6.10.3. Natural Terrestrial Ecosystems
Most climate models agree that a reduction in the equator to pole temperature gradient, at least on land, will be experienced in a greenhouse world. Consequently, climatic zones could shift several hundred kilometres towards the poles during the next century (Emmanuel et al., 1985), although the rate of transition is uncertain. As flora and fauna would lag behind these climatic shifts, they would be subject to considerable stresses. Many species may be unable to adapt to different climatic and meteorological regimes, and will become extinct.
The rate of projected climate changes is critical in determining the nature of impacts on terrestrial ecosystems and their ability to adapt. Even a projected temperature increase of 0.2�C per decade (Hadley Centre, 1995) is at least twice the maximum rate of increase that most ecosystems could withstand (IPCC, 1990b). The most susceptible ecological systems will include montane, alpine, polar, island and coastal communities where climatic changes will add to existing stresses.