Surveying Duke's Valuable Trees

An ongoing inventory of campus trees shows their economic and environmental value

During Durham's warm spring and summer months, the shade of trees across Duke's campus can be invaluable. But those trees themselves, it turns out, are worth millions.

Since November 2011, two Duke graduate students have partnered with Facilities Management to work on a pilot program that will survey thousands of trees across East, Central and West campuses to determine the economic and environmental value of Duke's trees. Using an open source program called i-Tree, a collection of about 1,200 Duke trees - less than 10 percent of trees managed by Facilities' grounds crews - is valued at millions of dollars.

Duke is among a growing number of college campuses using the computer program, including Purdue and Auburn universities. I-Tree was created and is made available for free by the U.S. Forest Service. The work is part of continued campus landscape analysis by Facilities Management, which includes studying trees, turf and planting across about 350 acres. The goal is to better understand the natural landscape of Duke.

"Using i-Tree is part of our whole system of maintaining and caring for our trees," said Roger Conner, superintendent for Duke Grounds. "By learning more about them and even giving them a value, we're better able to use the data to care for these important assets."

Value of trees is determined through several factors, including aesthetics, ability to capture carbon, storm water interception and more. In addition to a replacement value of millions of dollars, the roughly 1,200 surveyed trees have also been determined to provide about hundreds of thousands of dollars in storm water infrastructure that prevents soil erosion and runoff and carbon capture.

Jason Elliott and Katie Rose Levin, students in the Nicholas School of the Environment's Master of Forestry program, have been working to perfect the system of surveying and valuing trees so formal surveying can begin later this summer. The goal is to inventory about 5,000 trees.

When studying a tree to determine its worth, Elliott and Levin document a tree's size, species, condition and approximate age. That information is then plugged into i-Tree, which offers a monetary value based on data from the Forest Service and users of i-Tree, which include cities and organizations across the country.

"It's easy to think about it in terms of a bottle of wine," Elliott said. "As a bottle ages, its value goes up because of the scarcity of finding that vintage again."

In addition to providing price to trees across Duke, the i-Tree surveys will also serve a practical means of getting an idea of all the trees across campus. An up-to-date inventory means Facilities will have an easier time knowing how to treat and care for the variety of trees scattered throughout Duke.

View the video below to hear Katie Rose Levin explain the i-Tree survey process: