Non-monotonic effects and spatial spillovers of urban green space on chronic infectious disease dynamics in China

As global public health faces unprecedented challenges, Urban Green Space (UGS) is increasingly recognized as a vital instrument for health intervention. However, its efficacy in mitigating infectious diseases remains conceptually contested. Drawing on longitudinal data from 300 Chinese prefecture-level cities (2003–2023), this study employs Spatial Durbin Models (SDM) and threshold regression to unravel the complex spatio-temporal trade-offs between UGS and chronic infectious diseases. Focusing on the mitigation of chronic infectious diseases, our findings challenge linear paradigms by unveiling a non-monotonic “risk-to-resilience” transition. In the nascent stages of greening, UGS expansion may paradoxically create a “pathogenic window” elevating transmission risk through intensified human-wildlife-environment interactions. However, once UGS coverage surpasses a critical tipping point, it serves as a potent ecological shield, significantly curbing the spread and latency of chronic infectious diseases. This suppression is achieved through microclimate stabilization, bio-filtration, and the enhancement of community salutogenesis. Furthermore, our analysis reveals robust positive spatial externalities, demonstrating that protection against chronic infections propagates across administrative borders via ecological corridors. This study identifies a pivotal scale effect in green governance, positioning UGS as a long-term strategic asset for demographic health. Our results advocate for a transition from localized planting to trans-regional collaborative green infrastructure networks, providing crucial theoretical scaffolding for the Healthy China 2030 initiative and the management of chronic infectious risks.