“Wolves are to Yellowstone what water is to the Everglades,” said Doug Smith, the former director of the Yellowstone Wolf Recovery Project.
That sentiment is especially evident in a recent study highlighting the predators’ slow yet steady role in bringing an ecosystem back into balance - all the way down the food chain, from elk populations to plants.
In January 1995, eight gray wolves were brought by truck from Canada to Yellowstone. They were the first to set foot in the park in about seven decades, and by the following year, their number had more than tripled. And have continued to grow, all the while reshaping and rebalancing the landscape.
In a new study, researchers evaluated a phenomenon referred to as a “trophic cascade,” or the indirect effects of predators on a food web’s lower levels. They found that willow tree volume increased by 1,500 percent over the span of 20 years, spurred by the reintroduction of wolves to Yellowstone in 1995. As willow is a common food source for elk and elk are a primary food source for wolves, more wolves means fewer elk and more willow.
“Our findings emphasize the power of predators as ecosystem architects,” says lead study author William Ripple, noting the importance of abundant willow as a vital food resource and habitat for birds and other animal species.
“The restoration of wolves and other large predators has transformed parts of Yellowstone, benefiting not only willows but other woody species such as aspen, alder, and berry-producing shrubs. It’s a compelling reminder of how predators, prey, and plants are interconnected in nature,” he added.
The study concludes: "This knowledge can inform future conservation efforts and adaptive management strategies, especially in ecosystems undergoing restoration, where accurate assessment of trophic cascade dynamics is essential for evaluating recovery progress and biodiversity outcomes."