Predicting population, species, and community responses to climate change requires understanding conditions at scales where individual physiological stresses are realized. In many cases, we still have poor understanding of how microhabitat conditions respond to larger-scale climate forcing. This is particularly problematic given the large fraction of biodiversity residing in facilitative microhabitats that can dramatically alter environmental conditions. We use intertidal mussel beds as a model system to address the question of how facilitative microhabitats may alter climate warming projections for dependent taxa. First, we characterize how the mussel matrix modifies external climate parameters that impose heat and desiccation stresses. We couple these data with field exposure experiments to identify physiological tolerances of common bed inhabitants (the isopod Cirolana harfordi and the porcelain crab Petrolisthes cinctipes). We then examine how mortality risk shifts with climate change inside and outside the facilitative habitat by constructing an empirically derived model of evaporation and simulating mortality risk under a hot-dry (business-as-usual) climate-change scenario through 2099.
Results/Conclusions
Results revealed that the facilitative microhabitat so effectively buffered external climate conditions that mortality risk from thermo-desiccation stresses remained negligible and largely unaffected by even a severe future-warming scenario. We also found that heat-exacerbated desiccation in the field drove 100% mortality in both species at temperatures 4.4 to 8.6 ºC below their strict thermal tolerances under fully hydrated laboratory conditions. These findings underscore the importance of heat-exacerbated desiccation as a key stressor under climate warming, with the potential to dramatically increase mortality risk. Our results imply that stress-ameliorating habitats can reduce the likelihood of direct effects of climate warming for the many species occupying stress-ameliorating habitats. Rather, climate change risk for such taxa is likely to be indirect and intimately linked with the integrity of biogenic habitat structures. Taken together, our results provide evidence that habitat conservation and restoration could help support biodiversity resilience in the face of climate warming by providing refugia from both heat and desiccation stresses, at least in the near-term.
