An Original Framework for Quantifying Ecosystem Services from Nigerian Agricultural Soils: From Soil Function to Service Valuation

This dissertation develops an original framework for quantifying and valuing ecosystem services provided by Nigerian agricultural soils, bridging the conceptual gap between soil function measurement and ecosystem service economic valuation in a manner applicable to Nigerian policy and investment decisions. Soil ecosystem services including food production support, water purification, carbon sequestration, flood buffering, and biodiversity support are fundamental to Nigeria's agricultural economy and environmental security, yet they are systematically omitted from national accounts and investment decisions because no quantification framework adapted to Nigerian soil and socioeconomic conditions exists. This study employs a three-tier methodology: systematic quantification of soil function indicators for 18 key soil ecosystem services across 300 sampling sites in all six geopolitical zones; development of soil function to service supply transfer functions using empirical relationships between soil properties and measurable service proxies; and economic valuation using a combination of market pricing, avoided cost, willingness-to-pay, and benefit transfer methods. Structural equation modelling tests the causal pathways between management interventions, soil function improvement, and service supply. The dissertation proposes the Nigerian Soil Ecosystem Service Valuation Framework (NSEVF) as an original contribution, providing standardised methods for incorporating soil health into environmental impact assessments, investment appraisals, and green national accounting for Nigeria. Application of the NSEVF to five case study landscapes reveals that soil degradation costs Nigeria an estimated 1.2 to 2.4 billion USD annually in lost ecosystem service value across the analysed zones. Keywords: soil ecosystem services, valuation framework, soil function, Nigeria, green accounting.