How does agricultural industrial structure upgrading affect agricultural carbon emissions? Threshold effects analysis for China

China continues to emphasize the importance of reducing agricultural carbon emissions and promoting the upgrading of its agricultural industry structure. However, the relationship between the two is rarely examined. This study aims to investigate the impact of upgrading the agricultural industry structure on agricultural carbon emissions. A two-stage instrumental technique and a threshold regression model are used in this study's analysis. The results indicate that agricultural industrial structure upgrading reduces agricultural carbon emissions by a statistically significant amount above the threshold of 0.378. The examination of the underlying mechanism shows agricultural energy efficiency and off-farm work as mediators of the nonlinear relationship between agricultural industrial structure upgrading and agricultural carbon emissions. Only when the agricultural energy efficiency and off-farm work thresholds are surpassed can improving the structure of the agricultural industry minimize agricultural carbon emissions. Analysis of heterogeneity indicates that the threshold for lowering agricultural carbon emissions is greater in northern China, but the potential for reduction is greater.