Continental-scale identification and prioritisation of potential refugee species; a case study for rodents in Australia

A species is expected to be most resilient to environmental change when it occurs across a broad diversity of habitats. However, there is often no visual representation of the past (i.e. prehistoric and historical) context for a species in the range maps published by national and global authorities. Therefore, it is easy to overlook the fact that many species once occupied a broader geographic range, or greater diversity of habitats. Such oversights hinder the effective conservation of species that have become restricted to a subset of their formerly occupied habitats. Here, we quantified the shifted baseline that may underpin some of the ecological misconceptions about species, and developed a rapid assessment method to aid the identification and prioritisation of ‘potential refugee species' (i.e. species that have become restricted to a subset of their formerly occupied niche). The assessment of potential refugee status is different from, but complementary to, the International Union for Conservation of Nature (IUCN) Red List and Green Status frameworks. Our framework defines a continuum of potential refugee status, which was demonstratable in continent-scale maps drawn from biogeographic regionalisation. Applying this framework to all native rodent species across the continent of Australia (a group that has suffered several extinctions and notable declines), we found that the risk of ecological misconceptions caused by shifted baselines (i.e. resulting from ‘shifting baseline syndrome') was prevalent. This suggests that in many cases, translocation opportunities that might be avoided because they are perceived as conservation introductions (as defined by the IUCN translocation guidelines), may in fact fall within the indigenous range, and should therefore be considered reasonable reintroductions. Ultimately, our potential refugee assessment framework will help to facilitate the undertaking of ambitious translocations that will build species' resilience to environmental change by resuming their adaptation to habitats across all formerly occupied bioregions.