Part of a series of articles titled Crystal Clear: A Call to Action.
Article • Crystal Clear: A Call to Action
Crystal Clear: Restoring the Salt Marsh at Assateague Island

NPS Photo
Background
An estimated 90 percent of salt marshes from Maine to Virginia contain similar systems of mosquito ditches. These ditches at Assateague Island appear as scars on the landscape today despite not having been maintained or cleared since 1939. The original intent of ditching was to lower marsh water-table levels and drain mosquito breeding areas. However, lowered water-table levels and drained marsh pools have degraded wetlands and reduced the ecosystem services they provide. Mosquito ditching can change native vegetation and impact wildlife habitat. Ditches also reduce the capacity of wetlands to store floodwaters and recycle nutrients, a critical ecosystem service that maintains water quality. Adding to these concerns of degraded ecosystem conditions is that 55 percent of the impacted salt marsh is within a proposed wilderness area. During a 2008 pilot project, the NPS determined the most effective and lowest impact method of naturally restoring marsh functions is to refill ditches and replant them with native plants. Preliminary results from the pilot project indicate that sheet flow has been restored to the project area, and that the speed and elevations of fluctuations in groundwater levels have been moderated.Status
The NPS has successfully restored over 400 acres of marsh at Assateague using the lowimpact technique pioneered by the NPS. Restoration work will continue into 2014 and perhaps through 2016 depending on funding. Volunteers, including students from local schools, are providing thousands of hours of labor to restoring the seashore and learning environmental restoration by working alongside NPS staff. Monitoring plans are in place to scientifically evaluate marsh conditions prior to and subsequent to ditch restoration, using protocols established by the NPS Northeast Coastal and Barrier Network Inventory and Monitoring Program. These efforts are part of a long-term program to monitor ecosystem condition at the seashore and enable NPS scientists to evaluate how restoration is affecting salt marsh function. The program includes monitoring water levels through established tidal stations; monthly monitoring of groundwater level and water quality; and annual surveys of vegetation (marsh and seagrass), nekton (estuarine fish), and animal use. Results will inform adaptive management of the project and enable managers to adjust and improve restoration techniques.Last updated: April 9, 2023