The magnitude of climate changes forecast for the next century is comparable to the magnitude of warming during the last deglaciation. No climate change of similar magnitude has occurred since that event. The palaeoecological evidence of the response, especially of plants, to past climate change indicates that evolutionary adaptation has played no more than a minor role and that migration is the usual response of organisms to climate change. The individualism of response has important implications with respect to changes in the nature of vegetation and ecosystems. The maximum realized rates of migratory response by trees, although perhaps matching the maximum potential rates, are close to the maximum that it is believed can be achieved by such long-lived sessile organisms. The rate of climate change forecast for the future is 10–100 times faster than the rate of deglacial warming. Unless steps are taken to facilitate the migratory response of organisms to the forecast changes, then widespread extinction is likely. Artificial dispersal of trees and other organisms of limited dispersal and/or migratory capacity, the general extension of the legal protection currently afforded to some threatened organisms only within designated reserves, and the integration of wildlife habitat requirements and of wildlife corridors into human landscape utilization are all likely to be necessary. Stringent measures to limit the extent of future climate change by limiting emissions of greenhouse gases will also be necessary if the possibility of widespread and even catastrophic extinction is to be avoided.