The Wolves of Yellowstone Gray wolves were reintroduced into Yellowstone National Park in 1995, resulting in a trophic cascade through the entire ecosystem. After the wolves were driven extinct in the region nearly 100 years ago, scientists began to fully understand their role in the food web as a keystone species. TRANSCRIPT: In 1995, something really exciting happened in the nation’s first national park, Yellowstone. 41 wild wolves are reintroduced here by scientists. After 100 years of being hunted, wolves could once again call this place home. The wolves thrived, but something else very surprising happened. Their return had a spectacular effect on the landscape, an effect that spread wider than anyone thought possible. So how did this all happen? In the past, wolves were seen as a risk to people and livestock, and they were exterminated from the Yellowstone area in the 1920s. The elk’s main predator was gone, and their population more than doubled. Elk are both grazers and browsers, so they eat grass, shrubs, and trees. They overgraze the entire park, upsetting the natural balance of the ecosystem. Mammals like mice and rabbits could not use the plants to hide from predators, and their populations fell dramatically. Grizzly bears suffered as the elk munch away their berry supply, which they badly need to build up fat before hibernating. Pollinators like bees and hummingbirds had fewer flowers to feed on, songbirds less trees to nest in. Perhaps the elk’s most devastating impact was how they affected the park’s…