Northern Virginia, as part of regional approach, adopts goal of maintaining 50% tree canopy

The Washington D.C. area has seen tree canopy decline from over 50% to just under that amount in less than a decade, according to the regional government authority. 

Officials with the Metropolitan Washington Council of Governments, which includes Northern Virginia jurisdictions, voted last week to set a goal of maintaining at least that 50% amount.

“There’s a lot of things that are unpredictable,” said Michael Knapp, MWCOG regional tree canopy subcommittee chair and tree specialist with the Montgomery County Department of Permitting Services. “We feel that the 50% is attainable and realistic based on current conditions.”

The goal, which jurisdictional members may act on voluntarily, comes after the MWCOG in 2020 adopted its climate and energy action plan, which includes planning for urban tree canopy adoption to achieve the region’s climate and energy goals.

The recent tree canopy goal is also the culmination of years of work to produce a report that found the region in 2014 had 51.3% of land covered by tree canopy. In 2023, that number decreased, spurred by  development and other reasons, to an estimated 49.6%, a trend that, if it continues, would result in about 44.4% of tree coverage by 2050.

“The idea is to use trees and forests as a means of improving the quality of life and environmental health in the region by optimizing the services and benefits they provide,” Knapp said in a phone interview. “In order to sustain the same level of environmental help, you would either have to put money into man-made technologies that provide those types of services and benefits, or experience a decline in environmental health and economic vitality”

Trees have been proven to contribute numerous benefits to the environment, from reducing stormwater pollution runoff and sediment erosion, to capturing carbon and mitigating heat islands.

The report used information from the Chesapeake Bay Program model years 2014 and 2018, which identifies tree canopy as a way to meet pollution reduction goals. More recent Bay Program data is being finalized for next year. MWCOG also used satellite imagery to determine the percentage of tree canopy within a locality.

In terms of acreage, the largest loss in Virginia happened in Loudoun County, with about 2,800 acres swallowed up primarily by home development, Knapp said. The region has also seen an increase in data center development, which Knapp said comes after the region had branded itself as a tech corridor and home to former internet provider powerhouse AOL.

But because of land being converted to housing, Loudoun County has an opportunity to make gains in canopy because of Virginia tree ordinances that require builders to replace trees lost during the home building process, Knapp said, as opposed to land being developed for commercial industry uses.

Arlington and Alexandria made gains on tree cover, adding 7.6 acres and 18.8 acres, respectively. Knapp said the increases are likely due to trees planted under those localities’ regulations coming to bear, Knapp said. Those levels are expected to remain stable given the amount of development that occurs on a yearly basis, he added.

The largest canopy increase was Frederick County, Maryland, with about 2,100 acres, which Knapp surmised benefited from a phenomenon known as “pioneer forests.” 

Frederick County, similar to more rural Loudoun and Prince William counties in Virginia, has land that originally was set aside for agricultural purposes, but had been converted to developed land in recent years. If there were economic difficulties that delayed development, the land may have been untouched for years before being built on and trees sprouted during the wait, leading to the canopy now getting picked up by the satellite imagery. 

This represents an opportunity to pick up some tree canopy as development occurs, similar to what happened in Northern Virginia, which was one of the top dairy producers in the state in the 1950s before it became developed into the bedroom community that it is, Knapp added. Fairfax County had tree conservation and stream valley preservation ordinances they could use.

“As those areas were developed, some of those pioneers were given the chance to develop and mature,” said Knapp.

The 104-page report from MWCOG outlines the costs offset by maintaining tree canopy and offers guidance for preserving trees that may be more susceptible to die from diseases or increased moisture from heavy rain.

“There’s just a lot of outreach and public education that local governments can do,” Knapp said. “They need to instill a sense of ownership in the community. Local governments cannot do this on their own.”

One counter argument to tree preservation requirements is the reduction of the number of houses that can be built on a lot, thereby reducing the housing stock size and increasing housing costs.

Andrew Clark, vice president of government relations with the Home Builders Association of Virginia, said in a previous interview: “Developers will find a way to make these ordinances work, but it may undercut localities’ objective to provide an array of housing. That’s just kind of a trade-off.”

Bills to preserve trees during home building awaiting action from governor

But Knapp said a provision in Virginia statute allows for deviations to be made if allowed densities can’t be met, and stakeholders that worked on Virginia’s tree conservation law in 2007 had reached consensus by creating a cooperative process between the two perspectives. The trees, Knapp said, can be a marketing tool for prospective tenants who have come to desire them, which the home builders acknowledged. 

“If you just planned for trees when you’re doing your development you won’t sacrifice your houses,” added Brian LeCouteur, MWCOG principal environmental planner and regional urban forester. 

And whereas putting homes on farmland may cost less than cutting forestland, if developers plan to use forestland, which “just happens,” LeCouteur said, it can be less costly to preserve existing trees instead of needing to plant new pens.

“We’re not trying to pit agriculture against silviculture,” said LeCouteur. “The idea is to just put [trees] in the plan.”

Recently, Republican Gov. Glenn Youngkin vetoed bills that would’ve made Northern Virginia’s tree conservation process during homebuilding an option statewide. Another bill would’ve made some localities’ existing requirement to replace trees lost through homebuilding available to towns, cities and counties across the commonwealth. 

“The fact that the bills made it out of the House of Delegates and the Senate to the governor’s desk is quite the achievement,” LeCouteur said. “I have a strong [sense they] will eventually make it to a governor’s desk in the coming years. People are definitely aware of these now, and realize how important trees are to our environment.”

The Potomac River Conservancy, which backed those bills this session, supports MWCOG’s tree-boosting goal, as does the Chesapeake Bay Foundation. 

“Increased tree canopy goals and affordable housing don’t have to be mutually exclusive,” said Anna Mudd, senior director of policy at the Potomac River Conservancy, in a statement. “We look forward to continuing to work with all stakeholders to develop creative and equitable solutions that ensure that everyone in the Potomac River region has the opportunity to live in communities with clean air, clean water, and access to green spaces.”