Case Study: Glenn Martin National Wildlife Refuge

Name of the wetland

Glenn Martin National Wildlife Refuge, Maryland, U.S.A.

Name of the respondent

Bill Morgante and Steffanie Munguia

What you have seen in the wetland – state, change, and drivers

Current state: Glenn Martin National Wildlife Refuge is a 4,423 acre (1,790 ha) complex of wetland islands in the Chesapeake Bay 6 miles (9.6 km) off the coast of Crisfield, Maryland at the northern end of Smith Island. Martin NWR combines extensive undisturbed shallow-water habitat, SAV, tidal mudflat, and miles of fringing marsh edge. Much of the reserve is dominated by intertidal salt marsh plant communities. The most prevalent emergent species is black needlerush (Juncus roemerianus), though smooth cordgrass (Spartina alterniflora), saltmeadow hay (Spartina patens), and salt grass (Distichlis spicata) are not uncommon. Two species of submerged aquatic vegetation (SAV), eelgrass (Zostera marina) and widgeongrass (Ruppia maritima) dominate the surrounding shallow waters.

Great egret nesting habitat in Glenn Martin National Wildlife Refuge. Photo: U.S. Fish and Wildlife Service.

Each refuge habitat provides important wintering forage for a variety of waterfowl and many wetland dependent mammals. Black ducks (Anas rubripes), and to a lesser extent mallards (Anas platyrhynchos), are common nesting species on the refuge. Additionally, American wigeon (Anas americana), pintail (Anas acuta), gadwall (Anas strepera), Canada goose (Branta canadensis), canvasback (Aythya valisineria), redhead (Aythya americana), bufflehead (Bucephala albeola), black scoter (Melanitta nigra), surf scoter (Melanitta perspicillata), long-tailed duck (Clangula hyemalis), brant (Branta bernicla) and tundra swan (Cygnus columbianus) also nest during the non-breeding season. Nesting raptors include northern harrier (Circus cyaneus), osprey (Pandion haliaetus), barn owl (Tyto alba), peregrine falcon (Falco peregrinus), and bald eagle (Haliaeetus leucocephalus). The refuge supports many wetland dependent mammal species including muskrat (Ondatra zibethicus), mink (Mustela vison), and river otter (Lutra canadensis). The diamondback terrapin (Malaclemys terrapin), northern water snake (Natrix sipedon), and rough green snake (Opheodrys aestivus) are common reptiles — the most vulnerable is the threatened diamondback terrapin.

Change: Chesapeake Bay wetlands are unable to build elevation at a sufficient rate to keep up with Sea Level Rise and subsidence. The Sea Level Affecting Marshes Model (SLAMM) 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. Between 1942 and 2013, the Martin NWR shoreline eroded between 0.6 and 5.5 meters per year, depending on shoreline position. During this timeframe, approximately 237 acres (96 ha) of tidal marsh was lost to erosion. This is a rate of 3.2 acres (1.3 ha) per year. This rapid loss led to the implementation of a recent living shoreline project at Fog Point in the NWR to bolster ecosystem-based coastal protection (Division of Public Affairs 2016). The U.S. Army Corps of Engineers completed this marsh restoration project in the Martin NWR to combat marsh loss with the outcome under close monitoring by NOAA.

Drivers: The most immediate threat to Martin NWR is shoreline erosion. The Chesapeake Bay has double the global rate of sea-level rise due to regional subsidence ( Relative sea level rise, based on tide gauges not separating absolute sea level from subsidence, is 3.44 + 0.49 mm/yr. for nearby Cambridge, MD (Boon et al. 2010).

Marsh at Glenn Martin National Wildlife Refuge. Photo: U.S. Fish & Wildlife Service.

Why you took part

To contribute to this important inventory of international wetlands.

What you hope will come from the survey

International inventory of valuable wetlands with actionable measures governments and others can follow to conserve and perhaps enhance these valuable wetlands.