A new study supports others in recent years that refute popular claims by anti-hunting and animal rights groups that the reintroduction of wolves into the Greater Yellowstone Ecosystem (GYE) spawned ecological change for the better.

The trophic cascade theory, popularized in 2012, maintains a change at the top of the food chain triggered beneficial impacts that trickled down to the bottom. The new research disputes the method of those 2012 findings by examining the theory that asserts the presence of wolves caused a 1,500 percent increase in the height of willows leading to reshaped rivers and improved landscapes.

“Our re-analysis shows their conclusion is invalid because it relies on circular reasoning and violations of basic modeling assumptions," Daniel MacNulty, study author and Utah State University ecologist, told Science Daily. “Because height was used both to compute and to predict volume, the relationship is circular -- mathematically guaranteed to look strong even if no biological change occurred.”

According to Science Daily, the statistical method used by the original researchers portrayed the wolf-willow growth connection as a strong one, even if that growth did not change. Other methodology concerns included sampling bias, assumptions and apple-versus-orange comparisons to studies outside of the GYE.

Earlier studies mimic the findings of this most recent research and dispelled trophic cascade. October 2024 research analyzing 21 years of data showed the primary driver of decreased elk browsing pressure and increased aspen tree regeneration was a reduction in elk population density caused by predation from multiple predators – wolves, bears, mountain lions and hunters.

A January 2024 study that spanned more than two decades examined the effects of three GYE apex predators – all carnivores at the top of the food chain not preyed on by other animals in that same landscape. Depleted populations of mountain lions and grizzly bears naturally recovered about the same time wolves were reintroduced to the park in 1995. The absence of these predators for nearly a century transformed the food web and landscape. The designed experiment adds to evidence supporting the theory that degradation of ecosystems may not be reversed when harmful stressors are mitigated. 

The lead researcher of a 2021 study described how the 2012 trophic cascade research measured only the five tallest young aspen in a given stand of trees which led to an “overestimated regeneration of overstory aspen…compared to random sampling because it favored plants taller than the preferred browsing height of elk and overlooked non-regenerating aspen stands.” The scientific team further highlighted the critical importance of basic sampling principles for achieving an accurate understanding of trophic cascades.

In 2019, scientists from three universities in two countries said more testing was needed about this “assumption of reciprocity.” And in 2010, another team of researchers determined young aspen in Yellowstone were not recovering despite the presence of wolves.

Referring to a 2014 viral video promoted by anti-hunting and animal rights groups that proclaimed wolf-related trophic cascade as fact, MacNulty told AccuWeather.com this in 2018: “It’s a really romantic story. It’s a story about a world that doesn’t really exist.”

About Hunt 2 Conserve

Hunt 2 Conserve is a 501(c)4 nonprofit organization affiliated with the Rocky Mountain Elk Foundation. Its mission is to advance a legacy of hunting and conservation by educating, activating and developing stewards and defenders of these fundamentally American ideals. For more information, go to hunt2conserve.org.

(Photo credit: Rocky Mountain Elk Foundation)