“A 20-year study on the effects of reintroducing wolves into Yellowstone National Park found that removing the apex predators has caused far more damage than expected to the park’s ecosystem.”
What happened?
Colorado State University researchers launched the study in 2001 to determine if bringing gray wolves, grizzly bears, and cougars back to Yellowstone’s northern range would help its food web and ecosystem recover, according to the university’s summary of the study.
The nonprofit Yellowstone Forever explained that these large carnivores had been eradicated from the park by the 1920s in an attempt by the U.S. government to control the predators’ populations.
However, without predators to keep the ecosystem balanced, elk numbers skyrocketed to unsustainable levels, which led to the decimation of willow and aspen trees along small streams. In turn, beavers that used willows as a food and shelter source left the area, which meant the trees’ root systems no longer benefited from the flooding caused by beaver dams.
Scientists thought the reintroduction of wolves to the park in 1995 would allow the animals and plants to recover from the cascading effects of losing apex predators, but they found it wasn’t that simple, as the summary stated.
While cougars and grizzlies have made a comeback, bison herds have replaced many elk. Since they share the elks’ food sources, willow and aspen trees remain threatened.
“When you disturb ecosystems by changing the makeup of a food web, it can lead to lasting changes that are not quickly fixed,” Tom Hobbs, lead author and professor emeritus with the Department of Ecosystem Science and Sustainability and the Natural Resource Ecology Laboratory, said in the report.
Why is this concerning?
Unfortunately, what’s happening in Yellowstone is just a glimpse into what happens when ecosystems get disrupted globally.
Eliminating crucial Yellowstone species harms water and food sources for animals and impacts the entire food web. While the ecosystems can recover, as the researchers noted, it can take decades for them to be fully restored.
“The conservation message is don’t lose them in the first place,” Hobbs said. “Keep the food web intact, because there’s not a quick fix for losing top predators from ecosystems.”