Full report - Conservation Gateway

Chapter 2 - Coastal EcosystemsCharacterizing Coastal Shoreline UnitsEach CSU was characterized with respect to size, habitatdiversity, and condition in order to identify patterns bysubregion and by CMECS type.SizeSize is an important CSU parameter because many othervariables are likely to correlate with it. Size of each CSUwas characterized by shoreline length and hectares ofintertidal habitat. In general, the lagoon and river typesare much larger than the embayment or fjord CSU types,with an average shoreline length of 2,791 and 1,798 kmrespectively versus 690 and 483. Similarly, the averageintertidal habitat area of lagoons is 10 times that of embayments.This is why subdivisions of many lagoons andrivers into tier 2 subunits were deemed helpful. However,there is a large range in size within all four classes. In particular,riverine CSUs range from 7,163 km for the easternChesapeake Bay CSU to only 237 km for the Saco River/Scarborough CSU in Maine. There is corresponding regionalvariation in size of CSUs. In general, the highly indentedGulf of Maine coast is characterized by fjords, onaverage the smallest of the four types, so the CSUs of theGulf of Maine are on average one fifth the size of those ofthe Mid-Atlantic.Habitat DiversityHabitat diversity of CSUs was characterized in severalways. First, the length of each CSU shoreline was calculatedby major habitat type, as per the ESI. The ESI classifiesthe coastline into 22 categories, which was consolidatedinto the following eight categories for simplification of interpretation:1) beach, 2) flat, 3) marsh, 4) swamp, 5) rockyshore/cliff/platform, 6) non-rocky bluff/steep/platform, 7)manmade, and 8) undefined.Second, the amount of six intertidal habitat classes wascalculated (in hectares) for each CSU. Intertidal habitattypes were mapped by extracting intertidal coded polygonsfrom the NWI (US DOI FWS 2008) in the UnitedStates and by extracting coastal ecosystem polygonsfrom the Northern Appalachian Ecoregional Planningcoastal target polygon dataset (Anderson et al. 2006a) inCanada. The polygons were placed into the following sixintertidal habitat categories 1) unconsolidated shore (sand,gravel, cobble), 2) unconsolidated shore (mud, organic,flat), 3) emergent marsh, 4) forested wetland, 5) rockyshore, and 6) scrub-shrub wetland.The quantification of emergent marsh or vegetated tidalwetlands in the analyses presented here is differentthan the quantification of “tidal wetlands” in the NorthAtlantic Coast Ecoregional Assessment (Anderson etal. 2006b). Unlike the 2006 coastal assessment, whichlumped unvegetated tidal wetlands and some submergedlands into tidal wetland complexes, this assessment separatedout vegetated tidal wetlands (e.g., salt marsh, tidalmarsh or emergent marsh) from unvegetated wetlands.The rationale for this difference in approach is the desireto distinguish “wetland loss” and “wetland conversion” asthreats to these estuarine systems. With the exception ofvegetated tidal wetlands that get filled and or armored,“wetland loss” attributable to other causes is often firstevidenced by the loss of emergent vegetation and thensubmergence of land.Third, the amount of seagrass was calculated and thenumber of coastal salt ponds was counted within eachCSU. Unlike the NWI and ESI datasets, seagrass coveragewas determined by combining many different datasetsfrom federal, state and local data sources. These sourcesinclude Maine Department of Marine Resources, NewHampshire Department of Environmental Services,Massachusetts Department of Environmental Protection,Rhode Island Narragansett Bay Estuary Program,USFWS (for Connecticut), New York Sea Grant (for theHudson River), Peconic Estuary Program, (for PeconicBays, New York), NOAA Coastal Services (for LongIsland’s south shore estuaries), Rutgers Center for RemoteSensing and Spatial Analysis (for New Jersey), ESI (forDelaware), Virginia Institute of Marine Science (forChesapeake Bay and the Eastern Shore of Virginia), andTNC’s Carolinian Ecoregional Plan (for North Carolina).Data collection methods for seagrass coverage tend to varyby locality, as did year of data collection (1968 – 2008).For consistency at the regional scale, seagrass meadows2-22Northwest Atlantic Marine Ecoregional Assessment • Phase 1 Report