Preventing extinction in an age of species migration and planetary change

International and national conservation policies almost exclusively focus on conserving species in their historic native ranges, thus excluding species that have dispersed on their own accord or have been introduced by people. Given that many of these ‘migrant’ species are threatened in their native ranges, conservation goals that explicitly exclude these migrant populations may overlook opportunities to prevent extinctions and respond dynamically to rapidly changing environmental and climatic conditions. Focusing on terrestrial mammals, we quantified the extent to which migration, in this case via introductions, has provided new homes for threatened mammal species. We then devised alternative scenarios for the inclusion of migrant populations in mainstream conservation policy with the aim of preventing global species extinctions and used spatial prioritization algorithms to simulate how these scenarios could change global spatial conservation priorities. We found that 22% of all identified migrant mammals (70 species) are threatened in their native ranges, mirroring the 25% of all mammals that are threatened. Reassessing global threat statuses by combining native and migrant ranges reduced the threat status of 23 species (∼33% of threatened migrants). Thus, including migrant populations in threat assessments provides a more accurate assessment of actual global extinction risk among species. Spatial prioritization simulations showed that reimagining the role of migrant populations to prevent global species extinction could increase the importance of overlooked landscapes, particularly in central Australia. Our results indicate that these various and non-exhaustive ways to consider migrant populations, with due consideration for potential conservation conflicts with resident taxa, may provide unprecedented opportunities to prevent species extinctions. We present these alternatives and spatial simulations to stimulate discussion on how conservation ought to respond, both pragmatically and ethically, to rapid environmental change in order to best prevent extinctions. ### Competing Interest Statement The authors have declared no competing interest.