Reported December 2007

BACKGROUND: The city of Baltimore, Maryland, has a goal to double the number of trees by 2036, in order to improve both aesthetics and air quality. But before they can do so, the need to know how many trees they already have and how healthy those trees are. So the city is conducting a high-tech “tree survey” using i-Tree software, available for free from the US Department of Agriculture’s Forest Service.

ABOUT THE SURVEY: The survey involved inspecting the trees on 500 randomly selected city blocks. Armed with handheld computers and an assortment of field guides, volunteers gathered such information as the trees’ size, species, whether there were any dead branches and whether any of the trees pose a threat to wires or sidewalks. This data is then fed into the i-Tree computer software package. At the survey’s end, the software will analyze how much the city’s public trees improve air quality, conserve energy, control storm water and increase property values. It can even estimate those improvements in dollar amounts. City officials expect i-Tree to demonstrate to policy makers and the public that the city’s trees are worthwhile, and that more trees are needed. Perhaps it will even inspire residents to plant more trees on private property.

HOW DO TREES IMPROVE AIR QUALITY? Photosynthesis is the process of converting light energy to chemical energy and storing it in the bonds of sugar. This process occurs in plants -- including trees -- and some algae. During photosynthesis, trees remove carbon from the atmosphere and store it away as they make energy in the tree’s wood. This process is known as sequestration, and it reduces levels of carbon dioxide in the air. Trees also provide shade and lower air temperatures, reducing the amount of energy that buildings use and, therefore, the amount of work required -- and CO2 emitted -- by power plants. Trees with denser wood, such as hawthorn trees, are most effective at removing CO2 from the air. Other trees emit compounds that contribute to the formation of ozone. Ozone in the upper levels of Earth’s atmosphere can have a protective effect, but particles of ozone in the air we breathe are considered pollutants.

The American Geophysical Union contributed to the information contained in the TV portion of this report.

If you would like more information, please contact:

Dr. Rebecca Feldberg
Arborist
(410) 396-6109
Rebecca.feldberg@baltimorecity.gov

American Geophysical Union
Washington, DC 20009-1277
(800) 966-2481
http://www.agu.org

DID YOU KNOW?

About 20% of Baltimore’s land lies under trees, compared with a 27.1% average for cities nationwide. Baltimore city officials would like to double that percentage to 40% by 2036.

ON THE WEB...

i-Tree: Tools for assessing and managing Community Forests

City of Baltimore, Maryland