Urban-rural difference and scale effect of ecosystem services of blue-green infrastructure.

Blue-green infrastructure (BGI) constitutes the mainstay of urban ecological infrastructure and is a vital element in shaping urban ecological security patterns. Current research on urban BGI primarily focuses on spatio-temporal variations, driving mechanisms, connectivity, and planning management. Less attention has been paid to the spatio-temporal dynamics, coordination, and trade-off mechanisms of BGI ecosystem services (ES) under the background of rapid urbanization. We explored the spatio-temporal variations, urban-rural disparities, and trade-off and synergy effects across different scales of six ES types provided by BGI (climate regulation, air purification, flood regulation and storage, carbon sequestration, landscape culture, and habitat providing) in Wuhan from 1980 to 2020 based on the InVEST model, Getis-Ord Gi* spatial hotspot analysis, and spatial correlation analysis. The results showed that the ES provided by BGI generally exhibited a spatial distribution pattern of low levels in the central urban area and high levels in the periphery, with large areas of cold spots or insignificant regions. There were significant differences in the contribution rates of BGI to different ES, with more contribution from blue infrastructure and less from green infrastructure. The urban-rural gradient impacted fluctuations in ES, with decreasing amplitude as the distance from the city center increased. Furthermore, there were scale effects for trade-offs and synergies among ES. Trade-offs and synergies among ES coexisted at the watershed unit scale, whereas a synergistic relationship prevailed at the township and administrative district scales. Our results could offer valuable insights for the coordinated optimization and hierarchical, categorized, and zoned management of BGI's ES functions amidst urbanization.