When 14 grey wolves were released into Yellowstone in 1995, no one fully predicted what would follow. Elk changed how they moved. Riverbanks recovered. Even the rivers began to change course — a single reintroduction triggered an entire ecosystem's rebirth.
The Absence of Wolves
When wolves were eradicated from Yellowstone in the 1920s, few imagined the ecological cascade that would follow. Without predators, elk grazed river banks bare, destabilising soils and destroying vegetation.
Fourteen Wolves Change Everything
In 1995, biologists introduced 14 grey wolves from Canada into Yellowstone. The effect was extraordinary. Elk began avoiding open valleys. Riverbanks revegetated. Willows and aspens returned. Beavers followed, damming streams and creating wetland habitats for fish, birds, and otters.
>> "Wolves didn't just kill elk — they changed how elk moved through the landscape, and the rivers themselves began to change course."
The rivers themselves began to change course — a phenomenon called a trophic cascade. Today Yellowstone hosts over 100 wolves, and the ecosystem is measurably healthier than it was in decades.