Food crop production in Nigeria. II. Potential effects of climate change

Two separate lines of investigation were adapted from the recommendations of the 1994 United States Country Studies Program (USCP). In one approach, arbitrary incremental scenarios were adopted to assess the response of crop yield to changes in the various elements of climate. Using the erosion productivity impact calculator (EPIC) crop model, tests were conducted to demonstrate how crop yield might respond to changes in rainfall, relative humidity (RH), temperature, solar radiation and CO2 concentration. The value of one element was altered incrementally while holding constant the values of the others. In the second approach, potential future changes in the yields of maize, sorghum, millet, rice and cassava were simulated based on a scenario specifying mean conditions for 1961-9190 as a baseline and general circulation model (GCM) projections from this for 3 periods: 2010-2039, 2040-2069 and 2070-2099. The results predicted a possible increase in crop yield during the first half of the 21st century to be followed by a decrease during the second half. Enhanced crop yield was explained by projected increases in rainfall, solar radiation, atmospheric humidity and CO2 concentrations. Lower yields were explained in terms of continued global warming, as a result of which maximum and minimum temperatures approach the limits of tolerance for the modelled crops.