A species is expected to be most resilient to future environmental change when it occurs across a broad diversity of ecosystem types. However, despite increasing recognition of the importance of prehistoric records, it remains easy to overlook the fact that many species once occupied a broader range, or greater diversity of ecosystem types, than is indicated by their current distribution. Such oversights hinder the adaptive capacity and effective conservation of species that have become restricted to a subset of formerly-occupied ecosystem types. In a study of all native rodent species in Australia (a group that has suffered several extinctions and notable declines), we interpret patterns in extents inferred from the overlay of bioregions, occurrence records (including subfossils), and current distributions as a measure of the shifting baseline syndrome described above. We propose that this measure could aid the identification and prioritisation of actions for “potential refugee species” (i.e., species suspected of being restricted to a realised niche that is suboptimal for individual fitness). The potential refugee status is different from, but complementary to, a species’ IUCN Red List status. Incorporating national vegetation mapping into the inferred extents, a broad scope for potential restoration opportunities can be derived to aid conservation efforts. Ultimately, our aim is to encourage and facilitate the undertaking of a diversity of translocations so that species’ adaptations to a broad range of ecosystem types (including climates) can resume.