Determining the potential distribution of vegetation, crops and agricultural productivity

The terrestrial biosphere component of the Integrated Model to Assess the Greenhouse Effect (IMAGE 2.0) uses changes in land cover to compute dynamically the greenhouse gas fluxes between the terrestrial biosphere and the atmosphere. Potential land cover for both natural ecosystems and agrosystems, are determined with the Terrestrial Vegetation Model (TVM). TVM consists of separate submodels for the water-balance, global vegetation patterns, crop distribution and potential rain fed crop yield. All these submodels are based on local climatic, hydrological and soil characteristics and appropriate global data bases for those parameters are collected or compiled. The structure of all models, data bases and linkages between them and other modules of IMAGE 2.0 are described. Although computationally demanding, the models give an adequate description of the global vegetation and agricultural patterns. The only discrepancy occurs in regions where the vegetation and agricultural distribution depends on causes other than climatic, such as additional water storage and supply, anthropogenic influence and natural disturbance. Despite this discrepancy, we conclude that TVM simulates satisfactory global vegetation characteristics and that it can be adequately integrated with other models of IMAGE 2.0