Emissions of greenhouse gases from the burning of fossil fuels are altering Earth's climate. This human-driven (anthropogenic) climate change (or “global warming”) presents yet another threat to species' survival. The current episode of global climate change has caused measurable geographic shifts in climate zones, principally poleward and upward. Many wild species are already showing changes in their distributions that are, to varying degrees, tracking the shifting climate zones.

One of the main conservation concerns is that, as climate zones shift across the landscape, our current preserve network will no longer contain appropriate climates for the species for which those preserves were designed. Furthermore, human domination of the landscape creates barriers to natural movements of species toward new geographic areas that have only recently become climatically suitable. If species within preserves (or other undisturbed habitats) experience degradation of their local climate, their natural dispersal abilities may be insufficient to allow them to cross agricultural lands and urban areas to successfully colonize newly formed habitats outside their current range. In these situations, it has been suggested that human-assisted translocation of individuals, often termed “assisted migration” or “assisted colonization,” may be necessary to ensure colonization of new geographic regions as parts, or all, of the species' historic range becomes climatically unsuitable.