Trees in Cities: A Breath of Fresh Air

It’s a fact: living in a city or other urban environment means dealing with pollution. But while it may seem unavoidable, there are untapped ways to improve the air quality of our cities. New research from a team including David Nowak and Robert Hoehn from the USDA Forest Service and Satoshi Hirabayashi and Allison Bodine of the Davey Institute has shown that adding more trees in urban areas can help reduce the negative effects of pollution.

A wide variety of pollutants contaminate the air we breathe and harm the atmosphere — ozone, sulfur dioxide, nitrogen dioxide and particulate matter, just to name a few. The new study examines the ways in which trees can help us deal with fine particulate matter, which is associated with increased risk of all-cause, cardiopulmonary and lung cancer mortality. While Environmental Protection Association (EPA) regulations have helped cut down rates of these early deaths and improved overall air quality, there is still more to be done…and more trees might be the next step.

Based on the fact that trees can absorb particles from the air as well as retain them on their surface until they are washed away by rain, Nowak and his team set out to study and quantify how trees are helping us breathe easier. They analyzed four areas in a number of U.S. cities:

  • Total leaf area in the city on a daily basis
  • The hourly flux of fine particulate matter to and from the leaves
  • The effects of removing the particulates from the air
  • And the health incidence impacts and monetary value of the change in particulate matter concentration

The results all pointed toward the need for more trees. The rates at which trees removed fine particulates from the air saved cities millions of dollars and reduced mortality by as many as 8 people a year.

Urban tree cover is only at about 35 percent in the United States, but hopefully the results of this study will lead urban planners and managers to keep in mind the benefits of investing in trees.

>>Read the full report here.


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