Forests, Urban Tree Canopy Still Shrinking In Chesapeake Bay Region

ANNAPOLIS, Md. – It’s getting still harder to see either the forest or the trees. New data indicates that the Chesapeake Bay watershed has continued to lose significant amounts of tree canopy and forest as runoff-inducing pavement and buildings keep spreading.

High-resolution aerial surveys show a loss of tree cover nearly equivalent to acreage of Lynchburg, VA, from 2013 to 2021. Meanwhile, over that same time, development covered an area twice the land size of Baltimore, with roads, rooftops, parking lots and other impervious surfaces.

The aerial surveys are part of a federally funded effort to map and track changes in land use and land cover across the Bay watershed. Collaborators on the project include the U.S. Geological Survey, U.S. Forest Service, University of Vermont and the Chesapeake Conservancy. Conducted every four years, the surveys use imaging technology that can identify landscape features to a one-square-meter resolution.

Data from the surveys, recently released by the state-federal Chesapeake Bay Program, highlight shortcomings in the long-running effort to address the harm that development is causing to the Bay and its tributaries.

Trees provide many benefits to the Bay watershed and its occupants. They help clean the air, filtering out harmful particulate pollution and consuming climate-warming carbon dioxide. They reduce stormwater pollution and help control flooding by soaking up rainfall. They reduce erosion, and they provide cooling shade to streams and communities. They provide food and habitat for birds and other wildlife.

Planting trees is widely considered one of the most cost-effective practices for reducing runoff of water-fouling nitrogen, phosphorus and sediment, whether from farm fields and pastures or streets and suburban lawns.

If measured in cost savings or damage avoided, the dollar value of these benefits is substantial: more than $15.3 billion across the entire Chesapeake watershed, according to the Bay Program.

Impervious surfaces, on the other hand, are widely recognized as killers of water quality and aquatic life. When rain falls on roads, rooftops and sidewalks, it runs off and carries pollutants like excess fertilizer, pet waste, toxic chemicals and litter to the nearest waterway. Those hard surfaces also absorb the sun’s radiation, heating stormwater runoff and raising stream temperatures — often to a degree that many fish, amphibians and aquatic insects can no longer live there.

The aerial survey shows that the amount of the Bay’s watershed covered by impervious surfaces expanded by 13,226 acres, or 20 square miles, every year from 2013 through 2021.

Pavement and buildings have long been covering the Bay watershed faster than its population has been growing. From 1990 to 2007, according to the Bay Program, impervious surfaces associated with single-family homes increased by about 34% while the population increased by 18%.

In the agreement, the watershed’s six states and the District of Columbia also committed to restore 900 miles per year of streamside forests and conserve existing wooded shorelines until at least 70% of all riparian areas are forested.

From 2013 to 2021, though, the aerial surveys show that nearly 29,000 acres of tree canopy were lost to development in the watershed’s more populated communities.

Virginia and Maryland accounted for the bulk of those losses. Both of the states separately experienced a nearly 12,000-acre net decline in tree canopy over the eight-year period, according to Bay Program data.

Tree canopy loss was not limited to densely populated areas. Across the entire watershed, from cities to farm country, canopy declines totaled nearly 105,000 acres.

Since the last aerial surveys, tree planting in densely settled areas has picked up. The Bay states and the District of Columbia reported covering 5,743 acres with saplings in 2024, according to the Bay Program. That’s twice the area planted in 2023 and the most in a decade.

In all, about 17,000 acres of trees have been planted in watershed communities since 2014, with Maryland accounting for nearly 60%, followed by Pennsylvania and Virginia.

“These trees will be critical to provide clean water, shade, air and recreational opportunities for local communities throughout the watershed,” said Katherine Brownson, Bay Program liaison for the U.S. Forest Service.

Pennsylvania and Maryland have launched ambitious tree planting campaigns in recent years. The Keystone 10 Million Trees Partnership, a collaboration of government, nonprofits and businesses in Pennsylvania, begun in 2018, says it has put 8.7 million trees in the ground statewide, many of them along streams and rivers, in urban areas and on abandoned mine land.

Maryland set out in 2021 to plant 5 million trees on public and private lands by 2031, with 10% in underserved urban areas. As of mid-April, nearly 1.2 million trees had been planted, with nearly 66,000 in underserved neighborhoods.

Some communities, though not many, have managed to boost tree canopy. Salisbury, MD, tops the list, with about 36% of its land covered by trees, having added 31 acres through 2021.

Charles Stegman, past president of the Wicomico Environmental Trust, credits an environmentally conscious city administration at that time, which commissioned a tree canopy study and a grant program that has enabled the city and groups like Stegman’s to do several mostly small-scale plantings. Salisbury has been recognized for several years in a row as a “Tree City” by the Arbor Day Foundation.

