Just as St. Paul is ramping up efforts in its multiyear struggle to combat emerald ash borer by removing ash trees across the city, a national report is pointing out disparities in leafy canopies among neighborhoods nationwide, including locally.

A new Tree Equity report by the nonprofit American Forests reveals tree cover disparities along race and class lines in many cities. The group gave St. Paul an equity score of 83, which indicates the city is performing well overall, but with some neighborhoods lacking suggested tree cover.

The biggest disparities are on private property, not on city boulevards and parks, according to city officials.

The importance of tree coverage has grown in recent years as concern for climate change and heat islands grows.

Tree cover has become a point of concern particularly in St. Paul, where the emerald ash borer was first found in Minnesota, in the St. Anthony Park neighborhood in 2009. Though many communities across the state have battled with the invasive species, it's been a particular blight in St. Paul.

The city partnered with the Port Authority in June for $18 million in bonds to fight the crisis. Forestry professionals hope to control the proliferation of the destructive beetle and get back to planting, not removing, trees.

A neighborhood with fewer trees is significantly hotter than a neighborhood with more trees. One tree can have the effect of 10 room-sized air conditioners, said Karen Zumach, director of community forestry at Tree Trust, a Twin Cities nonprofit that works to grow the urban forest and new jobs.

The national report, released last month, sets a goal of getting every neighborhood block group in a city to a score of 75 or higher, based on how tree canopy and surface temperature align with factors such as income, race, employment, age and health. In St. Paul, 42 of 249 block groups fell below 75.

Minneapolis scored slightly higher overall with a score of 86. Of the 378 block groups there, 49 fell below a score of 75.

The report estimates that 69,889 trees would need to be planted in St. Paul to get each block to an equity score of 75. Neighborhoods in St. Paul with higher populations of people of color or lower incomes have fewer trees and a lower equity score compared to neighborhoods with fewer residents of color or people in poverty.

Rachel Coyle, who manages the city's forestry work group within the parks department, said the city is aiming to plant a canopy cover citywide. The report doesn't account for the difference between public and private tree canopy, she noted.

"While we are responsible for the urban forest, we can really only plant on public properties. We can promote the planting of trees on private property, but we can't necessarily make that happen," Coyle said.

Canopy cover is pretty equitable in parks and along streets, she said: Every open site is planted regardless of neighborhood.

The department does outreach with specific neighborhoods to promote planting on private lands, she added.

Zumach, who also serves as the vice president of the Minnesota Shade Tree Advisory Committee, agreed there has been a significant effort in equity on public lands, with the biggest discrepancies on private property.

Neighborhoods with less tree canopy are often lower-income areas with more rental housing, where tenants have less power to plant a tree on a property that's not their own, Zumach said.

Property owners who do plant trees will see an increase in property value, in addition to the larger neighborhood benefits that trees provide, she said.

"We have that component, we have that reduced energy cost, we have the improvement in the air quality throughout the community, where those trees are planted," Zumach said.

Achieving equity is complicated by emerald ash borer infestation, as St. Paul and other cities lose trees and face devastation on private land, too, Zumach said.

"We're all losing trees pretty equally across the cities right now, because of emerald ash borer, which doesn't really care if you're in a high-income or a low-income area of the city," Zumach said. "That tree is more than likely going to die unless it's been treated."

Now, cities can be even more intentional and equitable about where replacement trees are planted.

"I think the tree equity score is a really useful tool to open the eyes of those who are making decisions on where money is spent in communities. We know that we can see where trees aren't," Zumach said. "Working with community groups and neighborhood groups, and those who are working really hard on the ground to help make that change, I think is really important."

Zoë Jackson is a reporter covering St. Paul and its neighborhoods for the Star Tribune.

612-673-7112 • Twitter: @zoemjack