Urban tree canopy fragmentation and child mortality in low- and middle-income countries.

Exposure to urban green spaces is associated with lower risks of several leading causes of under-5 mortality (U5M). While urban development improves infrastructure, healthcare access, and socioeconomic conditions, rapid urbanization in low- and middle-income countries (LMICs) has also accelerated the loss and fragmentation of green spaces. Such fragmentation may weaken ecosystem services critical for child health and increase exposure to vector-borne infections, yet its implications for U5M remain poorly understood and must be weighed against the benefits of urbanization. Here, we quantified associations between urban tree canopy cover and canopy aggregation with all-cause U5M using individual-level longitudinal mortality data between 2000 and 2019 from 57 LMICs, and identified priority areas for expanding canopy cover and improving canopy aggregation across 98 LMICs using counterfactual scenario analyses. The association between canopy cover and U5M was nonlinear, with risk declining steeply at low-to-intermediate levels of canopy cover. At a given level of canopy cover, every 1% increase in tree-to-tree adjacency was associated with a 0.17% reduction in mortality risk (hazard ratio: 0.9983, 95% CI: 0.9972 to 0.9995). The largest contiguous high-priority areas were concentrated in the West Sudanian Savanna, the eastern Punjab region of Pakistan, and the Ganges-Brahmaputra Delta in Bangladesh, where high U5M burdens align with substantial potential to improve tree canopy. This study establishes a robust association between tree canopy characteristics and U5M across LMICs. We identify canopy cover and fragmentation as potentially modifiable risk factors, highlighting important implications of urban greening design for delivering cobenefits for child health and climate mitigation.