This paper quantifies the impact of rural–urban migration on agricultural fires, a major source of air pollution in China. Using satellite records and census data, we exploit an exogenous trade shock that raised manufacturing labor demand in destination prefec-tures, drawing workers from origin counties through established migration networks. A one-percentage-point increase in rural labor emigration in 2010 led to a 5% rise in agricultural fires from 2011 to 2017. The effect stems from reduced agricultural labor, which incentivizes fire use as a labor-saving clearing method. Consistent with this mech-anism, we find no effect from non-agricultural emigration or from migration to nearby areas where return farming remains feasible, with the strongest impact during harvest seasons. Institutional reforms, particularly land titling programs, significantly mitigate the problem by enhancing tenure security, enabling farmland reallocation, and reducing reliance on fire—proving more effective than nationwide administrative bans.