Traverse City staff and a consulting group have completed a full inventory of the city’s more than 10,000 trees – with the group's report providing new insights into the health and diversity of city trees, as well as recommendations for improving the city’s tree population.

Staff presented the report to Traverse City commissioners this week, summarizing the results of a two-year process that saw employees – with help from the Davey Resource Group – surveying 9,756 street trees and roughly 400 trees located in city-owned parks. Survey work included “walking from tree to tree” examining each one’s species, size, height, condition, position, and GPS location to create an updated city database, according to Parks and Recreation Superintendent Derek Melville. The last time the city undertook such an inventory was 1982.

The report highlights several pieces of good news: Traverse City has a nearly “ideal” mix of tree ages, ranging from young (48 percent) to established (26 percent) to maturing (15 percent) to mature (11 percent). Thirty-three percent of Traverse City is covered by tree canopy, with a majority of trees rated as being in good or fair condition. Davey Resource Group estimates that city trees remove more than 110,000 tons of pollutants from the air, intercept more than 21 million gallons of stormwater, and sequester almost 17,000 tons of carbon every year – an estimated ecosystem benefit of $2 million annually. In addition, “Traverse City’s community forest currently stores 505 million tons of carbon over its lifetime, valued at nearly $8 million,” the report found.

The report shows a boost in the total number of trees since the 1980s, when there were only 7,595 trees and shrubs counted. “We have more than 2,300 additional street trees in 2018 as compared to 1982,” the report states. “The increase can partially be attributed to the planting efforts of the city, but other factors” also play a role, such as re-categorizing trees located in traffic islands as street trees. Trees inventoried did not include those located in parks outside of official city limits, such as the Brown Bridge Quiet Area and Hickory Meadows. There have been significant plantings on those and other properties by both the city and other groups over the last five years; all combined, there have been 33,168 trees planted on city properties since 2013.

“We’re very excited about a lot of the outcomes,” City Manager Marty Colburn told commissioners about the report’s findings. “In recent years, the city commission has been very positive in giving the city staff additional resources to plant more and more trees, so we continue to invest…the value of our tree population is very important.”

The report also highlights potential threats and areas of concern with the city’s tree population, however. Half of all Traverse City trees – 50 percent – are maple trees, an imbalance that makes the population vulnerable to a devastating pest infestation. According to Davey Resource Group, a single genus like maple should comprise no more than 20 percent of the tree canopy. As many as 70 percent of city trees were maples in the 1980s, so the city has made notable progress through a concerted effort to vary the types of trees it plants annually. But it still faces a “biodiversity concern,” according to consultants. Percentages for the next most prevalent types of trees in Traverse City are considerably lower, including oak (12 percent), pine (7 percent), spruce (4 percent), and pear (3 percent). “Continued diversity of tree species is an important objective that will ensure Traverse City’s urban forest is sustainable and resilient to future invasive pest infestations,” the report states.

Davey Resource Group outlined several steps for city staff to begin undertaking immediately to boost the health and longevity of city trees. Chief among the recommendations is to plant at least 400 new trees annually – a goal the city is already close to achieving, with Melville noting that staff had planted 350 trees in 2018. The consulting group indicated “major roads and corridors present the highest opportunity for new plantings,” as well as open areas at the Grand Traverse Commons and locations throughout residential neighborhoods. A total of 480 acres of both public and private property were identified as ideal planting sites; if the city planted in those locations, it could increase its tree canopy from 33 to 43 percent. Consultants recommended city staff hold workshops and events to encourage private property owners to plant more trees on their land, in addition to the city’s plantings on public property.

Consultants also recommended watering newly planted city trees for two years to increase their chances of survival. If the city planted 400 trees per year, that would mean in year two the city would be watering 800 trees per year at an estimated rate of 20-30 gallons of water per tree per week. “We need to develop an efficient way to do that,” Melville acknowledged. Pruning was also highlighted as a major consideration, with Davey Resource Group recommending pruning 1,500 trees per year on a seven-year cycle. With pruning times ideal in winter, and without a dedicated forestry staff, Parks and Recreation staff have to juggle prioritizing things like plowing versus pruning trees, Melville said. “I can tell you that’s a scenario we are falling short on,” he said, estimating staff prune 500-600 trees in mild winter years and 400-450 during bad years when staff resources are needed elsewhere.

Davey Resource Group's recommendations could help city commissioners make funding decisions during their upcoming spring budget planning process, with the city needing to decide if it will eventually bring on a full-time forester, boost funding to Parks and Recreation staff to increase tree maintenance efforts, or potentially contract out some duties. “I think (the report) says we’re in a good place, but this is always going to be a continuing investment by the community," Colburn said.

City Planning Director Russ Soyring also noted staff are still working on a potential city tree ordinance that could require developers to replace trees they remove during construction and extend special protections to hillside and shoreline trees. A city survey is open to residents through February 6 soliciting their input on the ordinance and what types of regulations they would support regarding city trees. The city has already received 168 responses to the survey, with early feedback reiterating the public’s support of protecting the tree population.

“Eighty percent of people say they really want to preserve healthy urban trees, they think there’s a real public interest in doing so,” Soyring said. “This is something that’s really important to our residents and property owners.”