The dynamics of vegetation change: health warnings for equilibrium 'dodo' models

Vegetation plays a part in controlling climate and in turn responds to climatic change. Therefore, projections of future climates must include the responses of vegetation, both in terms of function and distribution. Unfortunately, assessments of future climatic impacts on vegetation are still considered with equilibrium vegetation models-models which exclude processes involved in vegetation dynamics, such as succession and disturbance. The commonly held view that future spatial changes in temperature will outstrip the potential for species to migrate has no theoretical underpinning, particularly as the important processes of disturbance and tolerance of climatic change are not included. In order to assess the appropriate rates of vegetation change it is necessary to implement dynamic vegetation models. Such models are now bring completed but provide their own problems associated with the inclusion of poorly understood processes and with methods of testing.