Twin Cities suburbs turn to technology to identify troubled trees

Eric Akers spends his days driving around cities in a truck with a machine on top snapping photos and sending out invisible pulses of light.

Occasionally, someone strikes a pose, mistaking him for the car that makes Google Maps. But Akers is creating something different: a “smart tree inventory” that logs the height, diameter, branch patterns and other data on trees along the roadside.

“It’s the creme de the creme” in new tree technology, said Plymouth City Forester Paul Buck, who has been working with Davey Resource Group and tree data firm Greehill to create a database for the city. Plymouth and Bloomington are the first two cities in Minnesota to use the new tool.

Forestry teams throughout the Twin Cities metro area have been especially busy in recent years, as a combination of drought, severe storms and the emerald ash borer toppled scores of trees that gave many suburbs their character. Now, some teams are turning to new technology in hopes it will speed up their work and improve their efforts to increase the diversity and resilience of their tree canopy.

“This inventory will give us the data to make decisions around urban forestry for many years to come,” said Dave Hanson, assistant director of parks and natural resources for the city of Bloomington.

Forestry crews would typically send teams out to walk local streets and paths in their communities and log various details on each tree they spot, a process that can be somewhat subjective, Buck said.

When creating a “smart tree inventory,” techs like Ackers drive around a city with lidar — light detection and ranging — tools that collect thousands of points of data that can be used to gauge the health of a tree.

After the scanning is done — a process that often takes two to three weeks, depending on the weather and how much ground a city wants to cover — another team refines the data, to build a database that city workers can access.

The database holds information on each tree’s species, height, diameter and, in some cases, even calculations on how much carbon dioxide it removes from the air. City crews can then sort the data to try to find outliers.

“The computer can’t tell us what’s wrong, but it can tell us those trees were different,” Buck said. “Now, we can do some follow-up on those trees and say, ‘What’s going on with those specific trees? Are they dying?’”

Bloomington is paying about $386,000 for the tree inventory, plus help creating a long-term plan for the city’s tree canopy. Plymouth is paying about $320,000 for its inventory; Buck estimated that a traditional tree count would have cost about $280,000. City officials say they’ll be watching in the coming years to see if the investment pays off.

“It is sometimes a little nervous to be the first one, because you’re putting yourself out there,” Buck said. “It’s like anything that’s new: it’s change.”