Unraveling the tourism-urbanization-ES nexus within a human-environment system: spatiotemporal coordination and barrier diagnosis in the Yangtze River Delta, China

The ternary coupling of tourism, urbanization, and ecosystem services (ES) within a tourism-urbanization-based coupled human–environment system (TU–CHES) is critical for sustainability but remains insufficiently examined. This study develops an integrated framework combining Ecosystem Service Value (ESV) quantification, Coupling Coordination Degree (CCD) model, and Obstacle Degree (OD) model to diagnose the spatiotemporal dynamics of coordination and underlying barriers within the TU–CHES in China’s Yangtze River Delta from 2000 to 2020. The results reveal pronounced asynchronous development, where the rapid growth of tourism and urbanization contrasts sharply with the stagnation of ES. Although the overall system coordination improved (mean CCD increasing from 0.389 to 0.436), the progress is highly spatially uneven. Shanghai demonstrates an ecological overload, while Jiangsu experiences coordination regression, underscoring persistent spatial mismatches. Further analysis identifies three deep-seated institutional barriers: the scale–status paradox of tourism, dual deficits in cultural and environmental governance during urbanization, and the tension between landscape commodification and ecological regeneration. To address these challenges, this study proposes transboundary ecological compensation, recalibrating tourism development strategies, and differentiated landscape management. The integrated ESV–CCD–OD framework provides a transferable diagnostic tool for analyzing sustainability constraints in tourism-driven urban agglomerations.