Optimal timing for managed relocation of species faced with climate change

Managed relocation is a controversial climate-adaptation strategy to combat negative climate change impacts on biodiversity. While the scientific community debates the merits of managed relocation1–12, species are already being moved to new areas predicted to be more suitable under climate change13,14. To inform these moves, we construct a quantitative decision framework to evaluate the timing of relocation in the face of climate change. We find that the optimal timing depends on many factors, including the size of the population, the demographic costs of translocation and the expected carrying capacities over time in the source and destination habitats. In some settings, such as when a small population would benefit from time to grow before risking translocation losses, haste is ill advised. We also find that active adaptive management15,16 is valuable when the effect of climate change on source habitat is uncertain, and leads to delayed movement. Rapid climate change is leading to shifts in the distribution of many species17–22 and will have economic and social consequences for human societies23,24. Predicting the impact of different climatechange scenarios on biodiversity has been the overwhelming focus of research effort so far21,25; far less attention has been devoted to developing and choosing between adaptation actions for biodiversity management. Managed relocation (also known as assisted colonization) is a controversial adaptation action for combating the impacts of climate change on biodiversity1–12 and has recently been identified as a key priority for conservation research26. Managed relocation involves physically moving species from habitat predicted to become unsuitable under climate change to locations where the habitat is predicted to become suitable, but where they have never occurred before. At present, debate is focused on whether to undertake managed relocation, in light of its potential risks and benefits2,5,9,11. While this debate continues, species are being moved in anticipation of the risks of climate change13,14. There is now an urgent need for a framework to underpin decisions about when to implement managed relocation, a framework that recognizes the potential for learning to reduce uncertainty and improve future decisions.