Anthropogenic climate change threatens many species, but especially those that cannot track rapid climate velocities. During past periods of rapid climate change, some species persisted in climate refugia, or areas with low or heterogeneous climate velocities. While many communities of species may have assembled under traditionally heterogeneous conditions, human impacts have made current ecosystems more homogeneous in climate velocity than they have been previously. Therefore, previous climate refugia might no longer be available. We quantify the potential efficacy of restoring heterogeneity in the habitats of species that are especially threatened by climate change. We built a stochastic model to simulate the climate-tracking of competing species in a randomized metacommunity over an environment undergoing climate change. In this model, each species concurrently cycles through reproduction, dispersal, and competition over limited space. Temperature change is stochastic over time, but locally dependent on environmental heterogeneity. We used this model to explore the effects of climate velocity heterogeneity on both community assembly and potential changes in community composition through projected climate change. Additionally, we used this model to examine the impact of increasing heterogeneity in climate velocity on future community composition.
Results/Conclusions
With different levels of environmental stochasticity and heterogeneity in climate velocity, we assembled several interacting communities where anthropogenic homogenization has occurred for a long enough time that communities are near equilibrium. We found that the communities that assembled in homogeneous environments were less diverse and had species with narrower ranges, lower population sizes, and higher dispersal ability on average than communities in more heterogeneous environments. After subjecting these communities to climate change, we found mixed implications for homogeneous environments because species with low ranges and population sizes were more likely to go extinct, but species with long dispersal were more likely to survive. Increasing the climate velocity heterogeneity of these previously homogeneous environments decreased extinction probability and increased species’ range and population size. This is likely because increasing heterogeneity in climate velocity reduced the distance that species needs to disperse to reach future analog climates. Next, we are assembling communities where anthropogenic change is recent enough that community dynamics are adjusting toward equilibrium conditions. In such cases, increasing heterogeneity might rescue species already declining toward extinction regardless of climate change. Overall, increasing heterogeneity in climate velocity might create climate refugia that enhance species persistence and community diversity during climate change.