The Healing Impact of Yellowstone’s Wolves May Be Overrated

They probably didn’t change the path of the river.

Pictured: not actually good at civil engineering projects.Photo byThomas Bonometti on Unsplash

In 1995, in a huge win for ecologists and conservationists, wild wolves were re-introduced back into Yellowstone National Park. They’d been absent for nearly 100 years, having been exterminated in the early 1900s through a combination of habitat loss and hunting programs.

In the last thirty years, the wolves have thrived. They’ve helped control the populations of other animals in the park in what is called a trophic cascade.

A viral video from 10 years ago even put forward that the reintroduction of wolves changed the course of the Yellowstone River.

But did they really? Or was this an over-generalized and oversimplified conclusion?

The story may not be as clear-cut as a four-minute video claims.

The avalanche rushing through the food chain?

Wolves are apex predators; like humans, they occupy a spot at the top of a multi-stage food chain. Their primary prey are the herds of elk that live in Yellowstone.

But this isn’t simply a matter of wolves cutting down the overgrown population of elk. The elk population has actually increased since the late 1960s.

Instead, the reintroduction of the wolves helped to change the elk behavior.

With wolves as a threat, the elk cannot stay in one place as long and cannot graze as heavily. They need to stay on the move, to keep away from the wolves. This means that the elk cannot graze as heavily on specific areas of the park.

Stands of willow trees grow along the banks of the Yellowstone river. These were previously heavily grazed by the elk, but now that the elk are more frequently on the move, the willow clumps have regrown, stretching further out along the edges of the river.

These trees, in turn, became food for another animal: beavers. Beavers moved in on the new willow trees, grazing them — and turning them into dams that slow the river and provide habitat for other creatures.

This is the true impact of a trophic cascade, where a change at one level of the food chain (presence or absence of wolves) has far-reaching effects on the rest of the chain.

But did the change really “heal” the entire ecosystem?

Elk aren’t the only large grazers

One of the big holes in this beautiful story of “healing nature” comes when we look at other potential causes. Yes, wolves hunted and put pressure on the elk populations after they were reintroduced — but from 1995 through 2003, the biggest threat to the elk were human hunters, not the wolves.

Another wrinkle: wolves weren’t the only animals re-introduced to the park by the U.S. Forest Service. They also released 129 beavers between 1986 and 1999.

Meanwhile, although the willows (and aspen trees, which also grow in stands along the river) are growing back in some places, other areas on the river remain bare. This has been exacerbated by another large grazing species: the bison.

Pictured: problematic.Photo bymana5280 on Unsplash

Elk populations have declined, but bison populations have risen, approaching 5,000 animals (far more than the 124 wolves as of winter 2023). Bison also graze on and destroy aspen saplings, and they’re not as vulnerable to the wolves as the elk; it’s a lot harder for wolves to bring down a bison.

Due in large part to the bison moving in to graze the areas previously claimed by elk, a number of willow and aspen stands haven’t regrown. This is driven further by our warming climate, which makes the summers hotter and drier, further reducing growth along the rivers.

The impact of the wolves, and the “healing” of the park, may not be nearly as significant and complete as TikTok videos suggest.

Yellowstone is especially vulnerable to global warming

Reduced growth of trees along the Yellowstone river isn’t the only danger facing the park.

In 2022, extensive flash floods took out roads and forced the park to close for two months. But the other extreme — wildfires — are an increasing threat as well. The park region is, on average, warmer than it has been in the last 20,000 years. The snow lines are creeping higher, retreating as the rest of the park warms.

The warming, changing climate, along with reductions in water availability, will likely have larger impacts on the forests of Yellowstone than the reintroduction of wolves or the release of beavers. Trees are predicted to grow patchier and less dense, stressed by the combination of heat and dryness.

Because Yellowstone is at a high elevation, at an average of 8,000 feet above sea level, it’s more strongly impacted by global warming. The higher elevation means a thinner atmosphere, which means more pronounced heat effects.

Soon, the changing climate may push migrating herd animals like elk and bison — and the wolves that prey on them — out of Yellowstone completely, as they seek areas that match their traditional habitat.

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The idea of “healing an environment” by restoring its natural balance, including predators, is a nice one. But these restoration efforts aren’t going to overcome systemic impacts of global climate change.

The re-introduction of wolves into Yellowstone does appear to have provided some benefits that echo up and down the food chain. But the best way to support the long-term health of national parks is to fight against climate change, and vote for candidates willing to recognize the dangers of a warming world.

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