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How Wolves Saved the Foxes, Mice and Rivers of Yellowstone National Park

A wolf standing in a river next its prey in Yellowstone National Park.

A wolf standing in a river next to its prey in Yellowstone National Park.

CrackerClips Stock Media/Shutterstock

Editor's Update, December 16, 2015: Wolves in Wyoming, Michigan, Minnesota and Wisconsin will retain their federal protections after a contentious policy “rider” that would have stripped them of Endangered Species Act protections was excluded from the final omnibus government spending bill released on December 15, 2015. Read the press release here.

The land of Old Faithful wasn’t always so lush. Two decades ago, Yellowstone National Park was the victim of defoliation, erosion and an unbalanced ecosystem. But in 1995, everything changed.

That was the year wolves were reintroduced to the park. Before then, government predator control programs had all but eliminated the gray wolf from America’s lower 48 states. Consequently, deer and elk populations increased substantially, resulting in overgrazing, particularly of willows and other vegetation important to soil and riverbank structure, leaving the landscape vulnerable to erosion. In the absence of wolves, the entire ecosystem of the park suffered.

A film, which has garnered more than 18 million views on YouTube, gives a captivating explanation of Yellowstone’s turnaround. British writer George Monbiot lends his voice to this short documentary, and his zeal is infectious as he describes how wolves reinvigorated the park. “We all know that wolves kill many animals, but perhaps we’re slightly less aware that they give life to many others,” he says in the film. So much of our knowledge of these creatures focuses on their potential threat to humans, rather than their biological importance. 

As a top predator, wolves are one of Yellowstone’s linchpins, holding together the delicate balance of predator and prey. They even impact the physical landscapes around them. Their removal in the early 20th century disrupted food webs and set off something called a “trophic cascade,” in which the wolves’ natural prey (in this case, elk) multiplied, all the while consuming increasing amounts of foliage. The phenomenon occurred again in reverse when the wolves were reintroduced and the natural balance was restored.

When wolves were brought back to the park, they not only killed elk but also changed their prey’s behavior patterns. The herbivores started to avoid areas like valleys and gorges where they could be easily hunted by predators. As a result, those areas began to regenerate, and species such as birds, beavers, mice and bears returned. Plant life once again thrived along the riverbanks and erosion decreased significantly. The stabilization of the riverbanks actually made the rivers and streams change course. With the reintroduction of just a small population of wolves, the landscape of the whole park transformed.

Earthjustice has been fighting for more than 20 years to protect wolves in the Northern Rockies ecosystem. The current fight is centered in Washington D.C. where Congress is considering legislation that would remove Endangered Species Act protections for wolves in multiple states. This video demonstrates the importance of combating such legislation. In a recent nation-wide poll, 90 percent of Americans said they support the Endangered Species Act. Efforts to boost wolf populations are essential, not just for Canis lupus, but for the ecosystems it supports.

About this series

2015 marks the 20th anniversary of the reintroduction of gray wolves to the northern Rockies, and since that time wolves have been under nearly constant threat of losing their protections. The Weekly Howl provides insights and education about the gray wolf and updates on the status of its protections while celebrating the iconic species as a vital part of a functioning, healthy ecosystem. Posts will appear every Wednesday starting June 17 and running through the summer.

Don’t miss last week’s post: “Telling Wolves to "Shoo!" An Interview With Real 'Wild' Woman Meredith Taylor.”

About the Earthjustice Blog

unEARTHED is a forum for the voices and stories of the people behind Earthjustice's work. The views and opinions expressed in this blog do not necessarily represent the opinion or position of Earthjustice or its board, clients, or funders. Learn more about Earthjustice.