iTree

Calculate the value of the urban forest

For David Nowak, making urban nature a policy priority requires hard, dollars-and-cents data. Cool interactive maps help, too. Nowak, a research forester with the U.S. Forest Service in Syracuse, New York, is out to provide both. After conducting comprehensive assessments of trees in half a dozen major cities, he’s now in charge of iTree, a suite of open-source software introduced in 2006 to model the ecosystem services provided by urban trees.

Anyone, from city planners to curious citizens, can enter some basic information about a tree—its size, species, location—and iTree quantifies what the tree contributes to pollution removal, carbon storage, and mitigation of building heating and cooling costs. It scales up, too: enter data on a citywide sampling of trees, and the program computes the value of the urban forest as a whole. Ecosystem services provided by street trees in Minneapolis, for example, are worth $15.7 million per year.

With those kinds of numbers, city leaders are taking notice: iTree data have inspired cities including New York and Baltimore to set ambitious tree-planting goals. About 10,000 copies of iTree have been downloaded so far. Environmental consultants, university students, local governments, and nonprofits have used the software in projects across the U.S. and in Canada and Australia, too. Novak’s team is tweaking the model so it can handle data from Colombia and Brazil.

“iTree is basically a calculator right now,” Nowak says, but he has even bigger goals. A new module, for example, links to Google Maps to help homeowners and landscape architects see the effects a tree would have if planted in a certain place on a specific lot. In the next version of the software, to be released in 2014, Nowak wants to enable modeling of trees and their ecosystem services 30 to 50 years into the future—for example, projecting how climate change may shift the distribution of different tree species and guiding planners to plant trees now that will continue to do well under future climate conditions. If the preliminary data are any indication, the return on investment will be pretty good. ❧

—Sarah DeWeerdt

Art: Digital Tree ©Astralsid

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