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Sudden Wetland Dieback

Sudden wetland dieback (SWD) was documented in Delaware's Inland Bays in 2006, and is characterized by rapid death or failure of saltmarsh vegetation to grow within a single growing season or multiple growing seasons. Most of the marshes that were impacted in 2006 are showing signs of recovery and no new occurrences of SWD have been documented through the 2013 growing season. However, SWD has highlighted how important these wetlands are and the need to better understand and protect them to ensure that they will continue to provide services to the citizens of Delaware.

Sudden wetland dieback has mainly impacted saltmarsh cordgrass ( Spartina alterniflora) and appears as brown vegetation. As the cordgrass deteriorates, the mudflats that usually support the plants become exposed. Rapid death of marsh grasses is cause for concern because these plants hold sediments and organic materials together. Without living plant communities rapid erosion and marsh losses can occur. The cause of SWD is unknown, however, scientists predict that it is an interaction of several human induced stresses including sea level rise and climate change.

Tidal marshes are among our most productive ecosystems, providing a wide range of ecosystem services, including nursery habitat for fish, wildlife habitat, recreational activities, shoreline protection, and carbon sequestration.

 Healthy saltmarsh

Healthy saltmarsh

 

 
 
  

What is Sudden Wetland Dieback?

Saltmarshes usually support lush summer crops of plants, primarily saltmarsh cordgrass (Spartina alterniflora). When SWD occurs, a marsh appears brown or dead because little or no live green vegetation is present and the dead plants from the previous year remain, or the underlying surface is exposed.

Although sudden wetland dieback has been occurring along the east coast from Louisiana to Maine for the past decade, the immediate cause of SWD is still unknown. Delaware's first instances of SWD were reported during the early summer of 2006 along the shore of our Inland Bays, and may lead to increased loss of valuable tidal wetlands from increased erosion and submergence.

Although several patterns of SWD have been observed in different regions, only mid-marsh or interior marsh dieback have taken place in the Inland Bays to date.

SWD sites have been known to recover, but data on these recoveries is sparse. Some sites on Cape Cod, for instance, have died back, started to recover, and then died back again. In some locations full recovery has been spontaneous, in others combinations of seeding and direct planting have been successful.

Because the Inland Bays area has already lost large areas of saltmarsh as a result of human activity, the additional loss of portions of these valuable ecosystems to sudden wetland dieback is of great concern. The potential for economic, social, and environmental impacts related to the loss of ecosystem services as a result of SWD is a very real and present danger. Saltmarshes protect coastal development and agricultural lands from erosion and storm surges, provide critical habitat for wildlife, regulate bay and coastal ecology by filtering and storing nutrients and sediments, help regulate climate, and provide invaluable aesthetic appeal.

Saltmarshes are extremely sensitive to disturbances that may affect their capacity to naturally maintain their elevation, and SWD is a new challenge that can cause decreases in marsh surface elevation when grasses die and result in the loss of the air spaces provided by healthy root structures. Dieback events need to be identified, monitored, and carefully managed to prevent rapid loss of these critical resources.

White Paper on the Status of Sudden Wetland Dieback in Saltmarshes of the Delaware Inland Bays, Winter 2007

 
 
Saltmarsh experiencing SWD
Saltmarsh experiencing SWD

Aerial of SWD
Aerial of SWD

 For additional questions or photos contact:
Andy Howard - Andrew.Howard@state.de.us
DNREC Watershed Assessment Section
820 Silver Lake Blvd., Suite 220
Dover, DE 19904
302-739-9939

Delaware Wetlands Home

 

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