Watershed-targeted environmental governance and pollution reduction: evidence from the Yangtze river economic belt

Difference-in-differences analysis showing that the 2018 Guiding Opinions reduced ammonia nitrogen emissions by 16% in Yangtze River Economic Belt provinces, transmitted through livestock farm consolidation. Diffuse pollution from agricultural and rural activities poses persistent challenges for water quality management in large river basins with fragmented administrative governance. This study evaluates the environmental effects of the Guiding Opinions on Accelerating the Governance of Agricultural Non-Point Source Pollution in the Yangtze River Economic Belt (YREB), a basin-targeted, multi-agency governance framework implemented in China in 2018. Using provincial panel data from 2012 to 2021 and a difference-in-differences approach, the study finds that the policy is associated with a statistically significant reduction in ammonia nitrogen emissions, with an estimated coefficient of 0.178 (10% level), implying approximately 16% reduction relative to the control group. The effect emerges one year after policy issuance, consistent with gradual implementation. Mechanism analysis reveals a conditional effectiveness pattern: detectable reductions occur through the livestock consolidation channel, where compliance is administratively observable, but not through agricultural input channels, where diffuse smallholder behaviour is hard to monitor. These results suggest that the effectiveness of coordinated multi-agency arrangements is bounded by the enforcement tractability of the instruments being coordinated.