SUBMERGENCE OF NEW YORK'S SALT MARSHES A CASE STUDY IN WESTERN LONG ISLAND SOUND, NY
Marshlands Conservancy a wildlife sanctuary operated by Westchester County Dept. of Parks Study conducted with support from Friends of Marshlands Inc. Ellen Kracauer Hartig, Chris Pratt, Polly Endreny, Eymund Diegel (Mashlands Conservancy) Vivien Gornitz, (Columbia University and NASA/GISS)
Marshlands Conservancy
Submerged Wetland Sites, New York (source: F. Mushacke)
Mechanisms of Erosion - Coalescing tidal pools - fragmenting of marsh - die back of vegetation
Yellow Bar Hassock, Jamaica Bay, NY
Marshland Conservancy Location, Rye, New York (map source: Save The Sound) Residential Development
LOSS OF VEGETATED SALT MARSHES LONG ISLAND, NY Location
Adapted in part from F. Mushacke, NYSDEC
1974 Acres (Ha)
1994-2002 Acres (Ha)
Per Year
Lost
% Loss
NORTH SHORE – Long Island Sound Marshlands Cons. 25
(10)
15
(6)
- 1.5 %
Manhasset Bay
(10)
9.4
(4)
- 2.4 %
(121)
191
(77)
- 1.5 %
24
Stony Brook Harb. 300 SOUTH SHORE - Atlantic Jamaica Bay
1974
(799)
1223
(495)
- 1.5 %
Oyster Bay Area
1302
(526)
1018
(411)
- 0.9 %
30
(12)
18
(7)
- 1.9 %
437
(177)
450
(181)
- 0.14 %
Shinnecock BayIslands only Shinnecock BayShore only
Based on aerial photography comparisons between 1974 and (varies) 1994, 1995, 1998, 1999, 2001, 2002.
Old Canal New Canal
C
B
C D
C D
B
A
E
E
E
A
Marshlands Conservancy, Rye, NY
D
B
A
1926 wetlands still existing in 2002 1926 wetlands now submerged by water in 2002 1926 open water that is collecting sediment and in some cases, revegetating
Marshlands Conservancy, Rye N Changes from 1926 to 2002
Marshlands Conservancy, Rye NY
washed out wetland
Marshlands Conservancy, Rye NY
Marshlands Conservancy, Rye NY Overview of Site & Major Historical Issues
Marshlands Conservancy, Rye, NY Marshland Loss 1926-2002
+/- 5.4 acres lost
+/- 7.3 acres lost
+/- 5.3 acres lost
Upland 1926 marshlands still existing in 2002 1926 open water where fluctuating sedimentation gains have occurred 1926 marshlands submerged by open water in 2002
Total Marshlands in 1926:
+/- 42 acres
Total Marshlands in 2002:
+/- 24 acres
Total Marshlands lost over 75 years: +/- 18 acres
42% loss over 75 years
CONCLUSIONS
Aerial photos revealed accelerated marsh loss with recent losses of 3% per year. Land cover sampling showed 50% low marsh conversion to mudflats and original high marsh converted to low marsh. Some S. alterniflora gains found on sand.
Land use analysis revealed human alterations that may have contributed to marsh loss.
Ground observations indicate that mechanisms of marsh loss include: increased ponding, slumping along marsh edges, and widening of tidal inlets
Onsite salt marshes are unlikely to keep pace with accelerated rates of sealevel rise or urbanization impacts in the future.