UA News

The 2,000 trees that line campus roads clean the air, reduce storm flooding and cut utility costs.

A new inventory of "street trees" at The University of Arizona shows they do more than provide pleasant vistas and an oasis in central Tucson. The more than 2,000 trees that line campus roadways sequester carbon from the atmosphere, reduce pollution and flooding and save the UA a bundle on cooling costs.

The study, conducted by the UA Campus Arboretum, documented individual trees, their distribution and compared their yearly costs and benefits, said Elizabeth Davison, director of the Campus Arboretum. 

Davison said the street trees and other trees at the University are a significant factor in reducing the UA's carbon footprint. The study included only those trees that directly flank campus roads. 

Each year, the UA's street trees:

• sequester 246,620 lbs of carbon dioxide (CO2).
• reduce the energy costs for UA facilities by $18,230.
• reduce emission, pollutants and particulates by 9,994 pounds.
• intercept more than a million gallons of rainfall or storm water.

"These street trees contribute to the quality of life for all our neighbors, providing shade on pavements, and reducing air pollution, storm-water and the University's ‘carbon footprint'," said Davison.

There are more than 7,000 trees within the UA's boundaries, including the street trees. Davison said that many of the largest trees are in the interior of campus, and that some of them are among the oldest trees in Tucson. 

Robert Forbes, the first head of the UA Agriculture Experiment Station, planted olive trees on the west side of campus at the end of the 19th century, part of his experiments with tree crops from Mediterranean countries.  Those trees, most likely bought from a nursery in Santa Barbara, Calif., were Spanish, French and Italian in origin.

In all, Davison estimated that the combined benefit of the UA's urban forest could be three to four times higher than for just those trees listed in the current study.

The age and size of trees also factor into their effectiveness.

"As trees age, their benefits rise, but then may fall," Davison said. "As we plant more small trees, we ensure increased potential benefits for ensuing years. As older trees are removed, the ratios shift. Sometimes an older tree is less efficient in stormwater uptake, but it holds more carbon in its trunk and branches." 

More information is on the Campus Arboretum Web site.