The spatial spillover effect and impact paths of agricultural industry agglomeration on agricultural non-point source pollution: A case study in Yangtze River Delta, China

The rapid development of Chinese agriculture has brought about serious agricultural non-point source pollution (ANPSP), and the reduction of non-point source pollution is of great practical importance to realize the green transformation of agriculture, the ecological livability of the countryside and the well-being of farmers. Agriculture industrial agglomeration is widespread throughout the world, and it is generally accepted that there are positive economic effects. However, there is still a debate on whether positive or negative externalities dominate the environmental effects of agriculture industrial agglomeration. Therefore, it is of theoretical significance to correctly identify the nonlinear relationship and spatial spillover effects between agriculture industrial agglomeration and ANPSP. As a region with the rapid development of agricultural intensification in China, the environmental effect of agricultural agglomeration in the Yangtze River Delta is more complex compared with other industries, and It has strong research value to realize the coordinated development of agricultural industry clustering and green agriculture. Based on panel data of 37 cities in the Yangtze River Delta from 2000 to 2019, this paper uses the inventory analysis method to measure the agricultural non-point source pollution (ANPSP) of each city. Then, for the law of spatial evolution of ANPSP, the Spatial Durbin Model (SDM) was developed to analyze the specific impact of agricultural industrial agglomeration on ANPSP. The results show that: (1) the ANPSP of the Yangtze River Delta had a downward trend during 2000–2019, with high-high agglomeration and low-low agglomeration characteristics. (2) The effect of agricultural industrial agglomeration on ANPSP showed an inverted U-shape, which was consistent with the EKC curve. However, after considering the spatial spillover effect, it shifted to a U-shape. (3) Economic, structural and technological effects are the main driving effects for the mitigation of ANPSP, with concentration effects increasing pollution. Therefore, in the future, the moderate-scale business should be encouraged to develop, optimize and adjust the agricultural industrial structure, stimulate technological progress and innovation, enhance the spatial spillover capacity of technological and structural effects, and improve the capacity of nonpoint source pollution management.