Wolves have been back in Yellowstone Park for 25 years

Yellowstone wolves keeping the elk population in check.
(Getty Images photo by Jeff Vanuga)

Twenty-five years ago in January, U.S. and Canadian agencies reintroduced wolves to Yellowstone National Park in an effort to correct an ecosystem "dangerously out of whack, owing to the extirpation of its top predator," Cassidy Randall reports for The Guardian.

It was the first deliberate attempt to return a top carnivore to a large ecosystem. "Now scientists are celebrating the gray wolves’ successful return from the brink of extinction as one of the greatest rewilding stories the world has ever seen," Randall reports.

Wolves were once common in vast swaths of North America, but humans killed them indiscriminately, believing them to be a danger, though wolves rarely attack humans and kill about one-fourth of 1 percent of available wildlife. The last wolves were killed in Yellowstone in 1926 as part of a policy to eliminate predators, Randall reports.

The Endangered Species Act obliges the U.S. Fish and Wildlife Service to protect endangered and threatened species and create a plan for increasing their numbers. Farmers and ranchers opposed return of wolves to Yellowstone so strongly that they weren't reintroduced to the park until 1995, more than 20 years after the ESA was enacted, Randall reports.

Yellowstone National Park map

Yellowstone needed the predators badly. "In the 70 years of the wolves’ absence, the entire Yellowstone ecosystem had fallen out of balance. Coyotes ran rampant, and the elk population exploded, overgrazing willows and aspens," Randall notes. "Without those trees, songbirds began to decline, beavers could no longer build their dams and riverbanks started to erode. Without beaver dams and the shade from trees and other plants, water temperatures were too high for cold-water fish."

Though scientists knew wolves would help the ecosystem, they were surprised by how quickly it happened. "The elk and deer populations started responding immediately. Within about 10 years, willows rebounded. In 20, the aspen began flourishing. Riverbanks stabilized. Songbirds returned as did beavers, eagles, foxes and badgers," Randall reports.

The wolves have helped bring in more revenue to Yellowstone, too. The wolf reintroduction cost about $30 million, but wolf ecotourism brings in $35 million every year, since Yellowstone is one of the best places in the world for tourists to observe wild wolves, Randall reports.

The Yellowstone wolves have spread outward, repopulating areas as far away as Colorado, northern California, and eastern Oregon and Washington, Randall reports.