Spatial drivers of ecosystem services supply-demand balances in the Nanjing metropolitan area, China

Ecosystem services (ESs) are the foundation of human well-being. Previous studies have paid limited attention to the interactions among several factors that influence the balance of ESs supply and demand at the grid scale. This study focused on four ESs-water yield (WY), grain yield (GY), carbon storage (CS), and recreational services (RS)-and examined their supply and demand in the Nanjing Metropolitan Area (NMA) in 2000, 2010, and 2020 at the pixel level. Our primary objective was to pinpoint regions characterised by imbalances in ESs supply and demand. In addition, we aimed to explore the interactions among the key elements that contribute to these imbalances. The Geodetector model (GD) was employed to elucidate the 14 distinct primary driving factors influencing the ESs supply-demand balance and their interactions. Our results showed that imbalances in WY and CS supply-demand were predominantly identified in the northern and southern regions of the Yangtze River Basin and certain urban centres. Imbalances in GY were occasionally found in the peripheral areas of cities. The spatial patterns of RS supply-demand imbalances resembled population patterns. The interaction between annual runoff depth and the proportion of built-up land (PB) had the highest explanatory power for changes in the WY supply-demand balance at 54%. The interaction between population density (POP) and the proportion of cultivated land (PC) had the highest explanatory power for the GY supply-demand balance at 29%. The interaction between the proportion of forest land (PF) and average annual ground temperature had the highest explanatory power for the CS supply-demand balance at 67%. The combined effect of PB and Net primary productivity had the highest explanatory power for the RS supply-demand balance at 41%. Overall, this study demonstrated the spatial heterogeneity of ESs at a finer scale than at the county level. This is important for the effective conservation and sound management of ESs. These findings provide decision-makers with insights into regulating regional ecosystem factors and improving local ecological environments based on local conditions.