U prof maps trees for city planning

A city-wide tree canopy map shows where trees are needed.

by Emily Cutts

More than 30 percent of Minneapolis is covered in tree canopy, but thereâÄôs room for twice that.

Areas with housing currently have the highest tree canopy percentage and provide the most potential for more trees, according to a survey conducted by University of Minnesota professor Marvin Bauer and graduate students Don Kilberg and Molly Martin.

Adding more trees in both urban and suburban environments would not only help to beautify the area, but help reduce storm water runoff and conserve energy, the researchers said in the report.

In the case of energy conservation, Bauer gave an example of trees providing shade during the summer, thus reducing the need for air conditioning.

Bauer, director of the UniversityâÄôs Remote Sensing and Geospatial Analysis Laboratory, got a contract with the city of Minneapolis to study tree cover.

To create the map, Bauer, Kilberg and Martin used remote sensing imagery, like Google Earth, instead of on-the-ground counting of individual trees.

“But we go one step further, a big step, compared to what you find on Google Earth, which is simply the pictures,” Bauer said. “We take that data and classify it into the various land cover types.”

Bauer said the maps create a baseline for what is currently in the city. The information can then be used for future tree planting and management.

John Uban, landscape architect and a chairman of the Minneapolis Tree Advisory Commission, said planners use strategy when planting, rather than just lining the streets with trees.

“Trees are the Swiss Army knife of environmental benefits,” Uban said.

The report was presented in mid-April to the Minneapolis City CouncilâÄôs Regulatory, Energy and Environment Committee.

The last report the city had done in 2004 showed the canopy at 26 percent coverage.

That study, however, was a statistical analysis, where researchers used samples to estimate overall coverage, said Ralph Sievert, director of park forestry for the Minneapolis Park and Recreation Board.

BauerâÄôs study will be more accurate because of the use of satellite imaging, Sievert said.

Across the country, other cities have mapped their tree coverage. Various studies in the past five years show Washington, D.C., at 35 percent, Des
Moines, Iowa, at 27 percent and New York City at 24 percent. The Minneapolis campus has just more than 19 percent.

Even though BauerâÄôs map includes the University campus, a separate map of tree coverage is being created at the University.

The University has had an inventory of the trees on campus for longer than 30 years, said Lester Potts, who started working in Facilities Management at that time.

Over PottsâÄô career, the amount of data in the inventory has grown dramatically.

The University has been working for more than a year updating the inventory, adding information about tree diameters, health, any disease treatment and more.

“You know where you got to go, what you need to take with you to get it done,” Potts said. “It helps you plan things out further. If you have a limited amount of financial resources âĦ you can set priorities and better manage them.”