An urban forest might sound as far-fetched as a rural subway. But New York City already has more than five million trees, and these create a canopy that shades 24 percent of the city according to a 2006 study by the US Forest Service and UVM's Spatial Analysis Laboratory. While not a moose-filled wilderness, New York's urban forest exists now: cooling city streets, soaking up rainfall and carbon, reducing pollution that triggers asthma, and making twiggy homes for New Yorkers' beloved birds.

Still more trees are needed. Which is why a dozen UVM students at the Rubenstein School of Environment and Natural Resources are speaking by videoconference to Fiona Watt, New York City's chief of forestry. Together, they're looking for places to put a million new trees.

Big apple trees
Graduate student Dan Erickson points to a digital map of Brooklyn he and his classmates created with a geographic information system (often called a GIS) program in a lab in the Aiken Center, while Watt and other officials watch the presentation on computers in New York.

"It looks like some kind of fungus is growing in those areas," Erickson says, pointing to several neighborhoods covered with spots. Each spot of the "fungus" Is actually a vacant lot, he explains. "These might be good places to plant trees," he says. Overlaying this data with other information, like asthma-related hospitalizations, he identifies a few areas in the borough as top priorities for new trees.

Erickson and his classmates, mostly undergraduates, spent four days in August 2008 tramping around the city, studying its trees, meeting neighborhood groups, and collecting data. It was the beginning of Natural Resources 378/285: GIS Analysis of New York City's Ecology.

Led by three scientists who have been working with officials in New York for several years — Austin Troy and Jarlath O'Neil-Dunne from UVM and Morgan Grove from the Forest Service — the students saw New York's realities: burgeoning population, disappearing open space, increasing summer heat brought by climate change, and the city's current tree stock enduring life in a concrete jungle.

In 2007, Mayor Michael Bloomberg announced an ambitious goal using analysis from the UVM and Forest Service team: plant a million trees in the next decade. More than 125,000 trees have been planted since the MillionTreesNYC campaign began.

But there's a problem: all the $400-million Bloomberg allocated to the Parks Department is for trees — and none for planning where to plant them. How to add another 875,000 trees by 2017 — on what land, in what neighborhoods, with which stewards, at what cost — remains an open question.

Arboreal accuracy
As the students' slides roll by, the answers seem closer. The city has extensive data on land use, existing trees, pollution, parks, pavement, stewardship groups and the like but not the resources to fully explore it. UVM has the technical expertise — and student labor — to analyze this information, searching for a balance of suitable planting locations with neighborhoods in need.

"A tree is a living organism that has to be planted but also cared for," says graduate student Loona Brogan, and that means creating a more complex plan than simply finding empty lots and plopping in trees. "It takes a lot of time and resources to do spatial analysis, and we have tools to help the city," she says.

Though final plans and decisions will, of course, rest with city officials, Erickson and his class partner used the skills they have been developing in the course to identify Bedford, Crown Heights North, Bushwick and a few other areas of Brooklyn as potentially good places for new trees.

"We don't want a million dead trees," says Dexter Locke '09, whose group assessed Manhattan and developed a planting prioritization based on reducing urban "heat islands" and improving air quality. "This is real service on a real problem, "he says.

The four-day field trip to New York was essential, says Austin Troy, an associate professor who organized the course. "It's so easy with GIS to be completely abstracted — you don't get a sense of the people, the neighborhoods, the significance of real world constraints," he says. But on the other hand, without the spatial data and remote imaging, many opportunities and best-odds locations would be missed.

Troy and Morgan Grove had been working together for several years with Fiona Watt and other officials in New York helping them to measure and quantify their existing urban tree canopy and how much plantable area there might be. It's part of a larger effort that they've been championing to help cities around the country understand and enhance the value of their urban forests.

"What the students are doing here is useful in New York," Grove says, "but also for our work in other cities from Burlington to Washington, D.C."

"It's amazing to see so many projects with our data," Fiona Watt says via speaker phone, as the students complete their video presentations. "We'd have to commit our GIS person to a year's worth of work to come up with what your class did in a few weeks."