Recent findings by a team of researchers led by Dr. Daniel R. MacNulty challenge a widely publicized assertion regarding the ecological impact of wolf reintroduction in Yellowstone National Park. The claim that the recovery of carnivores has resulted in one of the strongest trophic cascades globally is now under scrutiny. This new research required painstaking data collection over a twenty-year span. It indicates that the plant life impacts of wolf reintroduction are considerably more overblown than once claimed.
Dr. MacNulty, a wildlife ecologist at Utah State University, was principal investigator on the first-of-its-kind study. He joined together with co-author Dr. David Cooper, an emeritus senior research scientist at Colorado State University. Their work has been at the forefront of measuring how the reintroduction of wolves has changed patterns of vegetation across northern Yellowstone National Park.
In order to assess wolves’ effects, the researchers set up field experiments and collected vegetation data over two decades. This intensive, six-year-long study provided the first opportunity to look at the bottom-up influence of wolf predation on plant communities. In particular, it addressed the population dynamics of willow (Salix spp.). In fact, surprisingly, these analyses showed only nominal evidence of cascade effects, contrary to previous assertions of a large-scale ecological revolution.
An earlier study modeled willow crown volume with a multiple regression model. We were staggered to see the results were an incredible 1,500% increase since the reintroduction of wolves. This model takes diameter and plant height data and calculates/predicts total volume. It operates on the assumption that willow crown geometry conforms to a half-ellipsoid crown morphology. As Dr. MacNulty noted, this geometric assumption is a poor representation of willow plant structure in reality. Field photographs along with geometric reference diagrams helped provide strong proof of such a disparity.
The inconsistencies were compounded by comparisons of willow data taken between 2001 and 2020. Fulfilling an opportunity During this period, the researchers found the willow plots to be largely unmatched. This is a serious addressable flaw to the original analysis supporting this strong trophic cascade claim. Dr. MacNulty pushes back against the assertion that wolf reintroduction has produced a robust trophic cascade in Yellowstone’s ecosystem. He contends that this claim is false.