On the Shore of Salty Soils and Rising Seas

As sea levels rise, the coastal salt marshes of the Delmarva Peninsula are migrating inland. These tidal marshes are usually populated with grasses and other salt tolerant species. Marsh ecosystems are some of the most productive in the world (National Park Service, 2016). An observable trait of marsh migration is the distribution of the invasive perrenial grass, Phragmites australis (Meadows et al., 2007).

While Phragmites australis is native to the Mid-Atlantic region, an aggressive subspecies has become a nuisance for farmers and land owners on the Eastern Shore. It grows in dense patches, and can reach heights of 20 feet tall. With compact stands of the grass occupying the ditches and gullies adjacent to coastal cropland, drainage of the field is reduced. As increasingly salty waters enter areas of higher elevation that were once protected from salinity, Phragmites fills spaces that less salt tolerant plants cannot. Farmers and land owners are forced to spend time and money on the containment and removal of Phragmites, exemplifying a costly impact of sea level rise on the Eastern Shore.

Protecting the American Black Duck Population

Anas rubripes, or the American Black Duck, have recently seen a concerning decline in population. With suitable wetland habitat declining rapidly, and increasing competition from species that fill similar ecological roles, the Black Duck population has not managed to return to original levels after a 50% decline in numbers in the last three decades. Researchers now refer to the American Black Duck as a flagship species, representing how sea level rise jeopardizes the biodiversity of coastal environments. To help American Black Ducks return in full numbers to the eastern United States, the Atlantic Coast Joint Venture (ACJV) region has implemented an extensive conservation plan (ACJV, 2020).

Aims of the Black Duck Conservation Plan:

• Protect Marsh Migration Corridors
• Restore Tidal Wetland Hydrology
• Improve Water Level Management on Managed Wetlands
• Control Exotic and Invasive Species
• Facilitate Marsh Migration

Major Threats to the Black Duck Population

American Black Duck Call (above)

Coastal farmers on the Eastern Shore are affected by saltwater intrusion due to their proximity to the shoreline. Saltwater intrusion disrupts soil composition and traditional crop growth. As saltwater seeps landward, it jeopardizes the delicate balance required for successful cultivation, resulting in diminished yields and financial losses for farmers who rely on cultivable land for their livelihoods. Rick Abend, owner of Abend Hafen Tree Farm, encapsulates the broader struggle farmers face along the Eastern Shore and beyond. His experience highlights the urgent need for sustainable solutions to mitigate saltwater intrusion's adverse effects on agricultural productivity.

While many coastal communities across the Delmarva Peninsula face challenges brought on by sea level rise, Dorchester County exemplifies the situation's urgency. What was once Maryland's 4th largest county by land area will become the 14th largest by 2100. Researchers predict that the Chesapeake Bay will see a 2-foot sea level rise by 2050 and a 5.5-foot rise by 2100. The flat terrain means that a modest rise can reach far inland. The slow and steady process of sea level rise might take time to become apparent. But over time, residents have seen erosion claim shoreline, crops whither from saltwater intrusion, and land become inundated with nuisance flooding. 

Nuisance flooding occurs when high tides, rain, or other weather events cause disturbances to roads and homes but not immediate damage. For example, some towns in Dorchester occasionally schedule school release times to allow buses onto the streets before the tide submerges them. Faster processes like hurricanes and associated storm surges cause immediate damage. These slow and fast processes upend livelihoods and cause communities to rearrange their daily activities. While some of the worst effects of sea level rise will be painfully apparent in the not-so-distant future, residents are already suffering the consequences. 

There is good news, however: sea level rise is not inevitable. Given it is caused by the adverse effects of burning fossil fuels, one solution is to curb greenhouse gas emissions. Doing so is easier said than done since it requires major infrastructure change, money, and political will. However, farmers in Dorchester County have options that address the effects they are already experiencing. Broadly, farmers can decide between cutting their losses and abandoning patches or entire fields, changing land use to adapt to sea level rise, and building infrastructure to resist rising tides. Adaptation options include planting to attract wildlife and game, building solar farms on salty soils, or planting salt-tolerant crops. Resistance sturctures can include berms, ditches, or tide gates.

Several  federal  and  state  financial incentives exist for farmers applying for easements. This policy compensates farmers for changing land use from agriculture to conservation. Additionally, due to sea level rise, the county's new structures must be raised two feet above a base flood level. On the coastline, the Maryland Department of Natural Resources has introduced a pilot program to build living shorelines to prevent erosion and protect shorelines from flooding. However, only one project of 24 proposed has been completed in Dorchester County. 

Eutrophication is the process that connects land management, water quality, and local economies in the Chesapeake Bay watershed. When there is an excess of nitrogen and phosphorus in the water, algae can bloom at harmful levels. “Dead zones” form when the algae die, sink to the bottom, and are decomposed by bacteria––a process that strips dissolved oxygen from the surrounding water. Dense algal blooms can also block sunlight from reaching underwater grasses that provide food and shelter for aquatic animals (Chesapeake Bay Foundation).

Agricultural runoff from farmland carries nutrients from fertilizers and animal manure into rivers and streams that flow into the Chesapeake Bay. Other sources of pollution include urban and suburban stormwater, wastewater, and airborne contaminants. Currently, the Chesapeake Bay's Total Maximum Daily Load (TMDL), a provision of the Clean Water Act, sets enforceable limits on the maximum amount of pollution the waterbody can accept to meet water quality standards for public health and healthy ecosystems.

Saltwater intrusion compounds nutrient management in the watershed by extracting nitrogen and phosphorus from agricultural soils after farmlands have been abandoned. Thus, regulatory efforts to control pollution must account for unanticipated nutrient loading from legacy nutrients in salt-damaged fields. To start, scientists and policymakers can identify the agricultural areas most at risk for nutrient runoff into the Chesapeake Bay as saltwater intrusion moves across the landscape.