Spatial Heterogeneity, Scale Sensitivity, and Methodological Innovation in Ecosystem Services Assessment for Nigerian Savanna Landscapes

Ecosystem services assessments in tropical African savanna landscapes are methodologically challenged by high spatial heterogeneity in vegetation cover and soil properties, scale-sensitivity of service estimates, and the absence of locally-calibrated biophysical and valuation parameters. This doctoral research addresses these challenges through methodological innovation in ecosystem services assessment applied to Nigerian Guinea savanna landscapes spanning Niger, Kwara, and Oyo states. The research develops and tests new approaches to three critical methodological challenges: calibration of carbon and water regulation service estimates to local biophysical conditions using a novel field campaign at 120 plots combined with satellite-based spatial extension; assessment of scale effects through multi-resolution comparison of service estimate outputs from plot, catchment, and landscape scales; and co-production of culturally appropriate cultural ecosystem service indicators with local communities through participatory methods. The methodological innovations are applied to produce the first rigorous ecosystem services assessment covering 4.2 million hectares of Guinea savanna landscape in the study states. Spatial heterogeneity analysis reveals that standard benefit transfer approaches introduce systematic biases of 35 to 62 percent in carbon and water regulation estimates compared to locally calibrated values, with direction of bias varying by ecosystem condition. Scale sensitivity analysis identifies minimum appropriate mapping units for different service types. Cultural ecosystem service co-production reveals services not captured in standard typologies, including spiritual values of specific tree species. Methodological contributions are documented as transferable protocols for other Nigerian and West African savanna ecosystem services assessments. Keywords: ecosystem services assessment, spatial heterogeneity, savanna landscapes, methodological innovation, Nigeria.