Natural Resource Ecology Laboratory

Important Research Findings

Alternative states and food web structure:

The restoration of large predators to ecosystems may fail to reverse conditions in plant communities created by their loss from those ecosystems. We have been working for a decade to understand the effects of of the reintroduction of wolves to the northern range of Yellowstone National Park. The loss of wolves from the northern range caused a state change in riparian plant communities as result of excessive browsing by a population of elk unregulated by predation after the extirpation of wolves in the early 1900’s . Part of that state change was the loss of dam building activity by beaver. We have shown that the changes in hydrologic conditions caused by the absence of beaver-mediated disturbance has stabilized the alternative state such the reintroduction of wolves has largely failed to restore the riparian community to pre-wolf conditions.

The role of native predators in reindeer population dynamics:

Contemporary efforts to protect biological diversity recognize the importance of sustaining traditional human livelihoods, particularly uses of the land that are compatible with intact landscapes and ecologically complete food webs. However, these efforts often confront conflicting goals. For example, conserving native predators may harm pastoralist economies because predators consume domestic livestock that sustain people. This potential conflict must be reconciled by policy, but such reconciliation requires a firm understanding of the effects of predators on the prey used by people. We used a long-term, large-scale database and Bayesian models to estimate the impacts of lynx (Lynx lynx), wolverine (Gulo gulo), and brown bear (Ursus arctos) on harvest of semi-domesticated reindeer (Rangifer tarandus) by Sámi pastoralists in Sweden. We showed that native predators meaningfully reduce the harvest of reindeer by the Sámi, providing a scientific justification for policy aimed at compensating them for losses of their animals to predation.

Effects of habitat fragmentation on consumer population dynamics:

Fragmentation of landscapes is a pervasive source of environmental change. Although understanding the effects of fragmentation has occupied ecologists for decades, there remain important gaps in our understanding of the way that fragmentation influences mobile organisms. In particular, there is little tested theory explaining the way that fragmentation shapes interactions between consumers and resources. We propose a simple model that explains why fragmentation may harm consumers even when the total amount of resources on the landscape they use remains unchanged. In particular, we show that nonlinearity in the relationship between resource availability and benefits acquired by consumers from resources can cause a decrease in benefits to consumers when landscapes are subdivided into isolated parts and when the distribution of consumers in fragments is not matched to the distribution of resources.