Actual supply-demand of the urban green space in a populous and highly developed city: Evidence based on mobile signal data in Guangzhou

The rational assessment of the urban green space supply-demand relationship is crucial aspect to achieving Sustainable Development Goals. However, previous research predominantly focused on evaluative and indirect exposure calculations for the lack of precise geographic boundaries for urban green space and their refined visitation data. This has led to an evaluation of the supply-demand relationship that may deviate from the actual condition. In this study, the precise geographic boundaries, functional characteristics, and scale information of planned urban green space in Guangzhou were utilized. Then, the supply-demand relationship of urban green space was assessed using mobile signal data to capture real-time exposure. The results show that 20.8% of the urban green space in Guangzhou suffers from undersupply, which is especially pronounced in the central urban areas. The imbalance is more pronounced on weekends compared to weekdays, with 10.6% higher undersupply rates. In addition, the Gini for the monthly average of green space exposure is 0.71, indicating a highly unequal of green space exposure in Guangzhou. The real exposure inequality of urban green space in the central urban area is better than in the peripheral area. In particular, small-scale urban green space documents a more severe imbalance, and the exposure is significantly correlated with the scale of urban green space. Based on these findings, this study provides scientific recommendations for urban green space supply planning including scale, spatial arrangement, and indicator optimization.