Simulating the Impacts of Climate Change on Water and Crop Productivity in Ogun-Osun River Basin, Nigeria

Abstract

African countries such as Nigeria are anticipated to be more susceptible to the impacts of climate change due to the large dependence on rainfed agriculture. Also, there are several uncertainties in the responses of rainfed crop production to climate change. In this regard, the impacts of climate change on crop water requirements (CWR), irrigation water requirements (IWR), yields and crop water productivity (CWP) of rainfed maize and soybeans in Ogun-Osun River Basin, Nigeria were evaluated for the baseline period (1986 – 2015) and future period (2021 – 2099) under RCP 4.5 and RCP 8.5 scenarios. Future climate projections of HadGEM2-ES downscaled by RCA4 were used in simulating future scenarios. The results show that for the baseline period, maize CWR and IWR have a slightly decreasing trend, but soybeans CWR and IWR are increasing significantly. Though, no significant changes in maize yield but the yield trend of soybeans is increasing and CWP is increasing for both crops. For the future period, the CWR is largely dependent on the rainfall pattern. Maize IWR will likely increase significantly up to 140% in some periods while soybeans IWR is projected to continually decline up to 80 % by 2099. Maize yield will likely decline under both scenarios up to 12% while climate change has positive effects on soybeans yield which will increase up to 40% under RCP 8.5. Meanwhile, based on the baseline period, supplemental irrigation shows a promising effect on crop yields and can increase maize and soybeans yields up to about 10% and 35% respectively. Also, in the future scenarios, it can increase crop yields expect in the late century. The results of this study certainly offer useful information on suitable adaption measures which could be implemented by stakeholders and policymakers to counterbalance the negative effects of climate change on crop production in Nigeria.