Glenn Martin National Wildlife Refuge
Glenn Martin National Wildlife Refuge (Martin NWR) is a 4,423 acre complex of wetland islands in the Chesapeake Bay 6 miles off the coast of Crisfield, MD at the northern end of Smith Island, Somerset County, MD.
Martin NWR combines extensive undisturbed shallow-water habitats, SAV beds, tidal mudflats, and miles of fringing marsh edge. Each of these habitats provides important wintering forage for a variety of waterfowl. Collectively, they make the refuge an important area for a variety of migratory waterfowl. In late summer, the adult diamondback terrapin generally inhabits the deep portions of creeks and tributaries, avoiding nearshore waters. Juvenile terrapins inhabit shallow creeks and coves adjacent to salt marshes as nursery areas. During June and July, female terrapins cross the intertidal zone and seek nest sites in open sandy areas, particularly in the protected coves of Martin NWR.
Exemplary Ecosystem Services
Maintains ecological connectivity/cohesion
Aesthetic/Cultural Heritage Value/Provisioning
Recreation (birdwatching, ecotourism)
Water quality improvement
Conservation Status and Threats
Conservation statusFederal Protection Sea level rise and erosion are the greatest threats to Martin. See "Other Information" below.
Adjacent land useHerbaceous Wetland
Approximate natural buffer width> 100 ft
Martin NWR combines extensive undisturbed shallow-water habitats, SAV beds, tidal mudflats, and miles of fringing marsh edge. Each of these habitats provides important wintering forage for a variety of waterfowl. Collectively, they make the refuge an important area for a variety of migratory waterfowl. Black ducks (Anas rubripes), and to a lesser extent mallards (A. platyrhynchos), are common nesting species on the refuge. Additionally, American wigeon (Anas americana), pintail (A. acuta), gadwall (A. strepera), Canada goose (Branta canadensis), canvasback (Aythya valisineria), redhead (Aythya americana), bufflehead (Bucephala albeola), black scoter (Melanitta nigra), surf scoter (M. perspicillata), long-tailed duck (Clangula hyemalis), brant (Branta bernicla) and tundra swan (Cygnus columbianus) join the nesting species during the non-breeding season. Nesting species of raptors include northern harrier (Circus cyaneus), osprey (Pandion haliaetus), barn owl (Tyto alba), peregrine falcon (Falco peregrinus), and bald eagle (Haliaeetus leucocephalus). Two nesting towers were constructed for peregrine falcon on the refuge. These towers were constructed in the 1980s to support recovery efforts for the species. The tower near Lighting Knot Cove has not been used in many years, but the Anderson Creek tower is still in use. The extensive wetland habitats on the refuge support many wetland dependent mammal species such as muskrat (Ondatra zibethicus), mink (Mustela vison), and river otters (Lutra canadensis). Red fox (Vulpes vulpes) and raccoons (Procyon lotor) are also common mammals. Martin NWR is notably free of nutria (Myocastor coypus), an invasive species that has caused extensive damage to other marshes on the Eastern Shore of Maryland. As a result, the marsh on the refuge is in better health than many comparable marshes on the mainland. The diamondback terrapin (Malaclemys terrapin), northern water snake (Natrix sipedon), and rough green snake (Opheodrys aestivus) are common species of reptile found on Martin NWR . Of these species, the most vulnerable is the diamondback terrapin, which inhabits salt and brackish water within the tidal marshes and creeks of the refuge. In late summer, the adult diamondback terrapin generally inhabits the deep portions of creeks and tributaries, avoiding nearshore waters. Juvenile terrapins inhabit shallow creeks and coves adjacent to salt marshes as nursery areas. During June and July, female terrapins cross the intertidal zone and seek nest sites in open sandy areas, particularly in the protected coves of Martin NWR.
Although marshes build elevation over time, primarily through plant growth, organic matter accumulation, and sediment deposition, many wetlands in the Chesapeake Bay are not able to keep pace with relative sea level rise. Thousands of years ago, Martin NWR and Smith Island were a part of a peninsula that encompassed Tangier Island to the south, and South Marsh and Bloodsworth Islands to the north. Over time, as the water level rose and erosion continued, the peninsula separated into distinct islands. The land itself has steadily changed from dry uplands to wetlands. Smith Island is currently almost all salt marsh and has lost considerable amounts of historic upland habitat, resulting in the loss of the farms that were the primary means of subsistence on the island centuries ago.
Relative sea level rise, based on tide gauges which do not separate absolute sea level from subsidence, is 3.44 + 0.49 mm/yr. for Cambridge, MD (Boon et al. 2010). The rate of sea level rise has increased since the late 19th century and is predicted to accelerate in the future. This will continue to submerge wetlands that are unable to build elevation at a sufficient rate. The Sea Level Affecting Marshes Model (SLAMM) for the area predicts most of Smith Island will convert to open water by 2050. This model is based on the estimate of sea level rising 1.03 meters by 2100. SLAMM accounts for the dominant processes of inundation, erosion, overwash, substrate saturation and vertical accretion involved in wetland conversion and shoreline modification during long-term sea level rise.
The most immediate threat to Martin NWR is shoreline erosion. Between 1942 and 2013, the shoreline on Martin NWR eroded between 2 and 18 feet per year, depending on shoreline position. During this timeframe, approximately 238 acres of tidal marsh has been lost to erosion. This is a rate of 3.3 acres per year.
Approximate size (ha):
General wetland characterization:Coastal Salt Meadow, Coastal Irregularly Flooded Salt Marsh, Coastal Regularly Flooded Salt Marsh
Adjacent water bod(ies)Tidal Systems
Approximate stream order
Name of body of waterChesapeake Bay
The soil survey off the web can only download a zipped shape file.
Flora and Fauna
Dominant floraIntertidal saltmarsh plant communities dominated the study area. The majority of the emergent vegetation is black needlerush (Juncus roemerianus). Other species located within the refuge area are smooth cordgrass (Spartina alterniflora), saltmeadow hay (Spartina patens), salt grass (Distichlis spicata), marsh elder (Iva frutescens), groundsel bush (Baccharis halimifolia), saltmarsh bulrush (Schoenoplectus robustus), waterhemp (Amaranthus cannabinus), and common reed (Phragmites australis).
Unique floraTwo species, eelgrass (Zostera marina) and widgeongrass (Ruppia maritima), are the dominant SAV species of Smith Island and adjacent Tangier Sound. These two species have been recognized by the scientific community and Chesapeake Bay Program as extremely important to the overall ecology of the Chesapeake Bay. Primary production, fisheries habitat, nutrient uptake, wave attenuation, reduction in current velocity and sediment stabilization are just a few functions that SAV provides the Bay.
Dominant faunaShallow waters near Martin NWR are likely to support various species of minnows, killifish, and silversides. Mummichogs (Fundulus heteroclitus) stay close to shore during the warmer months, entering marshes to feed with the tides. Bay anchovies (Anchoa mitchilli) and silversides are some of the most plentiful fishes in the Bay. Needlefish (Strongylura nuvina), as well as larger predatory fishes such as striped bass (Morone saxatilis) and bluefish (Pomatomus saltatrix), prey on these small fish c
Rare faunaThe mix of undisturbed wetlands and scattered uplands provides an ample food supply that makes the refuge an attractive habitat for colonial waterbirds and dozens of migratory bird species. Cherry Island and the Lookout Tower are two of the largest and most diverse wading bird nesting colonies in Maryland. Nesting species include glossy ibis (Plegadis falcinellus), great blue heron (Ardea herodias), great egret (Casmerodius albus), snowy egret (Egretta thula), tricolored heron (Hydranassa trico