Event-driven changes in ecosystem service supply-demand balance and flows in a Winter Olympic host region

Mega-events such as the Olympic Games can drive profound socio-environmental transformations in host regions, but their impacts on ecosystem service supply-demand dynamics and service flows remain poorly understood. This study assesses the spatiotemporal dynamics of four key ecosystem services in Chongli District, China (Beijing, 2022 Winter Olympics venue area), covering the preparation, event, and post-Olympics phases. Results show that the supply-demand ratio for water yield service significantly declined during the event period, followed by gradual recovery in the post-Olympic phase. Conversely, soil conservation and habitat quality services maintain a stable surplus overall. Spatially, the Winter Olympic and residential areas exhibit high demand for water yield and carbon sequestration services, with an increasing trend of supply-demand imbalance. Service flow analysis further reveals that carbon sequestration and habitat quality services primarily transfer from areas with a high supply-demand ratio to regions of intensive human activity, with the Winter Olympic area being the main recipient and showing an increasing service flow intensity. Socioeconomic factors, including population density, nighttime light, and built-up percentage, tend to undermine the supply-demand balance, with this inhibitory impact being especially pronounced within the Winter Olympic area. Moreover, threshold analysis revealed nonlinear driver effects on ecosystem service supply-demand balance. Nighttime light and built-up expansion mainly weakened the balance of water yield and carbon sequestration services, whereas precipitation enhanced water yield balance after crossing a critical level, and increasing population pressure further reduced habitat quality balance. This study supports actionable management, including flow-informed zoning, threshold-based development caps and compensation schemes to maintain water security, carbon sinks and habitat conservation in mega-event host regions.