New England Marsh Dieback
(Nov 2008) Link to a website summarizing the state of knowledge about salt marsh dieback on Cape Cod. The link is: http://www.nps.gov/caco/naturescience/salt-marsh-dieback.htm
Ron Rozsa (Coastal
Ecologist with the Connecticut
Department of Environmental Protection - Coastal Management Program) contacted
the GCRC some years ago to alert us to some interesting observations concerning marsh dieback
in Connecticut and Massachusetts. What follows are a powerpoint "poster"
including some photos of dieback areas in Harwich (MA), a link to more of Ron's
photos, and notes from our correspondance with him.
Link to webpage "New England
Sudden Wetland Dieback" hosted by the New
England Estuarine Research Society.
"Are Cape Cod/Nantucket Sound marshes downing?"
[opens in new window]
Link to 2002
photos Herring River, MA
Link to 2004
photos Herring River, MA
Link to 2000
& 2004 photos near Branford, CT
each open in new window]
Ron wrote (JF
I just discovered your documentation of wetland losses in Georgia beginning
in 2002* - what a coincidence for the same (?) type of vegetation losses began
suddenly on the southern shore of Cape Cod, Mass. These losses continued
in 2003. *The Cape was well into a drought in
- the Cape is one large glacial sandplain - not bedrock. I assume that geology
is a contributing factor to where the wetland die-backs are occurring.
This dieoff was first notice by a colleague of mine, Scott Warren at Connecticut
College in the fall of 2002 when he took his wetlands ecology class to Cape
Cod for a field trip - Scott and I have been visiting these sites for years
- Scott longer than I. Some photographic evidence for 2000 sudden dieback
in CT has been found.
When he mentioned that - I remember seeing similar dieback on a nearby but
much larger system on the south shore of the Cape that summer. I then toured
several sites and took photographs - In general, most of the dieoff was in
the mid-estuary section of these tidal rivers/systems. We are beginning to
think that it is the mid-estuary that is most sensitive to changes in hydrology.
In 2003, I toured several more marshes - dieoff still present and present
in the new wetlands that I examined. I am attempting to have the EPA Narragansett
Bay lab fly the south shore of the Cape with their digital video camera so
that someone can record/map the extent of this problem.
In Connecticut, we have occurrence of low marsh vegetation losses in western
Long Island Sound that began pre- 1970's - and again most of the losses are
in the mid-estuary of our tidal rivers and coves - the same for New York state
Take a look at your losses and see if there is some common geographic pattern
- I would bet there is.
Would be interesting to know if this is occurring anywhere else along the
eastern seaboard on this time frame! A
colleague in New Hampshire claims this phenomenon is in their coastal wetlands
some correspondance he had with colleagues in Louisiana):
If memory serves
me the shallow SET (sediment elevation table) revealed no changes but the
deep SET revealed that the marsh was floating on the ground water and elevation
decreased with drought and restored when the groundwater recharged.
If in these cases, the rhizomes die - there is likely to soil collapse/subsidence
making the sites even wetter and less likely to support Spartina alterniflora.
What was different about the Cape Cod loss (compared to the Connecticut multidecadal
declines) was that is appears to affect both low marsh and high marsh (we
presently see no long term losses of high marsh vegetation in CT).