Suffolk County Vector Control and Wetlands Management Long-Term Plan Draft Generic Environmental Impact Statement May 3, 2006 5 Suffolk County Wetlands Background Information 5.1 Introduction CA determined that there are approximately 17,000 acres of vegetated tidal wetlands in Suffolk County, using a GIS interpretation of the National Wetlands Inventory (NWI) compiled by USFWS. Other accounts have found considerably more acreage (see Table 5-1), although the commonly quoted figure (which has no cited source) is 13,000 acres. Differences in the inventories listed in Table 5-1 stem from broadly sketched areas found in O’Connor and Terry (1972), and the inclusion of mudflats in the mapped definition of NYSDEC tidal wetlands. Map 5-1 (oversized, if print version; separate file, if electronic version) shows the agreed-upon names and locations of Suffolk County salt marshes, developed by CA, as agreed to by the participants of the Wetlands Subcommittee. This map will no doubt be improved on over time, as it is clear that local names and subdivisions of the marked salt marshes exist. Also, the map uses O’Connor and Terry as a base map, because that report named all of the areas it discussed (and so provided a basis for naming discrete salt marsh parcels); however, CA (and others) agree that maps such as the NWI (which does not name the salt marsh parcels) are more accurate in depicting the size and extent of salt marshes in the County. Table 5-1. Tidal Marshes in Suffolk County (acres) NYSDEC1 O’Connor and Terry2 NWI3 “Tiner Report”4 Peconic Estuary 21,658 20,241 4,492 4,188 South Shore 26,550 18,579 9,772 North Shore 6,399 2,575 Totals 45,219 16,839 1. As digitized in GIS format by NYSDEC (South Shore only) and NYSDOS (South Shore and Peconic Estuary only) 2. O’Conner and Terry (1972), as digitized in GIS format by Cashin Associates 3. Digital GIS format National Wetlands Inventory by USFWS, as interpreted by Cashin Associates 4. USFWS (1998) (Peconic Estuary only) Fresh water wetlands are important potential mosquito habitats, as well. NYSDEC mapping of regulated freshwater wetlands adds to 18,084 acres. Since NYSDEC regulates wetlands of 12.6 acres (two hectares) or greater plus nominated wetlands of local significance, the sum of freshwater wetlands in Suffolk County is likely to be considerably greater. However, it should be noted that Long Islanders have been diligent in nominating “wetlands of local significance” to NYSDEC, and so the difference is less than it might otherwise be. The NWI also includes fresh Cashin Associates, PC 487 Suffolk County Vector Control and Wetlands Management Long-Term Plan Draft Generic Environmental Impact Statement May 3, 2006 water wetlands, but CA has not attempted to interpret the NWI code system to determine GIS coverages of fresh water wetlands by NWI. Mosquito management options for fresh water wetlands are currently very limited under the current NYSDEC regulations. Fresh water wetlands tend to be more diverse than salt marshes, and yet the local systems have had less systematic study than salt marshes have. This makes the discussion of fresh water wetlands less focused than the salt marsh discussion. This background section therefore emphasizes salt marshes over fresh water settings, which may be more appropriate since more active management of salt marshes is envisioned under the Long-Term Plan. 5.2 Introduction to Suffolk County Salt Marshes The acreages listed in Table 5-1 are considerably less than was the case more than 100 years ago, and much less than the acreage of pre-Columbian wetlands. This is because wetlands have been filled for various reasons wherever people have settled (Mitsch and Gosselink, 2000). The environmental awakening of the 1970s led to laws and regulations limiting wetlands destruction, and New York State has a law specifying that there should be no net loss of wetlands (the Federal government has a similar Executive Order). There are disputes regarding the general trends for salt marshes, nationwide and on Long Island. Locally, two agencies of New York State (NYSDOS and NYSDEC) disagree over whether “most” Long Island marshes are losing area. Both agree that Jamaica Bay wetlands are suffering from a rapid and general decay. NYSDEC has found substantial rates of loss in the western portions of the South Shore Estuary system, and in select marshes in the Peconic Estuary as well as along Long Island Sound. NYSDOS has not found such problems. As part of the Literature Search for the project, a report on wetlands losses was prepared. The report found that generally, in Suffolk County, the loss of wetlands due to construction, dredging, and dredge spoil disposal has largely ended due to the Tidal Wetlands Act. There needs be a distinction between wetlands loss and wetlands conversion; wetlands loss implies the loss of natural habitat and wetlands conversion means the change from one habitat type to another. The conversion of vegetated wetlands to other habitat types is a natural process and has been