If you're looking for the shadiest place in Minneapolis this summer, head to the Lynnhurst neighborhood off the southeast shore of Lake Harriet.
The neighborhood ranks first in the city in the proportion of urban tree cover that blankets its homes, businesses and parks. Nearly 49 percent of its area, which includes a portion of Minnehaha Creek, is covered, according to a first-of-its-kind study of the city's canopy that used high-resolution satellite technology.
The study, by a team of University of Minnesota researchers, put the overall city rate at 31.5 percent, higher than previous estimates that used less precise methods.
In St. Paul, the canopy cover rate was 32.5 percent, a recent study found. Researchers also studied Woodbury, where the tree cover is 21.5 percent; it's lower because large portions of the city still are cropland, and trees in newer residential developments are predominantly younger and smaller, said Marvin Bauer, lead researcher and professor of remote sensing at the university's Department of Forest Resources.
Recent similar studies put the Twin Cities in the middle of urban areas, less than Washington, D.C., at 35 percent, and more than Boston at 29 percent. Other cities include Baltimore (49 percent), Burlington, Vt., (43 percent), Des Moines (27 percent) and New York (24 percent).
The study's findings were good news for Minneapolis project coordinator June Mathiowetz, who said the city's estimated 979,000 trees offer many benefits.
They suck up water that would otherwise wash onto streets and flood stormwater pipes. They clean the air. They increase the attractiveness of homes, usually driving up property values. And they shade homes and businesses, reducing the need for cooling during hot summer days.
"In terms of energy conservation, it doesn't get any easier than planting a tree on the west side of your house if you can," she said.
The study used high-resolution satellite technology to study the city from above on a clear and cloudless June 29, 2009. It recorded and analyzed how much tree cover there was on each individual property in the city, as well as on blocks and in neighborhoods.
The study also shows gaps in the urban tree cover. Those could help city planners and foresters target areas such as boulevards and parkland for additional tree planting, or develop low-cost programs in certain neighborhoods to encourage more saplings on private land.
Those future activities are the "real payoff" of the study, Bauer said. "Our maps are simply the starting point or baseline for what [the city] will be doing," he said.
The research also provides a useful benchmark to watch how the urban canopy changes in the future as some species succumb to old age, invasive pests and other problems, said Ralph Sievert, director of forestry for the Minneapolis Park and Recreation Board. "Because of the emerald ash borer coming, it's nice to know the percentage of the canopy cover to begin with, because we haven't removed many ash trees yet."
Sievert said about 22 percent of the city's trees are ash, and if thousands of mature trees are lost, the canopy will take a hit for a few years.
"You can plant a lot of new trees," he said. "The problem is that it takes awhile for them to catch up in terms of the canopy that they're providing compared to the trees that are taken out."
Other neighborhoods that rank high in shadiness contain large residential lots and extensive parkways, scattered mostly along Minnehaha Creek in south Minneapolis, West River Road, and the city's western border. In terms of total acreage that's shaded, the Linden Hills neighborhood, bordering parts of Lake Calhoun and Lake Harriet, was tops. The study included 84 neighborhoods and three industrial areas. Most of its $23,000 cost came from the Minnesota Department of Natural Resources.
A 2004 field study, which relied on extrapolations and was much less accurate, estimated that trees covered 26 percent of Minneapolis.
Sievert said the city has increased its tree plantings on boulevards and other public land. It will plant 4,000 trees this spring and 1,500 saplings in the fall, compared to 3,000 in recent years.
Spring planting began Wednesday and will continue through May, he said.
The U study also calculated what is under the tree canopy across the rest of Minneapolis: grass and shrubs (about 20 percent), buildings (15.5 percent), streets (9.5 percent), water (6.2 percent), and other impervious surfaces, such as driveways, sidewalks and parking lots (17.5 percent).
Mathiowetz said it's important to be more strategic about managing the city's urban forest as a great resource.
"If you're investing in a tree and it needs to last for more than 30 years, you want to know if your techniques are working," she said. "Trees are legacy work."
Tom Meersman • 612-673-7388