Deer Population and Forest Health in the Arlington Region

Too Many Deer?

Are too many deer endangering our local flora and fauna? If so, what can be done about it?
On February 22 at 7 p.m., join a free webinar with a top national expert on deer management, Dr. Bernd Blossey, a professor of natural resources and the environment at Cornell University. The talk is sponsored by ARMN and a network of other Northern Virginia environmental organizations.
Register here for Zoom details

A generation ago, white-tailed deer were a rare sight in the suburban forests of Northern Virginia. Today, it’s no surprise to spot a few browsing in a neighbor’s garden. Beautiful as they are, the deer we often glimpse on the edges of parks and bike trails these days are a sign of an ecosystem out of balance and in decline.

Animated photo courtesy of National Park Service

A single deer eats more than five pounds of shrubs, leaves, nuts, seeds and other vegetation every day. A square mile of healthy forest can support about 15 to 20 deer eating at that clip. Above that, the forest starts to lose its ability to regenerate.

A growing body of evidence indicates that deer populations have crossed that threshold and are endangering the future of forests across the eastern United States, including in the Arlington region.

Especially vulnerable to deer browsing are low-growing native plants that provide food and shelter to insects, birds and other wildlife, leaving “an impoverished environment,” as described by the Virginia Native Plant Society.

Songbirds like the Eastern towhee, wood thrush and brown thrasher can’t build their nests or find food for their young. Mammals and amphibians can’t hide from predators.

Oak saplings – a deer favorite – don’t survive to replace the current generation of canopy trees. And there’s less plant material on the ground to absorb rainfall, allowing excessive runoff into the Chesapeake watershed.

On the left is a relatively undisturbed landscape at Lacey Woods Park, a small urban park surrounded by housing and busy streets, Note the abundance of shrubs and undergrowth. To the right, a photo taken the same day at Long Branch Park off Four Mile Run, where large numbers of browsing deer have cleared most plants they can reach. Photos by Steve Young

Lacking predators to keep their numbers in check, deer in these suburban forests are destined to continue growing in population until stopped by famine or disease. In fact, density is believed to be contributing to the spread of fatal chronic wasting disease (CWD) among deer in at least 24 states, including Virginia.

A future without forests?

Deer overpopulation is recognized as a threat to long-term forest health throughout the eastern states by federal land management agencies including the National Park Service and the U.S. Forest Service.

In 2019, researchers for the Park Service and the University of Maine analyzed seedling data for eastern forests and found a severe deficit of young trees from northern Virginia through Massachusetts. Deer overpopulation, invasive plants, and human land modification were the main causes. Although the impact may not yet be apparent, the diminishment of our forests has already begun.

“A forest can appear viable based on a healthy adult population, while closer examination suggests that the adult population is unlikely to be replaced due to insufficient juveniles (regeneration failure) or different juvenile species composition (regeneration mismatch),” the researchers wrote.

Trees in cages

ARMN members who volunteer to restore natural habitat in our regional public parks have seen firsthand the imbalance caused by too many deer. Our suburban forests are dominated by a few native species that deer don’t find appetizing, like Spicebush and Pawpaws, and lots of harmful exotic invasive plants that deer won’t eat.

Early attempts at habitat restoration were frustrated when overabundant deer devoured the large native plantings. Volunteers have learned to protect native trees and shrubs, typically by surrounding each one with a sturdy deer-proof cage. That is not a sustainable approach for large-scale reforesting.

Native trees planted for habitat restoration in Tuckahoe Park are protected from overpopulated deer by wire cages. Photo by Todd Minners

ARMN helps maintain large deer-proof fenced areas, called exclosures, at three local parks: Gulf Branch and Long Branch nature centers in Arlington and Dora Kelley Nature Park in Alexandria. Over time, the exclosures will provide evidence of the impact of too many deer on the forest floor.

Changing times

Deer numbers in Virginia were once so low, state wildlife officials imported them from nearby states to satisfy hunting needs. For decades, through the 1980s, management efforts focused on keeping the deer population strong.

But that approach took a turn in the 1990s in response to an explosive increase in deer, especially in the suburbs, where deer-friendly landscapes and a lack of predators led populations to spike.

