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Sudden
wetland dieback (SWD) is the rapid death of at least the
above-ground parts of saltmarsh vegetation or the failure of plants
to grow during a single or multiple growing seasons. Sometimes
it can result in the complete death of the vegetation.
Healthy saltmarsh |
Saltmarsh experiencing sudden wetland
dieback |
Aerial view of saltmarsh with 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 diebacks have 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.
While 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 high-value 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 production 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 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.
Please click here
to download a white paper on SWD ( 284
kb)
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