An alternative is crop yield analysis, which is conducted for specific crops and is usually more sophisticated than resource-rating schemes, being based on interactions among crop growth factors and generating estimates of output per land unit (Baethgen and Magrin, 1995). The outputs from crop yield analyses have produced studies at both farm and regional level. The former consist of whole-farm models to estimate impacts of changes in yield arising from global climatic change on cash flow and vulnerability of different farm types (Mooney and Arthur, 1990). Regional production and macro-economic models have also been used to estimate the effects of global climatic change on regional production potential and international trade in agricultural products (Fischer et al., 1995).