Spatiotemporal patterns and inequity of urban green space accessibility and its relationship with urban spatial expansion in China during rapid urbanization period

Equitable access to urban green spaces (UGS) is an important component of social justice and can be quantified using indices such as urban green space accessibility (UGSA). However, the spatiotemporal patterns and inequity of UGSA among cities with different developments during rapid urbanization are unclear, especially lack evidence at a macroscopic national scale during rapid urbanization. Therefore, we evaluated the UGSA in 366 cities of China during 1990–2015 by the Gaussian-based two-step floating catchment area method (Gaussian-based 2SFCA). Then, the inequity pattern of UGSA among cities with different economic developments was analyzed by the concentration curve and concentration index. Finally, the relationship between UGSA and urban spatial expansion was explored quantitatively by the spatial econometric model. The results showed that: (1) The overall UGSA in China declined significantly by nearly 57.23% during 1990–2015. From the regional perspective, the UGSA in the southeastern region was always lower than that in the northwestern region, the Eastern zone presented a downward trend. From the perspective of different sizes cities, the UGSA of the megacities kept decreasing during 1990–2015, while UGSA of the large, medium, and small cities had turned to increase since 2010. (2) During rapid urbanization, the equity of UGSA among the cities gradually improved, while the cities with low economic developments tended to have higher UGSA. (3) Urban spatial expansion led to the decrease of UGSA during 1990–2015, while the impact had spatiotemporal heterogeneity, and UGSA had a positive spatial spillover effect. Our research provides a comparative baseline for the improvement of UGSA from a macroscopic perspective for China's urbanization policy in the future and novel insights into the green justice issue. The results can be compared with the development of UGS in other countries at different urbanization stages to promote UGS design and policy.