Abstract
The United Nations specifies the need for improving air quality to reduce adverse per capita environmental impacts of cities in Sustainable Development Goal 11. Within this framework, urban trees are widely promoted as a critical intervention for supporting global clean air policies. However, the extent to which they affect air pollution and the associated health burden remains unclear. Here, we quantify the effects of urban trees on PM2.5 concentrations across 125 countries using a generalized linear mixed-effects model and estimate the resulting premature deaths. We find that the impacts of urban trees exhibit strong geographical disparities, reducing annual PM2.5 concentrations in some countries while exacerbating them in others. Specifically, urban trees mitigate annual PM2.5 concentrations by an average of 0.14 µg/m³ in 64% of the analyzed countries, while exacerbating concentrations by an average of 0.13 µg/m³ in the remaining countries. Consequently, urban trees are estimated to prevent approximately 2191 premature deaths annually, while also contributing to 207 additional deaths. These impacts underscore a notable dual effect, indicating that benefits and risks associated with urban trees lack consistent performance across different contexts. Our findings highlight that although urban greening remains a broadly positive strategy for improving air quality and public health, its double-edged effect suggests it should complement, rather than serve as the central strategy for air pollution control.
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We thank all data providers. We gratefully acknowledge financial support from the Key Program of National Natural Science Foundation of China (Grant No. 42530514), the National Key Research and Development Program of China (Grant No. 2022YFF1303102), and the Program of China Scholarship Council (Grant No.202506190137).
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Sun, H., Ni, Y., Kong, F. et al. Dual effect of global urban trees on PM2.5 and associated health burden.
npj Urban Sustain (2026). https://doi.org/10.1038/s42949-026-00415-z
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DOI: https://doi.org/10.1038/s42949-026-00415-z
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