SIESTR: a novel method to analyze Species’ Introductions Effects in Space and Time on Range dynamics

Rapidly shifting climates will lead to species range shifts over the next century. Artificially introducing species in new locations to enhance species migration, termed assisted migration (AM), has been suggested as one possible strategy to avoid species extinction. While current models of range shift are used to explore potential future areas of introduction, we lack a method able to identify the best sets of locations and timing for species introductions that maximize AM outcomes. We developed a novel method to explore the effects of Species’ Introduction Effects in Space and Time on Range dynamics (SIESTR). The method uses transition matrices that combine spatial and temporal species’ environmental suitability changes and dispersal information. A metaheuristic algorithm is run to achieve an objective target of range area optimizing locations and times of species introductions, while minimizing spatially explicit cost surfaces. We apply the method to a virtual species to showcase the potential of SIESTR to explore the maintenance of range size under climate change via artificial introductions. We assess optimal AM strategies under climate change and with different land use cost scenarios. We found a strong effect of early introductions enhancing species range shifts, as well as differences in introduction sites and timing under different cost scenarios. SIESTR is a fast and efficient technique for exploration of range shifts under artificial introductions, tackling both the spatial and temporal dimensions. The method has been developed in Cpp, available as an R package. Given the heated debate around AM and introductions, our method provides a new tool to explore strategies in spatial conservation planning in the Anthropocene.