BURLINGTON, Vt.—Increasingly, trees are the new must-have for American cities.
Some prodded by environmental awareness, some by regulatory edict, they're stepping up tree plantings in hopes of improving air quality, reducing energy consumption and easing stormwater flows.
And a four-man team of scientists at the University of Vermont is helping urban planners and foresters gauge the existing "tree canopy" -- or cover -- in their cities and set realistic goals for increasing it.
Their expertise has been tapped by public and private groups in New York, Boston, Washington, D.C., and several Maryland towns eager to green their cities with the help of private property owners.
"Everybody's trying to do their best to improve tree canopies and work with developers and urban planners to make sure they remove as little tree canopy as possible in their projects," said Mark Buscaino, executive director of Casey Trees, a not-for-profit in Washington, D.C., that works to green the nation's capital.
"The benefits are many," Buscaino said. "First, there's the environmental. Trees cool things. They remove particulates in the air. They're linked to mitigating storm water flows, which is an enormous problem in all urban areas because there's so much impervious surface."
Generally speaking, tree canopy refers to the part of a city that's shaded by trees. But quantifying its size was once an elusive task.
The UVM scientists, working with a research scientist from the U.S. Forest Service, have used computer programs and their own expertise to combine satellite images with aerial photos and tax maps to ascertain tree canopy size and break it down by parcel, determining which trees are on public land and which are on private land.
Led by J. Morgan Grove, a research scientist for the Forest Service, geospatial analyst Jarlath O'Neil-Dunne and associate professor of natural resources Austin Troy, the group works out of a "spatial laboratory" in UVM's Rubenstein School of Natural Resources. The team has become a go-to resource on the growing trend in cities.
"If you don't even know what you have, you can't make any decisions," O'Neil-Dunne said. "It wasn't that people didn't want to plant trees or didn't want a tree canopy program. But they needed the hard data to make decisions. That's where we came in."
The group consulted on a study of Baltimore's ecosystem in 2002, and word of its pioneering methods spread, prompting forestry officials from New York, Boston and other cities to reach out to the team for help.
The group's expertise dovetailed with a growing awareness among elected officials that trees could be more than decorations for urban areas.
In addition to giving off oxygen, they cool the air, limit sun exposure and act as sponges for precipitation, catching rainwater and releasing it gradually instead of having it flow directly into storm sewers.
"These guys, in addition to being fun to work with, are really the ones who have pioneered a geographic information system and a graphic depiction of tree cover using aerial photographs and, more importantly, developed a management tool for analyzing the data that allows you to then set your planting targets," said Charlie Lord, executive director for the Urban Ecology Institute, in Boston, which worked with the group.
"They help you gather the data, analyze it and help you answer the basic questions -- 'Where do we have trees?' 'Where don't we have trees?' -- and the more sophisticated ones, like 'Where would we plant to improve our carbon footprint?' or 'Where are the best places to plant to improve our water quality?'" Lord said.
The group's work helped the city of New York establish the goals for a 1 million tree initiative that began last fall, aiming to plant that many trees over a 23-year period.
"It really kicked off everything, from a policy perspective, a natural resource management perspective, a planning perspective. It helped us set our sights on one million trees," said Fiona Watt, chief of forestry and horticulture for the New York Department of Parks and Recreation.
"People used to overlook trees in cities," Watt said. "They're now viewed as increasingly important because of the work of scientists who've helped us quantify those benefits. The environmental benefits and property value benefits are quantifiable, but the social ones are harder. They make us feel good, they improve our moods, they make neighborhoods more beautiful.
"Tree canopies can make neighborhoods more cohesive and bring people together, bonding them over this common resource," she said.
The fruit of the team's work may not be visible yet, but it will be eventually. In the world of forestry, there's an old proverb: "The best time to plant a tree was 20 years ago. The next-best time is today."
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