- Other than Carbon Dioxide removal, which is treated in a separate article, trees have a profound effect on air quality.
- One acre of trees generates enough oxygen each day for 18 people.
- Trees absorb gaseous pollutants into their leaves and trap and filter particulates on and through their leaves, stems, and twigs. Pollutants partially controlled by trees include nitrogen oxides, sulfur dioxides, carbon monoxide, carbon dioxide (required for normal tree function), ozone, and small particulates less than 10 microns in size.
- Trees lower local air temperatures (reduce urban “heat island” effects) by transpiring water, shading surfaces and reducing cooling costs, energy use and the resulting pollution.
- In 1994, trees in San Diego removed an estimated 1,260 metric tons of air pollution at an estimated value to society of $7.0 million (Air pollution removal by urban trees and shrubs in the United States, David J. Nowak, Daniel E. Crane, Jack C. Stevens, 1994).
The American Society of Landscape Architects has created an animated video that visually presents the benefits of urban forest for creating cleaner and cooler air.