Construction of multifunctional composite networks and resilience evaluation under multiple attack scenarios: A case study of the Yangtze river delta

The Yangtze River Delta (YRD), China's most rapidly urbanizing region, faces escalating ecological challenges including urban heat island effects and fragmentation of ecological networks. Existing studies often address ecological connectivity or thermal mitigation in isolation, lacking a comprehensive framework integrating ecological, thermal, and economic functions. This study integrates the gradient source model and circuit theory to optimize a multi-functional composite network linking ecological services, thermal environment diffusion, and economic interactions in the YRD. The result shows: (1)The total lengths of optimized corridors are 3161.98 km (ecological), 3364.83 km (thermal), and 2205.02 km (economic). Ecological corridors show strong continuity, supporting biodiversity and habitat connectivity; thermal corridors aid in urban heat dispersion; and economic corridors emphasize regional accessibility. (2)A multi-level corridor hierarchy reveals that ecological services dominate at the primary level, while thermal and economic functions are more dispersed in secondary and tertiary levels. (3)Under five attack scenarios, network simulations show that random attacks have limited impact, whereas attacks based on betweenness centrality (BC) significantly reduce network efficiency, connectivity, and robustness, fragmenting the largest subgraph. Attacks based on degree centrality (DC) and straight-line closeness (SCL) cause moderate disruption, slightly exceeding that of K-shell-based attacks. (4)Key protected zones totaling 12,662 km2 in northwestern Jiangsu and northeastern Zhejiang are identified as crucial nodes for maintaining functional integration. These findings offer strategic insights into sustainable spatial planning and ecological protection in the region.