What is a tree worth? Value of city trees is featured in Wilson Quarterly
Jill Jonnes’ insightful article “What Is a Tree Worth?” in the Winter 2011 Wilson Quarterly offers a comprehensive history of urban trees in the U.S., from Thomas Jefferson’s appreciation of trees in 1793 to Nebraska’s declaring the first official Arbor Day in 1874 and Theodore Roosevelt’s comment in 1905: “A people without children would face a hopeless future; a country without trees is almost as hopeless.”
The article traces the first municipal tree planting efforts in Chicago in 1911 to the 1970s, when many in U.S. cities watched as “graceful old elms, big oaks, and verdant small woodlands disappeared, victims of Dutch elm disease, development, and shrinking municipal budgets.”
Most importantly, it describes the development of scientific models and software to assess the value of city trees. The quantifying process began when Chicago arborist Edith Makra, tasked with increasing Chicago’s urban forest, contacted Rowan Rowntree, a U.S. Forest Service scientist, for help. Rowntree recruited two students he’d been training at State University of New York (SUNY), Gregory McPherson and David Nowak. They conducted a study that quantified the amount of air pollution that Chicago’s trees removed. This led to studies of other benefits provided by city trees, such as energy savings and stormwater management, and to the establishment of the U. S. Forest Service’s Pacific Southwest Research Station Center for Urban Forest Research in Davis, California.
In 2003, the U.S. Forest Service worked with McPherson’s and Nowak’s models to create i-Tree software for assessing the value of city trees, and the Davey Tree Expert Company enlisted University of California-Davis graduate student Scott Maco to refine it. One offshoot is the Tree Benefit Calculator, developed by the the Davey Tree Expert Company and the Washington, D.C.-based nonprofit Casey Trees. The calculator, which can be found on Friends of Trees’ web site, helps people determine the value of their own trees based on species, size, and geographical location.
In 2007, Portland Parks & Recreation used McPherson’s and Maco’s calculations to assess the value of Portland’s urban forest. They found that Portland’s trees provided $3 million in air cleaning and carbon fixing and $36 million in stormwater infrastructure cost reductions a year. The study was intended to help Portland achieve its 2004 Urban Forestry Management Plan goal of increasing tree cover from 26 to 33 percent.
Recently, U.S. Forest Service Geoffrey Donovan’s Portland-based studies have shown additional benefits from city trees, including reduced crime rates, higher birth weights, and higher home values for both the owner of trees and nearby neighbors.
To learn more about Portland’s efforts to increase its tree canopy and the environmental and economic benefits the trees provide, read yesterday’s story on this blog, Growth Rings.
In “What Is a Tree Worth?” Jonnes concludes:
“While science and technology are transforming and expanding the way we think about trees, Rowntree, now a scientist emeritus with the U.S. Forest Service, estimates, ‘We are only 50 percent of the way to knowing what trees really do for us.’ What we have learned only proves the old proverb truer than ever: ‘The best time to plant a tree was 20 years ago, the next best time is today.'”
–TR