Regional trees surveyed, counted

By Darryl Holliday

The Morton Arboretum completed its 2010 Tree Census, August 27, and while they didn’t exactly count all of the trees in the city, they did check around 14,000 points in the seven county region. Due to a 2009 study of Chicago’s urban trees, this year’s census instead focused on the suburban areas, otherwise known as Chicagoland.

Members of the team were given what Beth Corrigan, community tree assistant at the Arboretum, called “dots in space”—points within the Chicagoland region whememberswere sent for analysis. The dots, randomly generated by a computer, were then tracked down by teams using aerial photographs, maps and triangulation.

Sometimes the dots in space ended up in the middle of cornfields, highways or other treeless zones.

“They literally fall everywhere that you can imagine,” Corrigan said.

One search crew had to access a tree island by canoe while others trudged across northeastern Illinois wearing mosquito hoods in search of their objective.

After finding a specific location, the teams determined a 37-foot radius—nearly a 10th of an acre—where they would identify, measure and count all of the trees within the circle.

“But it’s more than counting trees,” Corrigan said.

Data from the tree census will be used to measure the Chicago region’s urban forest.

“The net effect of the urban forest is positive,” said Greg McPherson, a research forester with the United States Department of Agriculture’s Forest Service. “It’s beneficial on our pocket books and beneficial in terms of our health and welfare, whether it’s our mental health or the quality of the environment.”

The trees and plants covering the city provide a long list of benefits from shade to the interception of gaseous pollution including ozone, nitrogen dioxide, sulfur dioxide and carbon emissions. They also absorb various other particulate matters that can harm lungs.

According to the USDA’s 2009 “Assessing Urban Forest Effects and Values” study, Chicago’s nearly 4 million trees stored 716,000 tons of carbon for the year and removed a total of 888 tons of overall pollution from the local atmosphere. The report estimates the value of the pollution removed through the city’s trees was $6.4 million.

Results from the Morton Arboretum tree census, along with the 2009 USDA study, will offer comprehensive data on the urban forest’s environmental impact. The data will then be used as an indicator for future development in order to best serve the city and its residents.

“I think the urban forests are important because they provide nature where we work, live and play,” McPherson said.

Or as Corrigan put it, “The urban forest is all around you.”

According to Rosa Calderon, public affairs officer at the Chicago Department of Streets and Sanitation, the Bureau of Forestry—which began as a tree committee in 1909—is responsible for maintaining the 520,000 parkway trees in the city.

“More and more residents need to be aware of the benefits of the urban forest,” Calderon said. “But there’s always room for improvement.”

The tree census, in conjunction with various analyses of the city’s urban forest, hopes to do exactly that.

According to Corrigan, results from this year’s tree census won’t be expected until this winter, but city residents can expect to find an increasingly comprehensive view of the local environment.

“The whole idea is that this will give us what trees are out there but also what’s not,” Corrigan said. “Not only will we get an idea of the percentage of the Chicago region that’s planted, but also where the opportunities lie.”