“Today, deer management objectives have changed to control and stabilize populations over much of Virginia,” the state Department of Wildlife Resources explains on its website.

Other jurisdictions along the East Coast have experienced a similar evolution in approach to deer populations – from protection to control and management.

After more than a decade of experimentation with deer control methods on the grounds of Cornell University, researchers there compiled a guide for community-based deer management – a four-step process that results in an action plan. Dozens of communities have used the system; many told their stories here.

Deer management in the region

Local jurisdications in Virginia and Maryland began implementing their own deer management programs in the 1990s in response to degradation of natural habitat as well as traffic accidents and resident complaints.

Most programs use trained civilian hunters and/or public safety sharpshooters to cull deer, using established protocals that ensure the safety of residents. No safety incidents have been reported from these programs.

  • Fairfax County deer management includes archery and gun hunts by civilians as well as police sharpshooting The program operates in 100 parks covering more than 80% of county parkland, It is implemented by police in collaboration with park authorities,
  • Montgomery County deer management is active in 54 parks covering more than half of the county’s total park area. Archery and sharpshooting are deployed in restricted areas. The program is supplemented by private organizations able to hunt on lots as small as 1/5 acre.
  • Arlington County is currently assessesing the need for a deer management program. The county hired a specialist to conduct an aerial survey of its deer population in 2021, which found unhealthy levels of deer in some parklands and recommended “aggressive deer management” to protect native habitat and wildlife. A second contractor is now preparing a proposed plan of action for the County Board to consider sometime in 2023.
  • The National Park Service operates deer management programs in a number of local parks including Rock Creek Park, C&O Canal, Manassas Battlefield, and Catoctin Mountain, The Park Service is now expanding to others parks in DC East area (including Anacostia, Kenilworth, and Fort Washington).
Restoring balance improves forest health

Parks that actively control their deer populations have seen an increase in forest understory and native tree saplings that point to a more sustainable future.

Oak saplings thrive in a section of Lake Fairfax Park, one of about 100 Fairfax parks with deer management programs.

Additional resources

Forest Ecology and Management, February 2020
Effects of culling white-tailed deer on tree regeneration and Microstegium vimineum, an invasive grass.
In Catoctin Mountain Park, tree seedling density increased 11-fold after deer management was introduced.

Washington Post, April 13, 2020
DC’s official bird, the wood thrush, has been disappearing from these parts
The bird is now the “poster child of declining forest songbirds” in part due to deer browsing.

Journal of Applied Ecology, March 2019
Compounding human stressors cause major regeneration debt in over half of eastern US forests
Researchers documented a severe deficit of young trees from northern Virginia through Massachusetts. Deer overpopulation, invasive plants, and human land modification were the main causes.

Ecology and Evolution, November 2019.
Red oak seedlings as indicators of deer browse pressure: Gauging the outcome of different white-tailed deer management approaches, 

National Park Service webpage
Managing Deer Impacts
Long term studies clearly show “that many eastern national parks lack adequate tree regeneration due to decades of over browsing by white-tailed deer.”  With a map showing areas at risk of imminent failure.

Cornell University/The Nature Conservancy
Community-Based Deer Management
A guided process for addressing deer-related problems with examples from communities across the country.

U.S. Forest Service Northern Research Station, 2011
Long-Term Differences in Forests With Different Deer Densities
Thirty years after new forest stands were planted, Forest Service scientists found that tree species diversity, canopy foliage density, insect density and bird density, all decreased significantly as the deer density at stand initiation increased.

Northeastern Naturalist, September 2013.
Effects of Twenty Years of Deer Exclusion on Woody Vegetation at Three Life-History Stages in a Mid-Atlantic Temperate Deciduous Forest 
Tree seedlings inside the protected area were more than twice as tall and four times as plentiful than those outside the exclosure.

U.S. Department of Agriculture, June 2008
Impacts of White-Tailed Deer Overabundance in Forest Ecosystems: An Overview

Virginia Department of Game and Inland Fisheries Deer Management Plan

Full 2021 Arlington County deer survey

Restoring Balance: White-tailed Deer Management in Northern Virginia An ARMN flyer designed to be a double-sided printed document. Set your printer to borderless printing.

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