Current projections of climatic change call for a global average temperature increase of 2.8 to 5.2 C and a 7% to 16% increase in rainfall by about 2030. The potential ecological responses to these changes have been estimated using a variety of techniques, but have generally been restricted to relatively small scales. More recently, the global response of terrestrial ecosystems has been estimated using the steady-state correlation approaches of Holdridge and Box. Double-CO2 climatic scenarios applied to these approaches suggest that the temperature and boreal ecosystems could be displaced toward the poles by hundreds of kilometers. The spatial displacement of extratropical biomes could range from about 50% to near 90% of their current latitudinal extents.