Assisted migration of forest populations for adapting trees to climate change

We present evidence that climatic change is an ongoing process and that forest tree populations are genetically differentiated for quantitative traits because of adaptation to specific habitats. We discuss in detail indications that the shift of suitable climatic habitat for forest tree species and populations, as a result of rapid climatic change, is likely to cause significant stresses to natural tree populations. Due to the physical limits of natural migration, tree populations will be unable to keep pace with the moving target that their suitable climatic habitat will become. The consequent decoupling between natural populations and the climate for which they are adapted, will likely cause large forest decline, a phenomenon that is already underway in several forests of the world. In order to accommodate climate change, what are our forest management options? What would be the consequences of inaction? We describe and discuss assisted migration, which is the physical realignment of natural populations to the climate for which they are adapted, by reforestation in sites where their suitable climate is predicted to occur in the future, as an active management option with the aim of maintaining healthy tree ecosystems in the future.