The eradication of the wolf from the lower 48 United States was a tragedy. But there was one benefit that came from it – it taught us why we can never let it happen again.
As natural predators, wolves play a critical role of managing ungulate species, a role that cannot be replaced and that has dire consequences when not fulfilled.
By observing the ecosystem with wolves, without wolves, and then with wolves again, we were able to study the cascading effects of a keystone species and learned about a fascinating concept called trophic cascades.
In this way, the Yellowstone ecosystem gave us the perfect opportunity to showcase the essential role of a keystone predator like the gray wolf.
A Keystone Species
Wolves are often called a keystone species, meaning that their impact on the ecosystem is disproportionately large compared to their population size.
Keystone species have effects that cause a domino effect down the food chain, affecting many other species and organisms.
In the case of wolves, their predation on herbivores like elk and deer is not just about limiting prey numbers—it’s about regulating the behaviors of other species and the long chain of events that follow.
By making ungulate species more cautious, they prevent overgrazing and foster the growth of diverse plant and animal life that would struggle to survive in a wolf-free ecosystem.
By noticing these effects of the Yellowstone Wolf Reintroduction, we learned about trophic cascades.
Trophic Cascades: The Yellowstone Case Study
When wolves were eradicated in the 1900s, Yellowstone’s elk population exploded, leading to overgrazing in many parts of the park.
This was especially harmful along rivers, where the lack of vegetation created serious erosion.
Willow and aspen saplings, crucial for both soil stability and as habitat for other wildlife, were stripped down by the large elk population.
When wolves were reintroduced, things began to change.
Elk learned to avoid open spaces, allowing those overgrazed areas to regenerate, strengthening riverbanks and creating habitats for a variety of species.
The growth of riparian vegetation brought back beavers, another keystone species, whose dam-building activities created even more diverse aquatic habitats that benefit fish, amphibians, and other wildlife.
Wolves reduced the coyote population, another species that had become overpopulated in their absence, allowing various small mammal species to flourish.
Even scavenger species, like bears, ravens, and eagles, benefited from scraps at wolf kills, which provided a reliable food source.
Because of these changes and various others throughout the ecosystem, the entire landscape began to shift toward a healthier, more balanced state.
The return of the wolf in Yellowstone has shown that natural systems function best when they have all their parts, particularly top predators.
The trophic cascade initiated by wolf reintroduction stands as a reminder that nature thrives on balance—a balance that wolves help maintain.