The role of modelling in the quest for sustainable farming systems

Sustainability in agriculture involves inter-temporal tradeoffs in the use of natural resources. Analysis of sustainability necessarily involves the study of the dynamics of change in the stock of natural resources. To understand and analyse sustainability better it is important to be able to forecast the future consequences of current resource-use decisions. As the time frame involved may be long, and complex interactions among various parts of the farming systems need to be well understood, modelling is a good tool for studying such phenomena. Following consideration of the role of various types of models of farming systems as substitutes for, or complementary to, real-world experimentation, it is contended that bio-economic simulation models are well-suited for studying sustainability. A powerful tool to evaluate sustainability implications of alternative management practices is provided by the framework of optimal control theory. Some illustrative applications of modelling are presented and possible problems in applying such models in the context of developing countries are presented.