Laying the groundwork
Minneapolis completed a study of its urban tree canopy in April that is helping city leaders plan initiatives to plant more trees in the city. Using satellite imagery and geographic information systems, a team from the University of Minnesota analyzed the city's current tree canopy and identified potential locations for more trees.
The city's Sustainability Office started the project to establish how much progress could be made and needed to be made to expand the tree canopy, one of the sustainability indicators the city tracks. By increasing the number of trees, city leaders expect to reduce stormwater runoff and energy consumption.
The University of Minnesota's Remote Sensing and Geospatial Analysis Laboratory classified the urban tree canopy and other land cover using QuickBird satellite imagery, and Light Detection And Ranging (LiDAR) imagery. The images revealed that Minneapolis had an existing tree canopy of 31.5 percent (11,569 acres). Buildings, streets, water and other permanent features covered 31 percent. The remaining 37.5 percent (13,684 acres) — including parking lots and residential properties — require further analysis to determine if they could be transformed into canopy areas.
The team also detailed the tree canopy percentage for all sections of the city and ranked neighborhoods' tree canopies. Combining the parcel-based estimates with land use data showed that most of the land suitable for expanded tree canopy is in residential zones.
Minneapolis now has a digital GIS-compatible classification of tree cover, along with grass/shrubs, bare soil, water, streets, buildings and other impervious surfaces. Maps and statistics can be generated and used for setting tree canopy goals and planning for tree planting and maintenance. "With this project, we will now be able to make compelling cases for either targeting dollars to specific identified areas of need or to make pitches to funders for specific identified tree needs and for overall canopy expansion," says study leader June Mathiowetz, who is coordinator for the Homegrown Minneapolis program.
Many city departments and external partners contributed to the study's design. It was funded by a $29,000 Minnesota Department of Natural Resources' Metro Greenways grant and $2,000 each from the city and the Minneapolis Park & Recreation Board.
Project: Urban tree canopy survey
Agencies involved: Sustainability Office, University of Minnesota's Remote Sensing Laboratory
Date completed: April 2011