By Jared Parks, Director of Land Programs, Lower Shore Land Trust
To fully appreciate the challenges that our Atlantic and Chesapeake Bay salt marshes are facing, it is essential to understand how factors such as flooding and elevation create the unique zones found within a typical salt marsh. Though small, these differences lead to very distinct differences in what plant and animal communities each zone can support. Marshes are described by separate zones based on the small elevation rise from the edge of the water to the edge of dry land; “low marsh,” “high marsh,” “pannes” (high salt, low vegetation areas), “hummocks” (taller bumps that rise above the overall marsh platform), and marsh/land border.
Aerial photo illustrating the transition from low marsh (dark brown vegetation) to high marsh (light green vegetation) to upland forest (darker green vegetation). Photo credit: Larisa Prezioso, Eastern Shore Land Conservancy
Low Marsh Zone
The “low marsh” is flooded twice a day by the normal tidal cycle. As such, the low marsh is a haven for many species of aquatic life such as blue crabs, small fish, and shellfish. The main vegetation is Spartina alterniflora, or cordgrass, which is a vigorous plant that helps make the low marsh one of the most productive ecosystems in the world. Due to the regular flooding, this zone is not suitable for species like the saltmarsh sparrow that nest very low to the ground.
Blue crab in low marsh zone. Photo credit: Brian Henderson.
High Marsh Zone
The focal zone of “Marshes for Tomorrow” is the “high marsh” and its unique assemblage of organisms, particularly the saltmarsh sparrow (Ammospiza caudacuta). Unlike the low marsh, the high marsh is not flooded by daily tides during the summer months making it an ideal location for the saltmarsh sparrow to nest. The high marsh zone is particularly susceptible to storm surges and sea level rise because it falls only a few inches in elevation above the low marsh. Based on statistical computer models, Maryland is predicted to lose a larger proportion of this high marsh zone than the low marsh. With increased flooding and high marsh loss, we see a corresponding decrease in successful breeding attempts by Saltmarsh Sparrow. This loss is a key driver of our restoration planning effort for the lower Eastern Shore’s salt marshes.
Saltmarsh Sparrow chicks in a nest in the high marsh zone. Photo credit: Lauren Owens Lambert, USFWS
Here on the Delmarva, the tidal range is very narrow (only a couple of feet), and the marsh is very flat, with only a small change in elevation from the shoreline to the upland. The topography and tidal regime in our region has created these large expanses of marsh, but it also makes it more difficult for the marsh to adapt with sea level rise.
Marsh migration is the process through which marsh can begin to move inland if unobstructed, as sea level rises and flooding frequency increases. As the water rises, the low marsh will begin to displace the high marsh, but, in most cases, the high marsh will not be able to migrate inland due to obstacles such as roads and buildings. This is playing out right now in mid-Atlantic marshes, and it is creating serious problems for the saltmarsh sparrow, which has lost nearly 90% of its total population since the late 1990’s.
Marshes for Tomorrow (MfT) is an ambitious project led by Audubon mid-Atlantic and regional partners of the Delmarva Restoration and Conservation Network (DRCN) to identify, protect, and restore at least 25,000 acres of the most important tidal salt marsh habitat on Maryland’s Eastern Shore for Saltmarsh Sparrows. MfT is utilizing the most recent scientific analysis coupled with community input to select the areas to concentrate our efforts. If you would like to learn more about MfT or join one of our upcoming public meetings, please visit the MfT website at https://www.delmarvarcn.org/marshesfortomorrow.
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