Farming systems are essential to human well-being as they supply the bulk of humanity's food and fibre. They also cover a large portion of the Earth's land area and many are already threatened by damage to soil and water resources through inappropriate technology. Major changes in land-use, which are currently the main manifestation of global change, will greatly increase these stresses, driven by increasing demands for agricultural and forest products from a growing population. Climatic and atmospheric changes – the other major aspects of global change – will have further impact upon these rapidly changing systems in ways which cannot yet predict with any accuracy. The ability to capitalize on the beneficial effects of global change, while avoiding or reducing adverse environmental effects, requires a strong predictive capability.