occurring for years. There is concern that an increase in the rate of sea level rise will increase the rate at which vegetated wetlands are converted into other kinds of habitats, which may not have the same functionalities that wetlands do. The opportunities for the landward advance of wetlands in conjunction with Cashin Associates, PC 488 Suffolk County Vector Control and Wetlands Management Long-Term Plan Draft Generic Environmental Impact Statement May 3, 2006 sea level rise are limited due to anthropogenic alterations of the landscape. There are areas where the rate of wetlands conversion is particularly rapid and dramatic (for example, Jamaica Bay). Salt marsh islands appear to be most susceptible to rapid conversion. There are a number of possible causes for rapid conversion, which are discussed in detail in the report (Cashin Associates, 2006). There is general agreement that salt marshes and wetlands in general are threatened by factors associated with suburban development, including but not limited to: · physical encroachment onto the marshes, by near-vicinity development; · alterations of marsh hydrology, through coastline and bankside alterations; · changes in area hydrology, because of the creation of impermeable surfaces causing additional runoff and decreased recharge; · upland development, which causes changes to sedimentation patterns and chemical inputs to the marshes; and · offshore impacts, such as dredging or beach nourishment, which impact natural currents and sedimentation patterns. In addition, global forces such as sea level rise and general climate change can affect marshes (Mitsch and Gosselink, 2000). 5.3 Impacts of Mosquito Control Ditching on Salt Marshes Ditches were installed in nearly all of Long Island’s salt marshes, beginning in the 1920s (Cowan et al., 1986). This process was largely completed by public employment work crews in the 1930s (Glasgow, 1938), so that more than 95 percent of Suffolk County’s salt marshes have been ditched. Locations of the 32 salt marsh fragments that were not ditched are shown in Figure 5-1 (identified by reviewing USGS Quad maps, and confirming a lack of ditching using 2001 six- inch resolution aerial photography). Cashin Associates, PC 489 Suffolk County Vector Control and Wetlands Management Long-Term Plan Draft Generic Environmental Impact Statement May 3, 2006 Cashin Associates, PC 490 Suffolk County Vector Control and Wetlands Management Long-Term Plan Draft Generic Environmental Impact Statement May 3, 2006 Ditch construction and maintenance are sometimes characterized as traditional water management. Two kinds of constructed traditional water management were parallel ditching and grid ditching. Parallel ditching is characterized by the ditches running in one direction, generally, from the upland to the shoreline, with relatively constant distances between the individual excavations. The ditches are usually constructed so as to be perpendicular to the shore or major creek. This creates panels of vegetation separated by the waterways (Bertness, 1999). Grid ditching requires crosscutting the ditches, creating a grid of vegetation islands, and is sometimes called checkerboarding. Checkerboarding was used initially in larger marshes until it was found that parallel ditching was as effective as grid ditching, and required less maintenance (Richards, 1938). Ditches were installed with steep sides, typically up to three feet deep and two to eight feet wide (Dale and Hulsman, 1990). On Long Island, three to four feet was the most common width (Taylor, 1938). Distances between ditches were commonly 100 to 300 feet. Soil permeability was supposed to determine the selected width, with less permeable soils requiring closer ditching (Dale and Hulsman, 1990). Ditching was intended to reduce mosquito breeding by draining standing water on the marshes (Dreyer and Niering, 1995), and also by allowing fish access to breeding areas (Richards, 1938); ditching may also reduce oviposition sites by reducing the area of the marsh where damp soils can be found (Dale and Hulsman, 1990). The effectiveness of ditching as a mosquito reduction technique has been disputed (Nixon, 1982; Daiber, 1986), although most accounts agree that the combination of marsh filling and ditch construction in the early 20th Century did suppress mosquito populations sufficiently to allow for much greater development in many shoreline areas. This was particularly noted for the south shore of Long Island. Ditching was said to have resulted in the very ancient curse of Long Island [being] now well under control … the effectiveness of the ditches in controlling mosquitoes is so overwhelming … there seems to be no reason to oppose the ditching of all salt marshes. (Taylor, 1938). Cashin Associates, PC 491 Suffolk County Vector Control and Wetlands Management Long-Term Plan Draft Generic Environmental Impact Statement May 3, 2006 The overall impact of this ditching on the condition and health of salt marshes has been the subject of acrimonious disputes.