Developing multiscale landscape planning to mitigate ecological risks: A case study in Nanjing metropolitan area, China

Rapid urbanization has led to significant changes in ecosystem services (ESs) and thus increased ecological risks. Understating how ESs respond to land use/land cover (LULC) patterns is critical for identifying and controlling ecological risks. However, little is known about the ES patterns, interactions, and drivers at different urban hierarchical scales, posing great challenges for multiscale landscape planning. This study evaluated changes in multiple ESs and identified ecological risks using the Integrated Valuation of Ecosystem Services and Trade-offs model in the Nanjing metropolitan area at the main urban, city, and metropolitan scales during 2000-2020. Then, ES interactions and drivers at different urban hierarchical scales were explored using Spearman's correlation analysis and the GeoDetector. By integrating the ES information above, a new multiscale landscape planning framework was proposed to mitigate ecological risks at different urban hierarchical scales. The results showed that most ESs have declined due to rapid urbanization. The ecological risks decreased with increasing spatial scale. The ES trade-offs/synergies at the small spatial scale may change at a larger spatial scale. Landscape composition was the dominant driver of ESs at the main urban scale, and the influence of natural factors strengthened with an increasing spatial scale. The construction of blue-green infrastructure is an effective way to mitigate ecological risk, but the effect is scale-dependent. Different urban hierarchical scales may face different ecological risks, and targeted landscape planning should be designed for different urban scales. The multi-scale landscape planning framework proposed in this study helps to identify the most effective landscape planning measures at different urban hierarchical scales. More attention should be paid to landscape configuration at small scales and ecological restoration at large scales. This study provides a technical framework to guide sustainable landscape planning and build resilient cities.