If you’re lucky, you can spot a gray wolf in Yellowstone National Park. But a century ago, you’d have been hard pressed to find any there. Poisonings and unregulated hunting obliterated nearly all of these majestic canines from Canada to Mexico, their original home range.

Then the rewilding began.

Since their reintroduction to Yellowstone and Idaho in the 1990s, gray wolves have done so well that they’re reclaiming other parts of the northern Rockies.

In the places where they returned, wolves tidied up explosive deer and elk populations, which had eaten valleys barren. That helped bring back trees and shrubs. Birds and beavers, as well as the animals that live in dams, also returned. The wolves ate coyotes, freeing up their prey for others. Bears and raptors came back for carrion. With more trees controlling erosion, the flows of some rivers were less chaotic, forming pools that became new habitats.

“We’re just uncovering these effects of large carnivores at the same time their populations are declining and are at risk,” said William Ripple, an ecologist at Oregon State University. He’s found that if you rewild some carnivores, or return them back to lost ranges, a cascade of ecological bounty may follow.