Which trees are best in the fight against air pollution? New framework to help decide which trees are best in the fight against air pollution A study from the University of Surrey has provided a comprehensive guide on which tree species are best for combatting air pollution that originates from our roads – along with suggestions for how to plant these green barriers to get the best results. Air pollution experts from Surrey’s Global Centre for Clean Air Research (GCARE) conducted a wide-ranging literature review of research on the effects of green infrastructure (trees and hedges) on air pollution. The review found that there is ample evidence of green infrastructure’s ability to divert and dilute pollutant plumes or reduce outdoor concentrations of pollutants by direct capture, where some pollutants are deposited on plant surfaces. As part of their critical review the authors noted a lack of resources to help people – including urban planners, landscape architects and gardeners – make informed decisions on which species of vegetation to use and, crucially, what factors to consider when designing a green barrier.To address this gap, they identified 12 influential traits for 61 tree species that make them potentially effective barriers against pollution.