The refugium concept looks simultaneously backward toward more favorable conditions of the past, and forward toward a temporary or permanent future of less favorable conditions than the present. Refugia are spatially referenced, but operationally defined in terms of their ability to sustain populations of particular species or other features sensitive to environmental change. Existence of refugia is made possible by spatial heterogeneity in the environment: refugia represent deviations from the typical environmental conditions in a region.
Application of the refugium concept in context of conservation and resource management can be enhanced by further development of robust conceptual frameworks. What is the dependency of refugia on spatial heterogeneity of the physical environment, modulation of the physical environment by vegetation and other biotic entities, and the ecological processes and dynamics that allow refugial populations to persist? Can environmental change lead to net flattening or sharpening of environmental heterogeneity? Can extreme disturbance events lead to a flatter world with net loss of refugial sites? How long are individual refugia likely to persist under climate change? Did today’s refugia serve in the past as refugia for other species? Can they serve similarly for other species in the future?
Results/Conclusions
Consideration of past, present, and future refugia in broader context of environmental change can address these questions and develop more robust frameworks for application. Paleoecological studies indicate that, although refugial populations can sometimes persist in the face of major climatic changes over multiple millennia, other refugial populations are ultimately doomed to extinction. Although today’s refugium may be tomorrow’s grave for a particular species population, it may also serve as tomorrow’s refugium for another species. Environmental change will lead to transient and often novel assemblages of movers and stayers (sensu Hobbs et al. 2017, TREE), and in this context refugia can facilitate both persistence and movement. Understanding how environmental heterogeneity may respond to environmental change can guide planning, design, and management towards robust networks of protected or managed sites, including refugial archipelagoes in which refugial sites are handed off from one species to another. Refugia applications generally emphasize the eroding tail of a shifting environmental gradient. However, sites at the expanding tail can serve as colonization centers for immigrants better adapted to emerging conditions. Such ‘inverse refugia’ can be managed to facilitate transition to ‘new normals’ as the environment changes.