We are supporting a large-scale research project to predict how shoreline development interacts with other stresses to change coastal ecosystems and the species that live in them. Research findings apply to the restoration of marshland and submerged aquatic vegetation as well as shoreline hardening. Coastal zone managers and land use planners can use the results to transform management from the current “parcel by parcel” approach to one that can consider the whole ecosystem.
Why We Care
Predictions of sea level rise have encouraged land-owners to install bulkheads and riprap (structure made of different kinds of rock or rubble) to protect houses and other structures. In some Chesapeake Bay tributaries, up to 80 percent of the shoreline has been “hardened” in this way. Unfortunately, these installations impede natural processes such as the growth of wetland plants and submerged seagrasses. Many estuarine animals need these habitats for survival and reproduction. Without healthy wetlands and undersea grass beds, animals such as the blue crab, white perch, and many water birds could decline.
The impact of shoreline hardening is cumulative. One bulkhead or riprap may have only a small effect on the overall estuarine system. But multiple projects can exceed a “tipping point” that could be catastrophic.
Our goal is to identify the “tipping point.” Is there a minimum amount of natural shoreline needed to sustain estuarine habitats and species? What will happen if natural shorelines decline past the threshold? Can the system recover if natural habitats are restored? We will also be looking at whether or not invasive marsh plants threaten recovery of these systems and if there is a connection between estuarine water quality and the amount of hardened shoreline.
What We Are Doing
Working in partnership with management agencies, scientists will predict what these multiple stressors do to Mid-Atlantic coastal ecosystems. It will identify any “tipping points,” estimate losses of economically important species, and support more informed and proactive environmental management decisions, such as individual decisions about shoreline structure permitting or where to encourage restoration efforts.
A large team of scientists is being led by the Smithsonian Environmental Research Center. They are:
- Relating watershed land use (primarily agriculture, developed, or forested land) and other factors such as wave energy, sediment supply, and water oxygen levels to the presence and abundance of seagrass meadows.
- Sampling fish and shellfish such as blue crab, white perch, mummichog, top minnow and waterfowl in areas with different shoreline types (natural, riprap, bulkhead, or shallow beach) to determine any differences in population size or overall species health.
- Comparing tidal wetlands with and without the invasive marsh reed Phragmites.
- Conducting before-and-after studies of the conversion of natural shorelines to riprap and the restoration of hardened shorelines to natural ones.
Once relationships are determined between these multiple factors and the health of estuarine habitats and species, then predictions can be made about the impacts of future watershed and shoreline development.
In addition to the leadership of Dr. Thomas Jordan of the Smithsonian Environmental Research Center, the project team includes investigators from the University of Delaware, Virginia Institute of Marine Science, U.S. Geological Survey, University of Maryland, Pennsylvania State University, and the Maryland Department of Natural Resources. This project is part of the Regional Ecosystem Prediction Program (REPP).
Project scientists are working with the Maryland Department of Marine Resources, Maryland Department of the Environment, the Virginia Marine Resources Commission, and the Delaware Department of Natural Resources and Environmental Control throughout the course of the project to develop predictive models and other tools that these agencies can use to set shoreline policies and target protection and restoration efforts.
- Target areas appropriate for the restoration of submerged aquatic vegetation (e.g., eel grass)—very light dependent through the development of mathematical models that predict how wave energy and underwater light limitation can affect this vegetation, and relate its presence and abundance to land use and shoreline hardening
- Identify appropriate areas for marsh restoration and protection to limit further invasion by Phragmites.
- Predict future trends in coastal habitat suitable for blue crabs, white perch, mummichogs, and other species. These predictions can be integrated into fisheries production models, and help to manage coastal fisheries.