Assisted migration (AM) has been suggested as a conservation strategy for aiding species to reach newly suitable locations as climate changes. The magnitude of decrease in range size and the extent of emerging new areas can be used to guide decisions on the applicability of AM. However, before our studies it had not been formalized how predictions of changes in suitable areas, acquired using e.g. species distribution models (SDMs) or expert assessments, should translate into management decisions. We presented a conceptual framework for identifying situations in which projections from such predictions indicate that a species could benefit from AM. We translated predicted changes in suitable area into separate quantitative metrics for migration need and migration potential on the basis of the amount of lost, remnant, and new area.

We apply the method using outputs of consensus SDMs that forecast the future suitable areas for 13 vascular plant species with poor dispersal capacity under different climate change scenarios and future times. Based on the predicted changes in suitable area for the species, and the metrics for the need and potential for AM calculated thereof, we found substantial differences in the number of species benefitting from AM under different climate change scenarios. By the end of the 21st century only one of the species would benefit from AM under mild climate change, while for all but one of the studied species AM appears to be a useful conservation method under strong climate change.

We also tested the effect of different modeling attributes on the metrics and find little variation between SDMs constructed using different combinations of modeling methods. However, the choice of climate variables had a larger influence on the level of the metrics. We therefore suggest that the choice of climate variables should receive ample attention when measuring climate change threat through SDMs, both for AM and in general. Moreover, experiments aiming to uncover critical environmental factors for individual species should be executed extensively enough. Nevertheless, as illustrated by our results, dispersal assistance may be needed for many species under a wide range of possible future climates; the presented metrics have potential to aid the screening of multiple species for identifying AM-candidates as part of broader decision-making frameworks.