Browsing by Author "Matthew, Olaniran Jonathan"

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    Simulation of the Influence of Climate change on Crop Yield and the effects of Reforestation in Nigeria.
    (Obafemi Awolowo University, 2013) Matthew, Olaniran Jonathan
    This study used a dynamical Regional Climate Model (RegCM3) to simulate the climate of Nigeria for 1999 - 2009, 1981 - 2000 and 2031 - 2050 time periods and the General Large Area Model (GLAM) for the yields of some staple food crops (maize, rice, sorghum, cowpea and groundnut) in the country. This was with a view to investigating the influence of climate change on crop yields and quantifying the effects of future reforestation in the country. The daily climatic data (rainfall, solar radiation, ground surface minimum and maximum temperatures) required to drive GLAM were obtained from the simulation of RegCM3 forced with EH50M global climate model over Nigeria. GLAM was then calibrated for the simulation of yields of the selected food crops in Nigeria. For the GLAM calibration and validation, 11-year (1999 - 2009) climatic and observed yield data were used. The recent past (1981 - 2000; as the baseline) climate and crop yields were then simulated. Similarly, the future (2031 - 2050) climate projections with elevated CO2 under the Intergovernmental Panel on Climate Change A1B scenario were carried out. The GLAM crop model was also used to simulate the adaptive potentials of the choices of some climate change adaptation options (i.e. irrigation farming, adoption of high temperature-tolerant crop varieties and change in planting routine) by peasant farmers. Seven different hypothetical reforestation options were considered for modelling the influence of reforestation on future climate and crop yields in the country. Four of these options assumed random reforestation (i.e. 25%, 50%, 75% and 100%) over the country, while the other three assumed zonal reforestation (i.e. south, middle-belt and north). The results showed that RegCM3 replicated the essential features of Nigerian climate and adequately simulated their seasonal variations (r= 0.74 – 0.95; at p≤ 0.01) over various ecological zones of the country. GLAM gave a realistic simulation of crop yields (1999 - 2009) over Nigeria though with some biases (errors < 36% of the observed yields). The climate model predicted a significant increase (1 - 2oC; p ≤ 0.01) in maximum temperature over the entire country in the future (2031 - 2050). Also, the southern and northern parts of the country were modelled to get wetter (1.5%) and drier (1.7%) respectively in the future. Furthermore, declines in future crop (e.g. maize: 21%, rice: 17%, sorghum: 18%, cowpea: 22%, groundnut: 23% over the Forest zone) yields were predicted over the entire country. However, adoption of some climate change adaptation options reduced (6 - 12%) the negative effects of climate change on crop yields or offset the negative effects and enhanced (2 - 78%) the yields. Reforestations lowered (1 - 2%) temperatures and induced (3 - 12%) rainfall over the reforested areas; but increased (1 - 2%) temperatures and reduced (1 - 2%) rainfall outside the reforested areas. Also, reforestations further increased the negative effects of climate change on crop yields by 1 - 2% over the Forest zone while over the Sahel, the negative effects on the yields were reduced by 1 - 2% or completely offset and improved by 1 - 8%. The study concluded that reforestations had both positive and negative impacts on future climate and crop yields in Nigeria. It improved future crop yields over Nigerian Savannas, but worsened it over the Forest zone.