By Erin Dorset, Delaware Division of Fish and Wildlife
An expansive tidal wetland in the Inland Bays.
The Inland Bays are a beautiful and beloved part of Delaware, containing about 20% of the state’s wetlands. Those wetlands are important economically, culturally, and ecologically, as they improve water quality, support commercial and recreational fisheries, support tourism, absorb flood waters, and provide crucial feeding and nursery habitat for wildlife. However, the Inland Bays are also home to agriculture and booming development, and sea-level is projected to keep rising in the region, all potentially having negative effects on wetland acreage and health.
In light of all this, DNREC’s Wetland Monitoring and Assessment Program (WMAP) recently investigated the major problems that wetlands in the Inland Bays face and the best paths forward to ensure that wetlands in the bays are around for generations to come, creating an Inland Bays Wetland Restoration Strategy. To do so, WMAP gathered relevant existing data and reports, including their own tidal and non-tidal Inland Bays wetland condition reports, used expert input to list out the major issues and potential solutions, and used GIS mapping software to identify prime spots where wetland restoration could make improvements.
The Issues
Within the Inland Bays Wetland Restoration Strategy, WMAP identified the major issues that tidal and non-tidal wetlands face in the Inland Bays. They include:
Sea-level rise and land subsidence: The Mid-Atlantic region, including Delaware, is known as a hotspot for sea-level rise, meaning that waters are rising faster here compared with many coastal areas in the U.S. On top of that, land on the Delmarva peninsula is sinking, or subsiding, making the effects of sea-level rise even more pronounced. Sea-level rise and land subsidence can lead to tidal marsh edge erosion and drowning.
Marsh migration barriers: Tidal wetlands can shift inland naturally, or migrate, in many places as sea level rises, provided there are undeveloped lands with gentle slopes. With development increasing throughout the Inland Bays, opportunities for wetlands to migrate inland and save themselves from eroding and drowning are shrinking.
Invasive species: Both tidal and non-tidal wetlands suffer from the presence of invasive plant species, such as the European reed (Phragmites australis), Japanese honeysuckle (Lonicera japonica), and multiflora rose (Rosa multiflora). Invasive plants displace native ones, degrading wetland health and habitat quality.
Hydrology alterations: Ditching has heavily affected tidal and non-tidal wetlands in the Inland Bays. Ditches alter the natural movement of water through wetlands, which can reduce wetland health and negatively affect many plant and wildlife species that depend on natural conditions. Stream straightening or deepening (channelization) is also a problem in many non-tidal riverine wetlands, a practice which can increase stream bank erosion and disconnect floodplains from streams.
Habitat loss and fragmentation: It is estimated that about 60% of the wetlands that once existed in the Inland Bays have been converted and lost, and losses have been especially pronounced for non-tidal wetlands. Most losses are attributed to development, land clearing, and agriculture. Once wetlands are destroyed, so too are their beneficial functions, such as floodwater storage and water quality improvement. Wetlands that remain are becoming more isolated as losses continue, fragmenting important habitat and making it more difficult for wetland-dependent wildlife to survive.
An aerial view of extensive grid ditching in tidal wetlands in the Inland Bays.
A Path Forward
After reviewing the worst issues that wetlands are dealing with in the Inland Bays, WMAP outlined tactics in the restoration strategy that are likely to be the most effective at tackling those problems:
Promote nature-based solutions: Wetland restoration projects that aim to resemble natural conditions tend to be the most effective at restoring wetland health and function, and such projects would help combat wetland losses due to sea-level rise and erosion. For example, living shorelines can increase wetland resiliency against erosion and sea-level rise while absorbing wave energy and creating wildlife habitat. Another option is the beneficial use of dredge material, which can return sediment to drowning tidal marshes, giving them an elevation boost to help wetland plants, wildlife, and functions persist as sea-level rises.
Restore natural hydrology: Many potential actions could help address the widespread hydrology alterations in wetlands throughout the Inland Bays. Ditches in tidal and non-tidal wetlands could be filled in and stream channelization could be reversed, allowing for more natural water flow. Tax ditches could be improved ecologically by adding curves to channels, planting more trees along the sides, and minimizing mowing alongside them.
Improve land use planning: By thinking ahead, many wetland losses and impacts can be avoided. For example, by incorporating marsh migration and sea-level rise into future development and infrastructure planning, building can be prevented in key wetland migration pathways to ensure that wetlands persist, and property and infrastructure flooding challenges can be avoided. Natural buffers should be maintained adjacent to tidal and non-tidal wetlands when considering future development to maintain important wildlife corridors and reduce flooding risks near developments and infrastructure.
Preserve wetlands with easements or land acquisition: Land purchases and conservation easements are tactics that can preserve tidal and non-tidal wetlands for decades and help protect them from certain stressors. Lands that are highly suitable for marsh migration inland (e.g., undeveloped lands with gentle slopes) should be prioritized, as should natural areas that can connect fragmented forested wetland habitat patches. Funding should be secured to support such purchases, and landowners should be educated about their conservation options, such as the Conservation Reserve Enhancement Program (CREP), Working Lands for Wildlife Program, or Forestland Preservation Program.
Control invasive species: Controlling invasive species would improve wetland health and create space for more beneficial native species. The European reed (P. australis) should be treated in tidal wetlands as well as in marsh migration corridors. Landowners should be educated about DNREC’s Phragmites Control Cost-Share Program as well as how to identify other invasive plants and replace them with native species.
Minimize forestry impacts: To help address non-tidal wetland habitat loss and fragmentation, there are many ways to potentially improve forestry practices. Areas that have already been heavily timbered should have restored hydrology and be allowed to regrow to return to their natural state, and future clear-cutting in forested wetlands should be avoided. Best management practices (BMPs) that are already in place for forestry operations should continue, such as not harvesting in very wet soils and using tires that minimize soil rutting and compaction.
Beneficial use of dredge material to increase tidal marsh elevation.
Learn More
If you want to get into the weeds and know all the details, you can see the full Inland Bays Wetland Restoration Strategy, now publicly available! Spoiler alert: the full report contains information not only about tidal and non-tidal wetlands, but also about submerged aquatic vegetation (SAV) in the Inland Bays, including widespread problems faced by SAV and tactics to address those issues. You can also explore maps showing potential wetland and SAV restoration areas on public, protected lands in the full report, such as the one shown here. Restoration maps presented in the strategy combined spatial data from the Delaware Watershed Resources Registry (WRR) with other existing spatial data, including current wetlands, highly suitable marsh migration lands, areas containing P. australis, and poorly drained agricultural or rangelands.
Prime non-tidal wetland restoration opportunities in Little Assawoman Bay, circled in light blue.
The Wetland Monitoring and Assessment Program’s (WMAP) goal is to assess the health of wetlands and the functions and ecosystem benefits that they provide. We use this information to inform the citizens of Delaware and to improve upon existing education, restoration, protection, and land use planning efforts.
