Vegetation and climate

Over the last two centuries, man's activities have caused a 30% increase in the atmospheric concentration of CO 2, with continued increases seeming inevitable. This change in CO 2 concentration will act on vegetation, both directly and indirectly through global climatic change. It is well established that, on a global scale, patterns of vegetation and climate are closely correlated. Such correlations indicate that climatic change will cause the distribution of vegetation to change. However, the use of correlations for predicting vegetation responses to climatic change is fundamentally unreliable because correlations have no mechanistic underpinning of causation. This paper outlines a mechanistic model for predicting the equilibrium state between current climate and vegetation. It is also used to indicate the sensitivity of global vegetation to the changed climate associated with a doubled CO 2—greenhouse scenario. The interpretation of this static model is discussed in terms of rates and patterns of vegetation change.