Poverty-modulated tree equity shapes health burdens across U.S. cities.

Rapid urbanization concentrates both opportunity and health risk across cities worldwide. Although urban green infrastructure is widely promoted for public health, most evidence examines single outcomes or simple area metrics and rarely tests how socioeconomic context modulates the magnitude and pathways of these benefits. Whether tree-canopy equity delivers stronger returns in areas with the highest poverty remains unresolved. Here, we show that poverty-modulated tree equity shapes health burdens across 497 cities in the United States. Socioeconomic disadvantage is the dominant structural driver of eleven physical and mental health outcomes, yet higher Tree Equity Score is consistently associated with lower prevalence; these protective associations are strongest in high-poverty cities, where greening acts partly by mitigating heat and air-pollution hazards, whereas in low-poverty cities direct restorative pathways predominate. Models explain up to 72.6 percent of the variation in poor mental health, and a five-point rise in the Tree Equity Score corresponds to a 2.7-35 percent lower prevalence of multiple conditions. These findings demonstrate that the health returns of urban greening are context-dependent and require equity-focused strategies stratified by city poverty level.