Climate change and crop yields in Zambia: historical effects and future projections

Rainfed farming systems that are prevalent in sub-Saharan Africa are prone to climate change. Most studies have only estimated the impacts of climate change on agricultural productivity at a regional or national level. This overlooks localized effects at the subnational level, especially within defined agro-ecological regions. Using 30 years (1981–2011) of crop yield and weather data in Zambia, we apply the Just and Pope framework to determine how rainfall and temperature affect yield and yield variability of beans and maize at the national and agro-ecological region levels. At the national level, we find significant negative effect of a rise in temperature on bean and maize yield, while rainfall increases have a positive effect on bean and maize yields. These results differ by agro-ecological region. Rainfall has a positive and significant effect on maize yield in the low rainfall regions I and II, but it has a negative effect on maize yield in the high-rainfall region III and no significant effect on bean yield. Temperature has varied effects by regions and crops. Predicted impacts using HadGEM-ES2 global circulation model show that major yield decreases (25% for maize and 34% for beans) by 2050 will be in region II and will be driven mainly by temperature increase offsetting the positive gains from rainfall increase. The model predominantly overpredicts bean yield and under predicts maize yields. These results call for agro-ecological region-specific adaptation strategies and inventive agricultural policy interventions which are more robust to climate change.