Systems Dynamics Modelling of Soil Organic Carbon Under Climate Change and Farming System Scenarios in Nigeria to 2050

This study develops a systems dynamics model of soil organic carbon dynamics under alternative climate change and farming system scenarios in Nigeria, projecting SOC trajectories to 2050 and identifying management interventions that can reverse degradation trends. Soil organic carbon is both a critical determinant of agricultural productivity and a significant component of Nigeria's terrestrial carbon balance, yet its future trajectory under combined climate change and farming system evolution has not been systematically modelled at national scale. This study integrates the CENTURY soil organic matter model with IPCC RCP climate scenarios, Nigeria population and agricultural land use projections, and farming system transition scenarios developed through participatory expert elicitation. Model parameterisation uses an original database of 1,240 soil carbon measurements from across Nigeria compiled through systematic literature review and original data collection. Scenario analysis covers 12 combinations of climate pathway (RCP 2.6, 4.5, 8.5) and farming system transformation (business as usual, moderate agroforestry expansion, radical conservation agriculture transition). Model outputs are validated against observed SOC change data from long-term experiments. Findings reveal that under business-as-usual farming and RCP 8.5, Nigeria loses an additional 18 percent of current agricultural soil organic carbon stocks by 2050. Under radical conservation agriculture and agroforestry expansion combined with RCP 2.6 mitigation, SOC stocks can be stabilised and modestly increased. The study contributes an original national-scale SOC systems model and recommends a national soil carbon monitoring network to track actual SOC change against the modelled trajectories.

Keywords: soil organic carbon, systems dynamics modelling, climate change scenarios, Nigeria 2050, conservation agriculture.