News that Baltimore’s tree canopy has expanded from 27 percent to 28 percent is wonderful. But the target is 40 percent, and if we don’t protect our forest patches, we will lose this modest gain.

Recent news that Baltimore's tree canopy — the proportion of the city shaded by trees — has expanded from 27 percent to 28 percent is wonderful, and is thanks to the dedicated work of TreeBaltimore and its partners. But the target is 40 percent, and if we don't take steps to protect our forest patches from development and the harm caused by invasive plants, we will lose this modest gain.

Since 2012, when Baltimore Green Space and our partners started researching Baltimore's forest patches outside parks, which account for up to 20 percent of Baltimore's tree canopy, we've had the opportunity to correct a number of assumptions — from residents, policymakers and funders — about the woods in Baltimore.


The facts about our forest patches have even surprised foresters. Here's why:

They told us that urban soils are all compacted. In fact, our study of 22 Baltimore forest patches showed that the soils' bulk density and organic matter are comparable to those of rural forests. This matters because forest is the land that best filters stormwater — in the city and elsewhere.

Baltimore's tree canopy covered 28 percent of the city in 2015, 1 percentage point more than it did in 2007, according to the U.S. Forest Service and University of Vermont.

They expected many invasive trees. In fact, in the forest patches we surveyed, upward of 80 percent of the canopy trees are native species, such as oaks, maples, tulip poplar and sassafras. Local wildlife depend on these trees, which are also a part of our Maryland heritage. Many of these trees grow very large — the biggest we've found is 56 inches in diameter at breast height — which makes them far more effective at filtering stormwater and cleaning the air. For example, while a 10-inch red maple intercepts 1,565 gallons of water per year, a 20-inch red maple intercepts 5,926 gallons, and a 30-inch red maple intercepts 11,263 gallons.

They were surprised to see native plants growing on our forest floors, as invasive species stifling forest regeneration is a problem in most forest patches. Baltimore's forest patches also have native species on their floors, however, such as mayapples, pink lady slipper orchid and lowbush blueberry. In contrast, in areas that have more deer such as Baltimore County, forest floors are nearly bare, and seedlings cannot survive without intensive management.

They didn't expect forest specialist birds. These are birds that were thought to require substantial forest interior; a guideline is a 50-acre forest with at least 10 acres of interior. Yet, forest specialists — including Acadian flycatcher and vireos — have been spotted in Baltimore's forest patches, which are far smaller. Baltimore's forest patches provide needed habitat for at least 90 bird species.

They assumed that the neighborhoods with greenery and with environmentalists are richer and whiter. In fact, forest patches are as common in areas that Baltimore City denotes as "distressed" and "middle market stressed" housing markets as in better-resourced areas. And more than half of the most active forest stewards Baltimore Green Space works with are people of color. Forest patches are accessible to and valued by a spectrum of Baltimoreans.

Despite daunting challenges, Baltimore must aggressively expand and maintain its urban forest

In partnership with the USDA Forest Service, Baltimore Green Space is engaging residents and city and state agencies to identify how forest patches contribute to Baltimore. We're looking at the things neighbors commonly speak of, such as the birds and large trees, breathing clean air and contact with nature. We're also looking at municipal goals such as reducing stormwater runoff, reducing the urban heat island effect, cleaning the air to reduce respiratory illness, and mitigating the effects of climate change.

Despite all the value they provide, protections for forested land in Baltimore are minimal; municipal and individual action is needed. It's time to update Baltimore City's Forest Conservation Program to reflect the benefits of the smaller forest patches found in the city. Baltimore also should join the ranks of cities like Annapolis and Atlanta that have tree ordinances. And finally, the value of forest patches and their need for maintenance must be recognized by programs to clean up the Chesapeake Bay. The forests need our help, and we need theirs.

Katie Lautar (katherine@baltimoregreenspace.org) is the program director and Miriam Avins (miriam@baltimoregreenspace.org) is the executive director at Baltimore Green Space. The organization will convene forest stewards, scientists and policy makers Nov. 9 to strategize about how to protect the woods. For information, write to info@baltimoregreenspace.org.