There’s A New Debate Over Wolves’ Impact On Yellowstone

Ahhh, science, it's always evolving. I read a Science Daily report about the wolves of the Yellowstone Ecosystem. For nearly 70 years, they were gone from Yellowstone, but then later reintroduced in 1995-96, and now about 500 wolves are there. A lot of time is spent discussing the wolves, and depending on who you ask, they're either great or horrible.

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Wolves can be a disaster for ranchers because they create chaos around the ranch. Chasing, killing, and stressing out livestock, as well as other potential issues. The wolves in the park aren't trapped by its boundaries; they're known to travel outside it.

Not having wolves in Yellowstone could lead to a drop in tourism, putting financial pressure on the industry. The National Park Service once estimated that nearly $35 million in tourism dollars is brought in annually from wolf watchers alone.

The Science Daily report is now asking whether wolves have as great an impact on the park's ecosystem as previously believed, based on research released in 2025. The subject of the research: The growth of Willows. Yes, you read that right. The willow is making a huge comeback, and some scientists think it's due to the wolf.

Some researchers believe data from a 20-year study shows that the willow height surge of 1500% is directly due to the reintroduction of wolves into Yellowstone. The research says that trophic cascades are the indirect effects passed down by predators. They believe that when the wolves returned, the elk population declined, thereby improving willow growth.

In a more recent study, scientists challenged some aspects of the earlier report and say wolves are important, but maybe not as important as previously thought. Dr. Daniel MacNulty, lead author and wildlife ecologist at Utah State University, explained in the Science Daily report:

Ripple et al. argued that carnivore recovery produced one of the world's strongest trophic cascades, but our re-analysis shows their conclusion is invalid because it relies on circular reasoning and violations of basic modeling assumptions.

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 the report, the concerns of the previous study were that the height-to-volume model showed discrepancies, the willow plots in the 20-year study were in different locations, not all trophic cascades are created equally, and that human hunting was not factored in. The researchers aren't saying that wolves aren't important; they're saying that they want to clarify the evidence.

The new paper helps explain why scientists analyzing the same dataset reached different conclusions. Ripple et al. (2025) described wolf recovery as triggering a powerful trophic cascade. In contrast, Hobbs et al. (2024), who gathered the data during 20 years of field experiments, reported only weak cascade effects.

See, no one can agree on the impact wolves have on Wyoming. Some say YAY, they're great, some say NAY, they're horrible, some say wolves caused willow growth, and some say no, they didn't. It's a debate no one will ever win.

It is pretty cool to see them in their element.