Salient air pollution mobilizes bottom-up green engagement: Evidence from the world's largest green mobile program.

Air pollution imposes large health and economic costs worldwide, yet most mitigation efforts still rely primarily on top-down regulation of major emitters. We examine whether salient deterioration in local air quality mobilizes bottom-up engagement with a green digital program. Using user-month panel data on 200,000 users of Ant Forest-the world's largest green mobile program-across 331 Chinese cities from 2019 to 2020, we show that the same individuals respond to severe local pollution by generating more green energy through eligible low-carbon activities, engaging more intensively and more frequently with the program to collect the resulting credits, and redeeming more credits for collaborative tree planting in the following month. The responses are dose-responsive-larger under "Hazardous" (AQI ≥ 300) than "Very Unhealthy" (AQI ≥ 200) conditions-and representative survey data show that pollution exposure raises stated environmental concern. Our findings indicate that digital green programs can help translate heightened environmental concern into measurable green engagement and downstream environmental contributions, complementing top-down regulation.