Analysis of Agroclimatic Zones of Nigeria Under Current and Future Climate Projections for Food System Planning

Agroclimatic zoning classifies agricultural land by the combination of temperature, rainfall, evapotranspiration, and growing season length that govern crop productivity potential, providing a fundamental planning tool for food systems and agricultural policy. This study analyzes the current agroclimatic zones of Nigeria and projects their future configuration under CMIP6 climate scenarios, providing a comprehensive analytical resource for national food system planning. Current agroclimatic zones were delineated using a Thornthwaite-Mather water balance approach applied to gridded climatological data from NiMet's 30-year normals and ERA5 monthly climatology. Future agroclimatic zone configurations were projected using statistically downscaled CMIP6 multi-model ensemble outputs for SSP2-4.5 and SSP5-8.5 scenarios at two time horizons: 2041-2060 and 2061-2080. Results reveal that under SSP2-4.5 by 2041-2060, approximately 14 percent of Nigeria's land area is projected to shift to a drier agroclimatic classification, with the most severe transitions occurring at the Guinea Savanna-Sudan Savanna boundary in Kebbi, Sokoto, and Katsina states. The length of the growing period is projected to shorten by 12 to 25 days in the Sudan Savanna and Sahel zones, while southern rainforest zones may experience lengthening of the growing season with increased heat stress risk. Spatial planning implications for the Green Imperative Project and the National Agricultural Development Fund are discussed. Keywords: agroclimatic zones, CMIP6, food system, growing season, climate projection.