The past, present and future impacts of climate and land use change on snowshoe hares along their southern range boundary

Changes in land use and climate are among the main drivers of range shifts for multiple species and taxa. While such distributional changes are often observed at broad scales, the processes driving them – colonization and extinction along range boundaries – occur at local scales. There is a need then, to identify whether these local drivers are consistent with patterns at broader scales. Snowshoe hares (Lepus americanus), an important prey species in northern forest ecosystems, have experienced range contraction along much of their southern boundary. Population declines are linked to climate change via camouflage mismatch, an inability to match seasonal coat color molts with declining snow cover duration. We used data from camera traps to monitor the spatial extent and habitat associations of hares before, during and after an experimental translocation, and multi-season occupancy models to model the effects of habitat and climate on colonization and extinction patterns. We compared our contemporary occupancy models to historical patterns of extirpation and simulated future effects of timber harvest on occupancy. Colonization by hares was strongly associated with distance from source population and patch size of aspen-alder. Historical patterns of extirpation were consistent with contemporary patterns, and simulations revealed that increased frequency and magnitude of aspen harvest increased hare occupancy by creating large patches of early-successional habitat. As global change alters ecological communities, identifying mechanisms that drive range-shifts and targeting landscape features that can be manipulated to buffer those effects can be used to promote the persistence of individual species and ecological communities.