Ecological sensitivity and sustainable spatial planning in a highly urbanized plain: An AHP-GIS and geodetector approach in the Yangtze River Delta Plain.

Rapid urbanization in plains exacerbates ecological pressures, while most ecological sensitivity (ES) research focuses on mountains, offering limited guidance for highly urbanized plains. This study assesses ES in the Yangtze River Delta Ecological Green Integrated Development Demonstration Zone (YRD EGI-DDZ) and its planning implications. Ten indicators, covering four criteria, geography, hydrology, natural resource, and human interference were integrated using Analytic Hierarchy Process (AHP) with Geographic Information System (GIS). Geodetector quantified drivers of ES spatial variation, and 2018-2020 land use data revealed recent development and fragmentation. Results show over 70% of the area under medium to extremely highly sensitivity, with high or extreme high zones clustered along Dianshan Lake, Yuandang, East Taihu, and contiguous ecological land. Low sensitivity mainly corresponds to urban land. Key drivers include land use, nighttime lights, population density, and water proximity, while elevation and slope contribute marginally. New construction land expands mainly along urban fringes and transport corridors, inserting low sensitivity strips into medium sensitivity belts and fragmenting high sensitivity cores. These findings inform a sensitivity-based zoning and corridor control framework, refining existing plans and supporting sustainable spatial development in similar plains.