This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: You might be among the 46 million people who've seen a video showing how wolves changed Yellowstone, or you may have heard another version of the story. Yellowstone, which covers nearly 3,500 square miles (9,100 square kilometers) of the western United States, was the world's first national park.
Its pioneering reintroduction of wolves, which began in 1995, set a worldwide precedent for conservation. The first half of the story is well established. Wolves were eradicated from Yellowstone in the 1920s.
With the wolves gone, populations of elk (a large species of deer) grew too large. Elk overgrazed the park's riverbanks, turning groves of willow and aspen and beaver ponds into bare grasslands. This process was swiftly reversed, or so the story goes, when wolves were reintroduced.
Not only did wolves kill elk, keeping their numbers in check, but they also scared them away from the valleys, giving trees a chance to regrow. A range of beneficial effects followed: Beavers moved back and rebuilt their dams, and the regrown shrubs attracted more bears, who further helped keep elk in check. It's a neat and captivating story, widely cited as evidence that wolves can restore ecosystems and reforest the land.
Unfortunately, reality is much more complicated. Wolves did not, by and large, restore Yellowstone. Understanding the science behind this can teach us a lot about how ecosystems work.
Even more interestingly, reflecting on why so many people are keen to believe the story can tell us a lot about ourselves and our relationship with nature. The story originated with scientific studies in the early 2000s, built on a theory known as "trophic cascades": the idea that changes at the top of the food chain can cascade down to its very bottom. For example, wolf eats elk eats willow: More wolves mean fewer elk, which means more and taller willows.
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