Pollution Removal

Pollution removal by urban trees in the US is estimated at 822,000 tons per year ($4.7 billion value for removal of ozone, nitrogen dioxide, sulfur dioxide and particulate matter less than 2.5 micrometers), or the equivalent carbon dioxide emissions from 138,510 cars.Nowak, D.J., Greenfield E., J.C. (2018). US Urban Forest Statistics, Values, and Projections. Journal of Forestry, 116(2), p. 164-177.

Vegetation Barriers

Dense barriers of vegetation along roadways increase vertical mixing and concentrations of pollution on the road and generally reduces ground level pollution directly behind barriers relative to a clearing with no barrier.Baldauf, RW., L. Jackson, G. Hagler, et al. (2011). The role of vegetation in mitigating air quality impacts from traffic emissions. Air and Waste Management Associations Magazine for Environmental Managers, January, p. 30-33.

Volatile Organic Compounds

While the emission of biogenic volatile organic compounds (BVOCs) from trees can increase ozone, other beneficial effects of trees tend to reduce ozone, making urban tree canopy cover a viable strategy to improve air quality and help meet clean air standards. BVOCs are highly species dependent.“Urban Air Quality Briefing.” National Association of State Foresters. NASF. 30 Mar. 2017.