As regional climates shift faster than many slow-dispersing species can track on their own, some conservation biologists have proposed 'assisted migration': deliberately relocating a population to a site outside its historical range but within the climate envelope it is projected to require within decades. Proponents argue that without intervention, such species face near-certain local extinction as their current habitat becomes climatically unsuitable before they can disperse to a new one unaided.

Critics warn that assisted migration risks introducing a new species into an ecosystem it has never occupied, where it may compete with, prey upon, or transmit novel pathogens to resident species that have no evolutionary history of exposure to it—effectively trading a predictable, single-species loss for an unpredictable, ecosystem-wide risk. They note historical cases in which species deliberately introduced for other purposes, such as biological pest control, became destructive invaders once established outside their native range.

Proponents respond that the relevant comparison is not between assisted migration and doing nothing in the abstract, but between two specific outcomes: the near-certain loss of the target species if left in place, weighed against the risk—difficult but not impossible to estimate in advance through controlled trial introductions on a small scale—that the relocated population disrupts its new ecosystem. Where trial introductions can be conducted and monitored before a full-scale relocation, they argue, the ecosystem-risk critics raise can be substantially reduced without abandoning the intervention.