slight warming (Figure 4-25) because they are currently grown under conditions close to maximum temperature tolerances. Adaptation gives tropical regions a buffer of ap­proximately 3°C of warming before yields of wheat, maize and rice decline below current levels.
     Two regions that are likely to experience large nega­tive impacts of climate change on agricultural production are Asia and Africa. Studies indicate that rice production across Asia could decline by nearly 4% over this century. In India, a 2°C increase in mean air temperature could de­crease rice yield by about 0.75 tonnes ha-1 and cause a de­cline in rain fed rice in China by 5 to 12%. Sub-Saharan Africa could lose a substantial amount of cropland due to climate change-induced land degradation. Based on results from one climate model (HadCM3), as many as 40 food-insecure countries of sub-Saharan Africa may lose an aver­age of 10 to 20% of their cereal-production potential due to climate change. Whether such declines are problematic depends on possibilities for trade and responses from ag­ronomic research. However, some studies suggest that the impacts of climate change within a region are likely to be extremely heterogeneous, depending on local conditions. Several crop and livestock systems in sub-Saharan Africa that are highly vulnerable may experience severe climate change (Thornton et al., 2006). These include the more mar-

ginal mixed (crop-livestock) and pastoral systems in parts of the Sahel, East Africa, and southern Africa. In some areas, growing seasons may contract, and crop and forage yields may decline substantially as a result (Jones and Thornton, 2003). Vulnerable households in such places will need to adapt considerably if food security and livelihoods are to be preserved or enhanced.
     While most studies still focus on changes in means, in fact changes in variability and extreme weather events may be even more important for agriculture than the changes in means. For instance, changing the frequency of dry years may seriously affect agriculture in certain areas. Climate change will not be a major challenge to agri­cultural production systems in temperate regions until well into this century. In the tropics, especially Asia and Africa, however, even with adaptation, food (especially grain) pro­duction may decline with only modest amounts of climate change. Modeling studies also suggest that real food prices will reverse their long-term decline at about 3°C of warm­ing, resulting in increasing prices thereafter.

4AAA Climate change mitigation and agriculture
According to several assessments, agriculture and forest­ry can play a significant role in mitigation policies (FAO, 2006d; IPCC, 2007c) as it is also a major source of green-