Westchester Marshland Conservancy Wetland Changes 2002

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.