With habitat fragmentation and projected rates of climate change, some species could face extinction if they cannot reach high-quality habitats in climates within their physiological limits in the future. One strategy to prevent the extinction of these species is assisted migration, the purposeful relocation of species beyond their historical ranges. Because it is usually presented as a single-species approach, assisted migration is often contrasted to several alternatives management strategies that could conserve entire communities of climate-shifting species. In particular, increasing connectivity, restoring low-quality habitats, and preserving existing high-quality habitats might also benefit climate-threatened species, provided they can reproduce and disperse quickly enough to track climate change. To evaluate the effectiveness of each of these alternatives in a variety of communities and environments, we modeled the climate-tracking of randomized competitive metacommunities with several alternative management interventions. In each landscape, we represented habitat fragmentation by varying the carrying capacity over space, including the size of low-quality sinks and high-quality sources. To compare management strategies in different environments, we also randomized the local climate heterogeneity and the magnitude of environmental stochasticity.
Results/Conclusions
On average, corridor establishment and assisted migration were the most effective alternatives at retaining the alpha and gamma diversity in the metacommunities experiencing climate change. Though assisted migration typically led to the greatest reduction of extinction likelihood for short-dispersing species (and the only strategy to do so in unfragmented landscapes), it could require extensive management effort in moving several species multiple times. In general, the effectiveness of each management strategy was sensitive to small increases in management effort with diminishing returns with higher effort. Moreover, all strategies effectively conserved species in competitive environments where poleward competitors could otherwise block equatorward species from tracking climate change. Overall, assisted migration could be an effective multi-species approach as long as there are only few dispersal-limited species in a competitive community and low risk from factors that we did not model (such as pathogen transport). Given similar biodiversity protection performance between assisted migration and traditional methods for increasing connectivity, the optimal approach will then depend on the capacity to implement these strategies and tolerance for additional risks they might incur.