Yellowstone wolf study faces challenge over overstated ecological impact
8 reported1 conflicting
A new peer-reviewed analysis published in Global Ecology and Conservation argues that a high-profile 2025 study significantly overstated the ecological impact of wolf recovery in Yellowstone National Park. Researchers from Utah State University and Colorado State University say the earlier work relied on flawed methods that led to exaggerated conclusions about how wolves affected the park’s ecosystem. The analysis focuses on a claim that willow crown volume increased by 1,500 percent following wolf recovery, which the authors say was derived from a statistical model using circular reasoning. The researchers also identified other concerns, including the application of a height-to-volume model to heavily browsed willows with unusual growth forms and the comparison of different willow plots between 2001 and 2020. After accounting for these issues, the authors conclude there is no evidence for a dramatic, park-wide increase in willow growth, instead supporting a more modest and spatially variable response. The team emphasizes their findings should not minimize the ecological importance of large predators but highlight the need for rigorous methods.
What’s reported
A new peer-reviewed analysis in Global Ecology and Conservation challenges a 2025 study on Yellowstone wolf impacts.
Researchers from Utah State University and Colorado State University conducted the analysis.
The 2025 study claimed willow crown volume increased by 1,500 percent after wolf recovery.
The new analysis says the 2025 study used a statistical model with circular reasoning, using plant height to both calculate and predict willow volume.
Other concerns include applying a height-to-volume model to heavily browsed willows with unusual growth forms and comparing different willow plots between 2001 and 2020.
The analysis argues that comparisons with global trophic cascades used equilibrium assumptions not fitting Yellowstone’s non-equilibrium ecosystem.
The authors conclude no evidence supports a dramatic, park-wide increase in willow growth from wolf recovery.
The analysis notes that Ripple et al. (2025) interpreted data as a powerful trophic cascade, while Hobbs et al. (2024) reported only weak effects.
Conflicting accounts
The source article describes conflicting interpretations of the same dataset: Ripple et al. (2025) interpreted data as evidence of a powerful trophic cascade, while Hobbs et al. (2024) reported only weak trophic cascade effects. The new analysis argues the evidence points to a more limited and variable ecological response.
Key figures
Dr. Daniel MacNulty, lead author of the new analysis and wildlife ecologist at Utah State University
Dr. David Cooper, co-author of the analysis and emeritus senior research scientist at Colorado State University
Michael Procko, co-author
T.J. Clark-Wolf, co-author
Sources: ScienceDaily
