Climate change impacts on cowpea productivity in Nigeria
If a climate signal could be detected at state or regional level, it would be useful to policy planners, agricultural authority and farmers to prepare for climate change. This study, therefore, employed a statistical model to investigate the relationship between the yield of cowpea and temperature (in centigrade) and precipitation (in millimeters) for the period 1961 – 2006 at state levels in Nigeria. The analyses were based on all the twenty major cowpea producing states for the main period 1961 -2006. Data for
annual yield of cowpea for all the time period were collected from the Nigeria Bureau of Statistics (N.B.S). Data on the two important climate variables required for crop growth - temperature and precipitation - at state in Nigeria were obtained from the Nigerian Metrological Agency. The response of cowpea yield to climate change varied from one geographical location to the other. The results indicated negative and significant relationship between cowpea yield and temperature in six of the twenty states producing cowpea in the country. Five of the six states are in the northern part while the remaining one is in the south. The results of the relationship between the yield and precipitation were similar to those of temperature in the northern states, except Sokoto. There was a negative correlation between rainfall and cowpea yield in Adamawa, Bauchi, Kaduna, Katsina, Kwara, Niger Plateau and Yobe. On the contrary, increase in precipitation will lead to increase in yield in the southern part except Kwara. The time trend is positive and significant in all the cases except in Adamawa, Bauchi and Jigawa where time trend was non significant though
positive..These results also show that as the years pass by and climate factors run contrary to agricultural productivities, cowpea farmers were adopting new measures to cope with the negative effect of climate change. Through adaptation, the negative effects of climate change on cowpea yield could be reduced and the positive influences enhanced. Examples of potential adaptive measures include the introduction of drought or heat resistant varieties, early sowing, mixed cropping, alteration of the tillage system and utilization of land that has been considered too marginal for agricultural cultivation.
Key words: Climate change, statistical modeling, Nigeria