To determine the future of the maple, the city of Missoula uses a device called a sonic tomograph. The Urban Forestry Division has catalogued an estimated 74 percent of municipal street and boulevard trees, and most of them are, to a trained eye, obviously healthy or obviously hazards in need of removal.
“The tree has a full canopy, but it clearly has a defect at the base,” said Christopher Gray, an arborist with the Urban Forestry Division of the Missoula Parks and Recreation Department. “Is this a high-risk tree? Low-risk tree?”