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Urban forest provides shade, savings for city of Cottage Grove

Despite the old adage that money doesn’t grow on trees, Cottage Grove Forester Steve Bowe has discovered that figuratively speaking, it just might.

With a software system called i-Tree, a suite created by the U.S. Department of Agriculture, Bowe has mapped out segments of the city’s urban forest population ahead of the upcoming emerald ash borer treatment season.

“In order to figure out where we’re going I had to put a dollar and cents figure to the trees,” Bowe said. “(i-Tree) basically takes that tree and makes the assumption of how much does aesthetics put into it, how much energy reduction. It’s all based on size and location of the tree.”

The program also puts a price tag on a tree’s air quality, stormwater retention and carbon dioxide emission.

Using the i-Tree software, Bowe priced out the existing 12,525 public trees in the city as a guide to purchasing trees in the future.

According to the results, there are nearly 3,700 green ash trees on city boulevards and public property. The second most populated tree is the Norway maple at 1,289, followed by the silver maple, honeylocust, linden and hackberry.

Each tree holds a different value, Bowe said. According to the i-Tree estimates, the green ash tree population saves the city more than $720,000 annually, with the majority of the savings attributed to aesthetics, energy conservation and stormwater retention.

Bowe said the crown spacing and height of the tree play a key role into determining the financial benefit.

A combined grouping of other varieties of trees aside from the six main trees, saves the city just over $297,000 a year. The third most economically beneficial tree, Bowe said, is the silver maple, which saves just under $231,000 annually.

The i-Tree software estimates that the variety of trees within the city is valued at more than $1.7 million.

Pioneer city for EAB prevention

With a solid EAB management plan in place, Bowe said Cottage Grove is “miles ahead” of surrounding communities.

With a process that combines premature tree removal and insecticide treatments, he said the city’s management plan is well known.

“We are on the Arborjet posters at seminars and we’re an example city by the Department of Agriculture (standards),” Bowe said.

Now three full years into the 12-year EAB management plan, Bowe said roughly 20 percent of the city’s ash trees have been removed, many through a voluntary removal and replacement plan.

“About one-third of the (city’s) forest is ash,” Bowe said. “So we still have a ways to go.”

Roughly $100,000 is allocated this year to treat about 65 percent of the ash population with EAB-preventing insecticide.

While the invasive beetle has yet to be found in Washington County, Bowe said it’s better to be proactive, rather than reactive.

“We want to manage the bug before the bug manages us,” he said.