Application of Remote Sensing Technologies for the Delineation and Assessment of Coastal Marshes and their Constituent Species

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• identify and delineate coastal marshes (CT and north shore of Long Island, NY) using
  moderate resolution satellite imagery;
• assess the marshes in the context of surrounding land cover, impervious surfaces and
  potential for future migration as a response to sea level rise;
• create a library of in situ spectral measurements for dominant marsh plant species
  throughout the growing season;
• distinguish among various types of dominant marsh vegetation using high spatial
  resolution commercial remote sensing imagery combined with in situ field studies at five
  select tidal marsh sites;
• determine the optimal spatial, spectral, and temporal resolutions of imagery for coastal
  wetland system characterization;
• provide the results of the research through web access and educational programs.

This research was supported by the United States Environmental Protection Agency Office of Long Island Sound Studies under the project “Application of Remote Sensing Technologies for the Delineation andAssessment of Coastal Marshes and their Constituent Species".

Coastal wetlands are a critical component of the Long Island Sound ecosystem. However, over the past century, a significant amount of these wetlands has been lost due to development, filling, and dredging, or damaged due to anthropogenic disturbance and modification. Global sea level rise is also likely to have a significant impact on the condition and health of coastal wetlands, particularly if the wetlands have no place to migrate due to dense coastal development. In addition to physical loss of marshes, the species composition of marsh communities is changing. Spartina alterniflora (salt cordgrass) and Spartina patens (salt marsh hay), once the dominant species of New England salt marshes, are being replaced by monocultures of Phragmites australis. During the past 30-50 years, P. australis is estimated to be spreading at a rate of 1-3 percent per year. It has been estimated that approximately 10 percent of Connecticut's tidal wetlands are dominated by P. australis and further evidence identifies approximately 50 percent of tidal and brackish wetlands in Connecticut as sites of P. australis invasion. P. australis outcompetes other marsh species in areas with increased fresh water, nitrogen and sediments and is positively correlated with marsh fragmentation. In response to the increase of P. australis in many marshes, The Nature Conservancy, the CT DEP and other organizations have instituted efforts (commencing in the 1980s) to restore marsh health, including the control of P. australis in some areas. The response of marshes to control activities has included both an increase of non-Phragmites marsh species and P. australis reinvasion. With the mounting pressures on coastal wetland areas, it is becoming increasingly important to identify and inventory the current extent and condition of coastal marshes located on the Long Island Sound estuary, identify techniques to track changes in the condition of wetlands over time, and monitor the effects of habitat restoration and management. 

Remote sensing was used to identify and delineate the extent of coastal marshes along the Connecticut and New York shores of Long Island Sound and distinguish among various types of dominant marsh vegetation within select marshes. This was accomplished through the use of Landsat Thematic Mapper and Enhanced Thematic Mapper moderate spatial resolution, public domain satellite imagery for the Sound-wide portion of the project with the more detailed assessment of the spatial extent of dominant marsh plant species using QuickBird, ADS40, and John Deere AgriServices high spatial resolution commercial remote sensing imagery combined with in situ field studies.

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