Yellowstone: Wolves, Willows & Trophic Cascades

Wolves, willows...and what? What is a “trophic cascade”? What role do they play in the health of the Yellowstone ecosystem—and why are scientists arguing about it? The term may sound technical, but you’re sure to find this ecological phenomenon riveting, especially as it’s interpreted by naturalist guide Aaron Bott, who lives and works in the Greater Yellowstone Ecosystem. A trophic cascade is triggered by adding or removing a top predator from an ecosystem, which then has a trickle-down effect on the entire food web. It effects reciprocal changes in populations of predator and prey that result in dramatic changes in the entire structure of an ecosystem. Advocates for wolves reintroduced to Yellowstone may contend, for example, that their presence has helped restore greater balance and health to the ecosystem—evidenced in increasing beaver populations through reducing too-dense elk herds and thus allowing willows to flourish which beavers rely on for winter survival. But, as Aaron will explain, it’s not that simple. Since wolves were returned to Yellowstone National Park in 1995, scientific debate has simmered regarding the actual impacts this apex predator has had on the landscape. Join Aaron to learn what scientists know for sure, and what is still uncertain. Contrary to what you may have heard, it's a pretty complicated—and intriguing—story.


Originally presented March 26, 2021

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