The spatial impact of population semi-urbanization on sulfur dioxide emissions: Empirical evidence from China.

Population semi-urbanization has become a significant feature in the process of urbanization in some countries, especially China. Although the impact of population and urbanization on the ecological environment was thoroughly studied, the role of the semi-urbanized population needs further discussion. This research studies the spatial effect of population semi-urbanization on sulfur dioxide (SO2) emissions through provincial data from China. Multiple spatial weights are used to test the result robustness. Terrain flatness is applied as an instrumental variable to address the endogeneity issue. The mediating and moderating effects explain the impact mechanism of population semi-urbanization. Counterfactual analysis and heterogeneity analysis deepen the research results. The findings are summed up as follows: (1) Population semi-urbanization stably shows an inhibitory effect on the SO2 emissions. (2) Innovation driven is the main mediating factor for population urbanization to reduce SO2. Producer service development strengthens the SO2 reduction effect of population semi-urbanization. (3) Pure urbanization without semi-urbanized population can exacerbate SO2 emissions. (4) The impact of population semi-urbanization is stronger in areas with higher economic levels and income levels, while lower agricultural dependence and infrastructure levels are more conducive to the SO2 reduction effect. The research results can provide a reference for China's registration policy and the immigration policies of countries around the world from an environmental perspective.