Can forest city construction affect urban air quality? The evidence from the Beijing-Tianjin-Hebei urban agglomeration of China

The Beijing-Tianjin-Hebei (BTH) urban agglomeration is the most polluted area of smog in China. The latest studies have been focusing on the influencing factors on the BTH's PM_2.5 concentration in terms of industrial, social, and climatic conditions. However, the role of the urban forest system has not been thoroughly studied in air pollution control. This study focuses on the impact of forest city construction on BTH's PM_2.5 concentration. According to the theoretical framework of the STIRPAT model, we used the spatial Durbin model of bidirectional fixed effect to empirically test the correlation between the BTH's PM_2.5 concentration and the characteristic variables of forest cities. The research results show that improving urban green space, park green space, and investment of urban sanitation and environment facilities can reduce the PM_2.5 concentration in the local and adjacent areas. This study proposes that the construction of forest cities should be further strengthened to alleviate urban air pollution in the BTH's coordinated development and thus improve regional air quality.