Assisted migration is a conservation approach taken in an attempt to thwart the climate-induced extinction of the endemic Florida Torreya. Since the translocation of the Florida Torreya is easy, legal and cheap (McLachlan et al, 297), the convenience of this assisted migration raises concerns of its potential unintended consequences. In order to address those concerns, a scientifically based policy should be formulated. The article mentions 3 positions that explain choices in formulating policy and conflicts among these perspectives (McLachlan et al, 297).
Advocates of aggressive assisted migration believe that human assistance is necessary and the projections of climate-driven habitat shifts are accurate (McLachlan et al, 298). Policy consistent with this position is likely to endorse broad applications of predictive habitat models to many species, extensive species translocation, and restoration-style establishment. Aggressive assisted migration may be best for minimizing species loss under rapid climate change, but it also implies higher risk of disruption on existing communities (McLachlan et al, 298). Thus, proponents of this policy are associated with a high-perceived risk of inaction and high ecological confidence (McLachlan et al, 299). In contrast, opponents of assisted migration have a high-perceived risk of action and low ecological confidence. They tend to focus on the unintended consequences of species translocation, the complexity of what controls population dynamics of species, the uncertainty in climatic predictions, lack of data for modeling species’ climatic envelopes, the problem of the assumption of species’ uniform climatic tolerances, and the problem of incorporating biotic interactions in determining species’ susceptibility to climate change (McLachlan et al, 299). Since avoidance of assisted migration implies higher risk of climate-driven extinction, policy consistent with position 2 must stress facilitating natural population spread and preserving isolated populations (McLachlan et al, 299). On the other hand, advocates of constrained assisted migration have relatively low perceived risk of inaction and low ecological confidence. They expect that assisted migration is necessary and that careful planning and adaptive management can minimize recognized risks (McLachlan et al, 299). Thus, evidence of imminent threat, an outcome-predicted model, and a management plan maybe required in assisted migration proposals. Since such a migration plan would need to be informed by scientific information, it could impose high costs (McLachlan et al, 299).
Ecological research on estimation and monitoring of species distributions, biogeographic modeling, community interactions, long-distance dispersal (LDD), genetic diversity, are needed to inform assisted migration policy. Programs that monitor species response to climate change and information about species distributions are needed. Methods and accuracy of biogeographic models should be improved, as models tend to overemphasize risk and movement potential of narrowly distributed species, due to the assumption that their current distributions are climatically constrained (McLachlan et al, 300). Species interactions should also be taken into consideration when determine species’ range limits. Research on species interactions may reveal novel interactions, indirect effects and their time lags, and source populations (McLachlan et al, 300). Improved LDD estimates are important for predicting which species require an assisted migration and for estimating the likeliness of future species dispersal into areas made available by climate change (McLachlan et al, 300-301). Research on genetic diversity would help assisted migration programs choose source populations wisely, as some populations’ genotypes may be most threatened by climate change while other populations’ genotypes are more suitable for the introduction to new environments (McLachlan et al, 301).
