleaner, and the shading of streams has helped regulate its temperature, which is important for fish and invertebrates.
Wolves have also influenced other species, as the remains of their prey have become an additional food source for scavengers—crows, eagles, foxes, bears, and insects—strengthening ecological connections in the region.
Thus, the return of wolves to Yellowstone has become an example of how the reintroduction of a single predator species can trigger large-scale changes throughout the entire natural system—from animal behavior to river structure and landscape.
As a reminder, Finland recorded a record number of reindeer deaths last year—over 2,100 animals fell victim to wolf attacks. Local reindeer herders believe that the sharp increase in the predator population is linked to Russia’s war against Ukraine.
