Vulnerability of African maize yield to climate change and variability during 1961-2010

Because of the necessity of feeding growing populations, there is a critical need to assess the variation and vulnerability of crop yields to potential climate change. Databases of maize yields and climate variables in the maize growing seasons were used to assess the vulnerability of African maize yields to climate change and variability with different levels of management at country scale between 1961 and 2010. The ratios of time-series trends or standard deviations of detrended yield deviation and climate variables including temperature (T-mean), precipitation (P) and standardized precipitation evapotranspiration index (SPEI) were used to analyze the vulnerability of maize yields to climate change and variability for each country in Africa. Most countries, where soil fertility had been declining owing to low levels of fertilizer use over many years and limited water resources, had decreasing maize yields. The negative impacts of increasing temperature and decreasing precipitation and SPEI on maize yields progressively increased at the whole continent scale over the time period studied. During the maize growing seasons 1961-2010, each 1 degrees C of T-mean increase resulted in yield losses of over 10% in eight countries and 5-10% in 10 countries, but yields increased by more than 5% in four relatively cool countries. Decreases of 10% average P resulted in more than 5% decreases in yields in 20 countries and each decrease of 0.5 SPEI resulted in over 30% losses of maize yields in 32 countries. Greater T-mean or P or SPEI variability in Africa may also bring about greater fluctuations in yield. In addition, countries with better management, which would be expected to have better yields, may be more vulnerable to yield losses due to adverse physical conditions. Better irrigation and fertilizer application will be important to sustain higher yields in the future, as will the development of maize varieties with greater heat and drought tolerance.