In urban settings, trees benefit both water quality and human health. They moderate temperatures and beautify neighborhoods. They provide habitat for birds and shade for park benches.
But, while urban trees might not need a public relations campaign, they could use some organizing.
That’s the goal of the Urban Tree Canopy Strategy, a document that will be released by the Chesapeake Bay Program’s Forestry Workgroup in March for public input. Based on the goals of each state in the watershed, the strategy aims for a net gain of 2,400 acres of tree canopy in urban areas of the Chesapeake Bay by 2025.
“People are focused on stormwater and retrofits and rain gardens,” said Julie Mawhorter, who has led strategy meetings as the mid-Atlantic urban and community forestry coordinator for the U.S. Department of Agriculture Forest Service. “We know trees provide multiple benefits, but we’re not really investing in that.”
A decade has passed since the Bay Program established its first urban tree canopy directive. During that period, stakeholders found that the push for more trees needed to be more calculated. About 75 stakeholders gathered in mid-October for an Urban Tree Canopy Summit to develop a broader strategy, which should be finalized later this year after receiving public comments.
Mawhorter said establishing a goal for additional trees in the watershed was difficult because most states don’t know how many urban trees they have already and because the states have disparate definitions of an “urban tree canopy.” While the technology exists to measure that canopy from a bird’s-eye view, such high-resolution data have been collected only for portions of the watershed and at different times.
One of the Forestry Workgroup’s first steps is to work with the U.S. Geological Survey and the Bay Program’s Land
Use Workgroup to collect accurate urban tree data.
For now, the Forestry Workgroup is casting a net over the Bay states to collect the tree-counting numbers that do exist.
Marcia Fox, an environmental scientist with Delaware’s Department of Natural Resources and Environmental Control, said an urban tree canopy assessment existed for each of the nearly 60 municipalities in her state. But those assessments need to be updated, and their information doesn’t extend into developed portions of the surrounding counties.
Mawhorter said that, broadly, the term “urban tree canopy” refers to “trees where people live,” which could include trees in semi-rural portions of the states. Agricultural lands and forestlands would not be counted as part of the urban tree canopy, but there are some gray areas of land use in between.
For Bay Program modeling purposes, the canopy definition gets even more specific, distinguishing between “urban forests” of tree clusters and standalone trees in otherwise concrete landscapes.
“When you think of urban tree canopy versus a forest, what does it achieve in terms of water quality? Is it trees over pavement or lawns or unmanaged understory?” Peter Claggett, a USGS geographer, asked during his presentation to the Forestry Workgroup in early February.
He was explaining to the workgroup how the Bay models distinguish between different types of canopy and asking for feedback about the fairness of the model (which he got in spades).
But many of the state representatives were just as concerned about how to fairly count the trees that are being planted, protected, maintained or removed in their states.
Fox said on a call with the forestry workgroup that the goals for Delaware — to increase urban tree canopy by 50 acres in its portion of the watershed — would benefit from a stronger definition and updated assessments.
“We try to be realistic with some of these goals, given that we’re also working with the emerald ash borer and other issues,” she said, referring to the invasive pest that has the potential to wipe out much of the existing canopy in states with high ash populations.
In other parts of the watershed, the biggest obstacle to gaining trees is the sheer number of them lost each year to development and urban sprawl.
Frank Rodgers, executive director of the Cacapon Institute who was also representing West Virginia on the workgroup, said that his state’s goal is to add 10 acres of canopy in its portion of the watershed, adding, “It’s difficult for us to just hold the line right now.”
In that eight-county portion of West Virginia, the population has been growing by 50 percent every decade. Rodgers said swaths of trees have recently been cleared for new transmission lines and highways to convey commuters to Washington, DC.
That development comes with a silver lining for tree planters. Municipalities are required to deal with their stormwater runoff. Trees are one of the tools they can use. Unlike in a rural setting, where trees closest to the stream provide the best filtration, the entire tree canopy helps filter runoff that ends up in a stormwater system. Here, every tree counts.
Keith Cline, director of the Urban Forest Management Division of Fairfax County, VA, said that he views new stormwater requirements as key to growing the urban tree canopy. Landowners required to filter the water coming off their properties often turn to trees, one of the least expensive retrofits.
“We are most involved in linking stormwater goals to increasing urban tree canopy,” Cline said, referring to how to get more trees on the ground. “That’s the driving force right now.”
To follow the efforts of the Forestry Workgroup and the progress of the strategy, visit: www.chesapeakebay.net/managementstrategies/strategy/tree_canopy.
To view a draft of the Urban Tree Canopy Management Strategy, visit www.chesapeakebay.net/channel_files/22452/urban_tree_canopy_management_strategy_-_draft_1-28-15.pdf.