Loring Park. Photo by Sarah McKenzie

Loring Park. Photo by Sarah McKenzie

Tracking the state of the urban forest

Updated: June 23, 2016 - 3:01 pm

The city’s tree canopy continues to face threats from the emerald ash borer and strong storms.

Minneapolis’ tree canopy is estimated to cover around 25 percent of the city, down from about 32 percent in 2009 — the last time the city did an extensive study of the tree canopy using satellite imagery, said Peggy Booth, co-chair of the Minneapolis Tree Advisory Commission.

Since then, the emerald ash borer has spread to trees throughout the city and other trees have been lost to the 2011 North Minneapolis tornado and other major windstorms. New development projects have also resulted in the loss of hundreds of trees, Booth said.

The Park Board has slowed the spread of emerald ash borer by detecting and removing infested trees, but the disease is expected to claim many more trees in coming years. It has now spread to 28 neighborhoods in the city.

Source: Minneapolis Tree Advisory Commission
Source: Minneapolis Tree Advisory Commission

As part of its Ash Canopy Replacement Program, the Park Board has a goal of removing 5,000 ash trees annually and planting new public trees.

“As we loose these trees, we lose a lot of benefits that an urban forest provides to us,” Booth said.

The many benefits included improved air quality, improved public health and stormwater management, among other things, she said.

The Park Board planted 7,817 trees in parks and boulevards in 2015, according to the Minneapolis Tree Advisory Commission’s annual report presented to a City Council committee on Monday. Park leaders have worked to diversify the urban forest. Trees planted last year included 127 different species.

The City of Minneapolis also provided more than 1,300 trees to residents last year through the City Trees Program, a collaboration with the local nonprofit Tree Trust.

The city’s tree canopy should cover about 40 percent of Minneapolis, according to recommendations from American Forests, the nation’s oldest national nonprofit conversation organization, Booth said.

To reach that goal by 2040, the city would have to add 600,000 new trees — about 25,000 trees a year. The massive planting effort would take work from both the public and private sectors, Booth said.

The Minneapolis Tree Advisory Commission has several recommendations for city leaders to strengthen the urban forest, including saving existing healthy trees, funding a full-time forest preservation coordinator, expanding tree planting, guaranteeing the care of public trees, involving the commission in the review of development projects and commissioning another study of the canopy using satellite imagery.

Booth expressed concerns that the commission wasn’t involved in reviewing plans for the Sculpture Garden renovation, the Nicollet Mall project and the new Wirth Adventure Center.

The Sculpture Garden renovation has resulted in the removal of 400 trees, she said.

“We really feel that conserving trees was not a value that was put into the project from the beginning, and when we were informed about it was really to late to make a difference,” she said.

As for the Nicollet Mall project and the redevelopment of the Nicollet Hotel block, crews will be removing 151 trees and planting 251 trees and 214 shrubs, said Casper Hill, a spokesman for the city. Grasses and perennial ground covers will also be planted on four blocks, he said.

At a glance: Tree resources

— Tree Trust: An organization focused on strengthening urban forests. (treetrust.org)

— Brewing a Better Forest: A nonprofit group of arborists passionate about trees and craft beer. The organization has an Adopt-A-Tree program. (brewingabetterforest.com)