Photo: A view of Dyke Marsh, Dixie Sommers
Glenda C. Booth, President, Friends of Dyke Marsh
Juvenile Bald Eagle bathing at Dyke Marsh, Dixie Sommers
Experienced and novice birders alike have had “front-row seats” this year in the Dyke Marsh Wildlife Preserve, observing both an Osprey and a Bald Eagle pair raising their young. The Ospreys had two young at an easily-viewed nest on a platform just off the Belle Haven Marina boat ramp. Sadly, one of the chicks did not survive. The Bald Eagle pair raised three young at a very visible nest along the Haul Road Trail. The birds’ fans started seeing the eagles bringing sticks to the nest as early as December. These are just two examples of birds in the preserve. Cornell’s eBird lists Dyke Marsh as a birding hotspot with 271 species reported.
The Dyke Marsh Wildlife Preserve, in northern Mount Vernon along the Potomac River shoreline, is the "nearest thing to primeval wilderness" in the Washington area, wrote Louis J. Halle in 1947 when he biked from the city at dawn to watch the wetland awaken.
Congress’s intent in adding it to the national park system in 1959 is clear: “so that fish and wildlife development and their preservation as wetland wildlife habitat shall be paramount.” Dyke Marsh is a unit of the George Washington Memorial Parkway managed by the National Park Service (NPS).
Black Swallowtail butterfly on Cardinal Flower, Dixie Sommers
It is one of largest remaining tidal, freshwater marshes in the Washington area and one of largest tidal, freshwater, temperate, climax, riverine, narrow-leafed cattail marshes in the NPS system. Part of the marsh is at least 2,200 years old.
According to NPS data, its tidal wetland, swamp forest, floodplain forest and open water provide habitat for over 230 known species of birds, 300 plants, 6,000 arthropods, 38 fish, 16 reptiles, 14 amphibians and 26 mammals, the latter including exotics like feral cats. Wetlands are “biological supermarkets,” notes Kirk Havens with the Virginia Institute of Marine Science.
Marshes Unappreciated
Many wetlands, tidal and nontidal, have been sacrificed – filled and paved over – for roads, buildings and other development. For much of U.S. history, people viewed wetlands as mosquito-ridden dumping grounds to avoid. Some names were telling. In the 1800s, Dyke Marsh was called “Hell Hole,” and William Byrd named the wetland in eastern Virginia the Great Dismal Swamp. On an intriguing side note, during prohibition, Dyke Marsh was a hideout for bootleggers. Clandestine, enterprising purveyors could conduct their business in the dense vegetation and along the river, where state and federal jurisdictional lines were blurred.
Dyke Marsh has endured years of excavation, dumping, pollution, invasive plants and animals, poaching, illegal bow fishing, hunting, polluted runoff, off-leash dogs and endless trash.
Eastern Kingbird nesting, Dixie Sommers
Six species of birds that breed in Dyke Marsh are on Virginia’s list of Species of Greatest Conservation Need: Black and White Warbler, Brown Thrasher, Eastern Kingbird, Gray Catbird, Green Heron and Least Bittern.
And while it is a favorite place to watch birds and other wildlife, Dyke Marsh is much more than birds. It provides ecological services, including flood control, storm buffering, water quality enhancement, biodiversity, carbon sequestration and shoreline stabilization.
Saving Dyke Marsh
Over half of Dyke Marsh was hauled away by dredgers from 1940 to 1972, which destabilized the whole hydrologic system, two U.S. Geological Survey (USGS) studies concluded. USGS reported that in 1940, the wetland part of the preserve was around 180 acres. By 2010, it was around 53 acres. The dredging that removed around 101 acres or 54 percent of the 1937 marsh was a strong destabilizing force, transforming it from a net depositional state to a net erosional state.
In 2010 and 2013, the USGS concluded that Dyke Marsh was eroding six to eight feet or 1.5 to two acres per year a year on average and at an accelerating rate. They predicted that at this rate Dyke Marsh would be gone by 2035.
Said USGS: “Analysis of field evidence, aerial photography, and published maps has revealed an accelerating rate of erosion and marsh loss at Dyke Marsh, which now appears to put at risk the short-term survivability of this marsh.”
NSP prepared a restoration plan and, with the help of the Friends of Dyke Marsh (FODM or the Friends) and other organizations, received over $25 million to stabilize the marsh. In 2013, then Interior Secretary Sally Jewell came to the marsh to announce the funding and a restoration-stabilization plan. In 2020, NPS completed phase one, construction of a breakwater that replicates a former promontory that protected the marsh. USGS identified the breakwater as a priority that would “redirect erosive flows in the marsh, particularly during strong storms and re-establish hydrologic conditions that would encourage sediment accretion.” In 2022, NPS’s contractor completed four sills north of the breakwater to also help stem erosion and encourage accretion.
FODM Projects
Another restoration effort is underway as well. Many of the upland areas of the marsh, especially along the trails, are overrun with invasive plants, like much of northern Virginia’s habitat. FODM teams work twice a month to control invasive plants near the Haul Road Trail, where most people visit the marsh. In June, FODM recently received a Dominion Energy Charitable Foundation grant to control three plots infested with mile-a-minute, porcelain berry, English ivy and other non-native plants. In one area in 2018, after clearing invasive plants, volunteers and NPS staff planted over 4,000 native trees and plants. NVBA helped fund the purchase of the plants.
The Friends have several other projects:
breeding bird, butterfly, dragonfly and plant surveys;
treatment of 20 pumpkin ash trees to combat the invasive emerald ash borer;
a wildlife monitoring camera;
planting black willow stakes to stabilize the marsh;
guided walks focused on birds every Sunday;
other periodic walks focused on butterflies, trees, ecology and plants’ fall colors;
trash cleanups;
water testing;
annual raptor event;
advocating for national parks, clean water and other issues; and
public meetings with speakers on conservation topics.
Dyke Marsh like many natural areas offer what Henry David Thoreau called “the tonic of wildness.” The best way to really see Dyke Marsh is in a kayak or canoe. We hope you will visit and try nature’s restorative elixir. We invite you to join the Friends of Dyke Marsh by visiting our website, where you also can find more information about the marsh and a printable bird checklist.
Fall color at Dyke Marsh, Dixie Sommers