Solving Cities

The most important tool for cutting urban pollution

Posting in Environment

Green walls can decrease urban pollution by as much as 30 percent.

It's no surprise that plants clean up our air, but just how much of a positive impact they can have on urban pollution is now more clear.

New research, which was published this week in the journal Environmental Science and Technology, shows that green walls and other plant infrastructure (as simple as trees and bushes and as complex as green walls) could reduce pollution in urban environments by as much as 30 percent. According to the researchers, green infrastructure -- specifically green walls of grass, climbing ivy, and other plants -- is more than 10 times more effective at reducing pollution than previously thought.

"Urban canyons," where streets are surrounded by tall buildings made of concrete and glass, were the focus of the study. It's in these urban areas where people are exposed to the highest levels of pollution. When researchers used computer models to show the impact of plants in these street canyons on pollution compared to plants in parks or on roofs, green walls were the most effective at removing pollution. Street trees, on the other hand were less effective in street canyons because they trapped pollution at ground level, but were effective on less polluted streets. The researchers also suggest "green billboards" as a way to increase the amount of plants in street canyons.

"Up until now, every initiative around reducing pollution has taken a top-down approach – scrapping old cars, adding catalytic converters to cars, and bringing in the congestion charge – some of which have not had the desired effect," said Rob MacKenzie, a professor at the University of Birmingham and one of the authors of the study, in a news release. "The benefit of green walls is that they clean up the air coming into and staying in the street canyon – planting more of these in a strategic way, could be a relatively easy way to take control of our local pollution problems."

[h/t BBC]

Photo: Flickr/Bill Anderson

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Tyler Falk

Contributing Editor

Tyler Falk freelance journalist based in Washington, D.C. Previously, he was with Smart Growth America and Grist. He holds a degree from Goshen College. Follow him on Twitter. Disclosure