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Tidal Wetlands Trends

Long Island Trends Analysis

The Long Island Tidal Wetlands Trends Analysis measures wetlands loss and changes in marsh condition within the Long Island Sound, Peconic, and South Shore estuaries including all or parts of Westchester, Bronx, Queens, Nassau, and Suffolk Counties. The results of this project are intended for use by environmental managers, conservation advocates and elected officials across a variety of regulatory agencies, environmental organizations, and governments.

Overall, Long Island's estuaries have lost approximately 2700 acres of native intertidal, high marsh, and coastal fresh marsh communities over the study period of 34 years (1974 and 2005/2008). This acreage accounted for between 10 and 100 percent loss of individual marshes.

Marsh loss was observed as:

  • The conversion of high marsh to intertidal marsh, and retreat of the seaward edge of the marsh,
  • The formation of pannes, ponds, and mudflats, as well as the widening of ditches within marshes, and
  • The intrusion of Phragmites australis

The complete report is available:

Jamaica Bay Trends Analysis

Over the last century, DEC has observed significant losses of vegetated tidal wetlands, principally Spartina alterniflora (intertidal marsh), in marsh islands of Jamaica Bay. Examination of historic maps reveals that between 1857 and 1924, the intertidal marsh islands area varied in size without trend, with average changes of up to 10 acres per year. During periods of significant storms, there were losses of marsh islands, but, during quiescent years, the marsh islands were able to rebuild.

From 1924 to 1974, 780 acres of marsh islands were lost due to direct dredging and filling (which were unregulated activities up to 1974) and 510 acres were lost (approximately 10 acres per year) due to other reasons. This information was obtained through analysis of aerial photography. A 2002 study (see first link in the right column) showed that the rate of loss of intertidal marsh islands accelerated from 1974-1999. Between 1974 and 1994, 526 acre of marsh islands were lost at an average rate of 26 acres per year. Between 1994 and 1999, 220 acres were lost at an average rate of 44 acres per year. The vegetated intertidal marsh is being converted to non-vegetated underwater lands. A photograph illustrating this conversion for Elders Point Marsh is shown below.

elder point marsh in 1999
elders point marsh in 1974

Photo On Elders Point Marsh in Jamaica Bay 76 acres of tidal wetlands were lost between 1974 and 1999.

Between 2003 and 2013, the net loss of marsh declined due, in large parte, to the restoration of nearly 150 acres of marsh island habitat. Still, despite these extensive restoration efforts, nearly 52 acres of tidal marsh still disappeared from the bay during this period. Contributing to the situation, the area suffered extensive flooding and surge damage during the landfall of Hurricane Sandy in October 2012, resulting in considerable shoreline erosion and damage t both fresh and tidal marshes.

Tidal Wetlands Loss Workshop

The proceedings for the 2014 Long Island Sound Tidal Wetlands Loss Workshop is now available online at the Long Island Sound Study (link leaves DEC's website).