Multiscale Ecosystem Services Supply–Demand Assessment in Ghana Using Improved Population Representation

Ecosystem service supply–demand (ESSD) assessments depend heavily on the spatial representation of human demand. However, coarse population datasets may overlook local variations, thereby affecting the identification of supply–demand imbalances. This study develops a multiscale ESSD assessment framework for Ghana that integrates improved population representation and ecosystem service indicators. Census-based population data for 2021 were downscaled to 0.05°, 0.01° and 0.005° resolutions. When aggregated to the district level and compared with the corresponding census totals, the SRF estimates demonstrate lower %RMSE than LandScan and WorldPop, with relative reductions of 21.02% and more than 59%, respectively. Spatial consistency assessment further showed a strong positive association between population density and built-up land proportion. Four ecosystem services, including food supply, water yield, carbon sequestration, and soil conservation, were evaluated using supply-demand ratios, spatial clustering analysis, and SHAP-based interpretation across multiple spatial scales. The results demonstrate that finer population representation captures more detailed ESSD heterogeneity, especially in urban and peri-urban areas. Water-yield imbalance exhibited marked spatial heterogeneity across Ghana, whereas food and carbon imbalances were most evident in coastal and highly urbanized regions. These findings highlight the importance of population spatialization in multiscale ESSD assessment and provide insights into spatially targeted land management in rapidly urbanizing regions.