Spatiotemporal differentiation and driving mechanisms for the synergistic effects of agricultural pollution reduction and carbon emission reduction in the Yangtze River Delta

Sustainable agriculture is often required for the “pollution reduction, carbon reduction, green expansion, and economic growth” against global warming in recent years. This study aims to systematically investigate the spatiotemporal differentiation and driving mechanisms of synergistic effects between agricultural pollution and carbon emission reduction. Taking the Yangtze River Delta as an example, agricultural non-point source pollution and carbon emissions were calculated for each city from 2008 to 2022. A global super-efficiency slack measure model was also combined with the coupling coordination model. A spatiotemporal weighted regression model was introduced to explore the influences of five dimensions (e.g., cultivated land use, socio-economic factors, production, policy, and natural endowment) on the synergistic effects. The results show that: 1) Agricultural non-point source pollution declined from 2008 to 2022, with reduction rates of 20% in Zhejiang and Jiangsu provinces. Anhui province averaged only a 0.34% annual decline. Agricultural carbon emissions shared significant spatiotemporal heterogeneity, with the gradual decrease in Zhejiang and Jiangsu provinces, significant carbon reduction in Shanghai, and a rapid decline in Anhui after peaking in 2014. 2) The mean synergistic effects improved steadily from 0.366 in 2008 to 0.627 in 2022. While most cities remained coordinated, and the number of low-value synergistic effects decreased progressively, indicating a converging trend toward medium-high values. Meanwhile, the polarization was intensified among cities, with a high-east and low-west gradient. High-value areas were concentrated in northern Zhejiang and southern Jiangsu, whereas low-value areas were scattered in central-western Anhui and southern Zhejiang, such as Huainan, Chuzhou, and Quzhou. 3) Crop cultivation structure, cultivation land scale, urbanization, and financial support for agriculture were the key drivers of the synergistic effects, with remarkable spatiotemporal heterogeneity between them. The crop cultivation structure overall played a positive role, especially in southern Zhejiang and northeastern Jiangsu; Its regression coefficients were negative in the central study area, where the negative zone gradually shifted toward northwestern Anhui. The positive impact of cultivation land scale strengthened continuously in western Anhui and northeastern Jiangsu, while the expansion scale was unfavorable for the synergistic effects in southwestern Zhejiang province. Since urbanization exerted an inhibitory effect, a positive driving force of eco-friendly agriculture was observed in southern Zhejiang. Regression coefficients of financial support displayed a west-high and east-low differentiation pattern. In conclusion, the findings can provide a strong reference for the synergistic effects of pollution and carbon emission reduction from an efficiency perspective in sustainable agriculture.