Managed relocation: A nuanced evaluation is needed

Managed relocation (aka ‘assisted colonization’ and ‘assisted migration’) aims to save species from the effects of climate change by purposefully transporting them to areas where they have not previously occurred, but where they are expected to survive as temperatures increase. In a recent Opinion article in TREE, Ricciardi and Simberloff suggest that ‘assisted colonization is tan- tamount to ecological roulette and should probably be rejected as a sound conservation strategy by the precautionary principle.’ We disagree for three primary reasons. First, the precautionary principle is not a stand-alone reason to rule out managed relocation. Second, we know more about the impacts of species invasions than Ricciardi and Simberloff suggest, particularly with respect to species extinction. Third, because extinctions are premanent and irreversible, using managed relocation to reduce extinctions at the cost of changing the composition and functioning of ecosystems is a tradeoff that some managers might be willing to make. Ultimately, the risk of species extinctions from climate changes is too large to summarily discount managed relocation without first carefully evaluating its benefits and dangers in a nuanced way.