Hardening, or "armoring," of shorelines along the Chesapeake Bay is bad for waterbirds/USGS, Diann Prosser

In a finding likely to have widespread ramifications, U.S. Geological Survey researchers have concluded that structures built to protect Chesapeake Bay shorelines from storm surge and sea level rise are not good for waterbirds.

Humans like to live in many of the same habitats shorebirds like: coastal areas, overlooking rivers, with water a short stroll away. But as potent storms turn those placid, beautiful looking waterways into powerful, shore-beating waves, and as sea levels slowly creep higher, humans respond by "hardening" those shores with what USGS describes as "wooden, concrete or steel bulkhead walls or riprap borders that consist of piles of large stones or boulders."

Often, however, these structures are placed directly on habitat needed for shorebirds and waterbirds. Not only is habitat lost, but thesee structures can create changes in "food availability for many native coastal species, as well as contribute to the spread of invasive species," the USGS says.

The Captain John Smith Chesapeake National Historic Trail touches much, if not all, of the bay. Kayakers and canoeists who paddle its waters often are treated to displays of birds, whether it might be an eagle or osprey perched high in a tree surveying the water for a meal, great herons searching mudflats for a meal, or rafts of ducks.

The USGS researchers took many of these species into consideration in studying the issue of shoreline hardening. Waterbirds can be indicators of overall ecosystem health and when they are at the top of the food chain, as they are in the Chesapeake Bay, their declining numbers can cause cascading effects throughout the rest of the chain.

“This research will help managers make informed decisions to preserve critical species and ecosystem functions while also protecting against sea level rise,” said USGS biologist Diann Prosser, who is the lead researcher on this study.

Habitat Loss, Food Availability and Invasive Species

Shoreline hardening, or "armoring," can displace wetland habitat by removing natural vegetation, which is used by waterbirds for foraging, nesting and roosting, a USGS release explained. These conditions can reduce the diversity and abundance of prey, such as fish and benthic invertebrates. The altered environment also provides ideal conditions for the spread of a non-native species of Phragmites grass, leading to additional community degradation.

Waves tend to bounce off of armored shorelines, which can lead to changes in sediment composition as well as scouring and erosion of seaward habitats. The structures can also act as a barrier as shoreline habitats naturally migrate landward in response to sea level rise, leading to further habitat loss.

Riprap placed along shorelines of the Chesapeake Bay can adversely impact waterbird habitat/Integration and Application Network, University of Maryland Center for Environmental Science

Protecting the Bay

The Chesapeake Bay is the largest estuary in the United States. Its watershed includes more than 3,600 species of fish, wildlife and plants. The Bay produces an annual seafood harvest of about 500 million pounds, according to the Chesapeake Bay Foundation, making it third in the nation, behind only the Atlantic and Pacific Oceans.

The bay has thousands of miles of coastline and wetlands that are essential for staging during migration, wintering grounds and breeding habitat for waterbirds on the Atlantic coast. In recent decades, shoreline armoring has expanded in the Bay. Hundreds of miles of shorelines have been armored and it is expected to increase in the coming years in response to expanding urban development and regional sea level rise.

“The health of the Chesapeake Bay has been a concern for over 40 years,” said Prosser. “Our findings suggest that shoreline armoring is detrimental to waterbirds using the Bay and that continued expansion of armoring will be harmful to these communities. In addition, the study suggests that other human activities, such as agriculture and development, in coastal zones may have negative impacts on waterbirds.”

Informing Decisions and Exploring Living Shorelines

This work will aid coastal managers making environmental management decisions about land use and shoreline armoring to ultimately protect the Chesapeake Bay. This includes targeting of particular shorelines for protection and restoration efforts.

In addition, it will help determine whether living shorelines should be developed. Living shorelines are derived from organic materials, such as vegetation and oyster shells, to protect shorelines while preserving ecological functions. Preliminary research suggests that living shorelines may be able to counteract many of the negative impacts of traditional armoring on fish and invertebrates, but further research is needed to assess their ability to support waterbird communities.

The studies also might lead to similar studies elsewhere along the country's shorelines, such as at national seashores that attract shorebirds and waterfowl and humans in large numbers.