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Do trees reduce air pollution levels? © Getty Images

Do trees reduce air pollution levels?

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With half a football field of forest destroyed every second, we need to understand the impact this will have on the quality of our air.

Asked by: Roger Lenton, Salisbury


The relationship between trees and air pollution is a complicated one. Particulate matter suspended in polluted air tends to settle onto leaves, and certain gases including nitrous dioxide (NO₂) are absorbed by leaves’ stomata, filtering the air and reducing pollution levels slightly.

But trees and other vegetation also restrict airflow in their immediate vicinity, preventing pollution from being diluted by currents of cleaner air. In particular, tall trees with thick canopies planted alongside busy roads can act like a roof, trapping pockets of polluted air at ground level. To reliably improve air quality, city planners need to give careful consideration to how trees are placed.

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