The city got $400,000 from a settlement last year of an air pollution case against Perdue, which it will use to restore and enhance its canopy. Earlier this year, it also received nearly $150,000 from the Chesapeake Bay Trust to plant more than 800 trees. Nick Voitiuc, Salisbury’s director of infrastructure and development, said the challenge is to figure out where to plant them all.

Plantings aren’t enough But planting new trees hasn’t been enough so far to stem losses in the vast majority of places. Three Maryland counties — Anne Arundel, Howard and Frederick — adopted ordinances in 2019 and 2020 aimed at tightening protections for woodlands and requiring replacement of those bulldozed for development. Those changes evidently came too late to show up in the latest aerial surveys.

Even Takoma Park, MD, which for decades has had some of the strongest protections for trees in the Bay watershed, lost about 56 acres of canopy in the eight-year survey period.

Forests provide the same environmental and quality of life benefits that trees do, but in concentration and on a larger scale. The watersheds of healthy streams are usually more than 60% forested, according to the Bay Program. A Maryland assessment found that watersheds where temperature-sensitive brook trout could be found were 70% forested on average.

Keeping track of the watershed’s forests has proven tricky, complicated by the often-temporary losses of tracts harvested for wood products. The aerial surveys identified losses of more than 500,000 acres of forest across the watershed from 2013 to 2021. But timber harvests accounted for most of that, and while some woods may be cleared for housing, commercial development or solar energy projects, many are either replanted or allowed to regenerate naturally.

Even so, the surveys tallied a net loss to development of nearly 103,000 forested acres, according to Peter Claggett, a research geographer with the U.S. Geological Survey who helped analyze the data.

Riparian forests are of particular importance because they buffer streams and rivers from the water-fouling nutrients and sediment washed off the land by rainfall.

The Bay Program has long recognized the importance of riparian forests, but restoring or even preserving them has proven difficult.

Pennsylvania, Virginia and West Virginia already have trees buffering more than 70% of their waterways, according to the Bay Program. The other states are short of the target, and so is the Bay watershed as a whole — though just barely, with 69.96% of shorelines forested.

But the momentum is going in the wrong direction. Since the initial aerial surveys in 2013-2014, the region has seen a net loss of nearly 42,000 acres of streamside forests, according to Bay Program data. Only the District of Columbia shows a net gain — of just three acres.

Efforts to reverse the decline are coming up short. The states have never come close to their goal of restoring 900 miles of riparian forest annually. Only twice, in 2016 and 2023, did they plant more than 600 miles. But in 2024, the pace fell back to 227 miles.

State and federal leaders who guide the Bay cleanup are now mulling revisions to the 2014 pact that would raise the goals that couldn’t be reached. The draft agreement released in July calls for reducing the loss of tree canopy and for planting and maintaining 35,000 acres of community trees by 2035. It calls for planting and maintaining 7,500 acres of new riparian buffers annually, with a goal of increasing streamside forest coverage to 71% of the watershed in the next decade.

As for forests in general, the pact proposes to reduce the loss of woodlands to development “through planning and conservation.” It calls for planting and maintaining new forests by 2035 “to achieve a net gain … over the long term,” but leaves blank the specific amount.

Environmentalists contend that the plan needs to be more specific and ambitious. The Chesapeake Bay Foundation has called for permanently protecting nearly 1.9 million acres of forest, with 8.5% of it bordering streams and rivers. It also recommended striving for a net gain in forests by reducing their loss to development by one third.

The rate of increase grew slightly over that period. The end result: more than 100,000 acres, or about 160 square miles, of pavement and hard structures added to the landscape. That’s twice the 80-square-mile area occupied by Baltimore — or almost enough to cover Richmond, Norfolk and Hampton, VA, combined.

While the harmful effects of impervious surfaces are widely recognized, the 2014 Bay Agreement pledged only to “evaluate policy options, incentives and planning tools” that could curb farmland and forest loss and reduce the spread of impervious surfaces.

The Bay Program is developing an impervious surface “indicator” to more closely track the spread of pavement and buildings. But the proposed revision of the watershed agreement still talks generally of providing land use information and advice without setting goals for limiting or reducing impervious surfaces.

Keisha Sedlacek, senior policy director for the Chesapeake Bay Foundation, said the Bay Program struggles with making specific commitments to limit the spread of pavement and to protect trees and forests because those are land use issues.

“Land use is such a hard issue to dictate from the federal government and most of the time from state government, because it is so local in nature,” she said. “It’s really hard for the [state-federal] partnership to do more than ‘coordinate and share’ when it comes to their land use outcomes and targets.”

Even so, she said, “We can be doing that in a better way.” Especially with losses of trees outpacing new plantings, she added, “We clearly have a problem that we need to start figuring out how to better address.”

*Portions of these places are not in the Bay watershed.