||West Harlem Marshlands -
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West Harlem Marshlands
Rapid urbanization in
Tidal salt marshes are important ecosystems
that occur in
the intertidal zone along the shorelines of estuaries, bays and tidal
(Broome et al. 1988). Wetland
habitats were once thought to have
very little value ecologically or economically which led to the
conversion of these valuable estuarine systems to agricultural, urban,
commercial, and recreational uses. In
the last century alone, it is estimated that 75% of the historical
the NY/NJ Harbor Estuary have been lost to development projects (NY/NJ
Estuary Program 1996). The only
remaining salt marsh habitat in
The value of salt marshes has been
recognized and has slowed
the loss of wetlands. Increasing
attention has focused on restoring and maintaining healthy and
ecosystems in the NY/NJ Estuary (NY/NJ Harbor Estuary Program 1996). All too often in the past, decision-makers
have separated developmental goals and environmental goals. In
Tidal salt marshes provide ecosystem functions and services that are vital to a healthy and productive estuarine system. These areas consist primarily of grasses, sedges, rushes and other vegetation which are periodically flooded by tidal forces (Broome et al. 1988). Marshes convert energy from the sun into primary production (Broome et al. 1988) and are among the most prolific ecosystems in the world in this aspect (Montalto et al. 2006). As transitional zones between uplands and estuaries, marshes recycle nutrients, stabilize shorelines, filter pollutants, and provide important habitat for valuable fishery species and other wildlife (Broome et al. 1988, Montalto et al. 2006).
This proposal will attempt to restore a
Ecological history of West Harlem Waterfront, Riverside Park
During the last glacial period which ended
years before present, the area we now know as
Sanderson (2003) combined detailed
geographic models along
with historical records and maps and natural history surveys to
Figure 2. Reconstructed
map of the upper Westside showing rivers,
wetlands (patchy blue area). A tidal
salt marsh most likely occurred near the shoreline at
In the 1840s, the
In the early 1900s, the park expanded
Despite the expansion of the park to
The West Harlem Waterfront is situated in a
valley that ran down what is now known as
Figure 3. A close-up view of
As with most areas of
Urbanization has transformed the natural
landscape of the
area into one of concrete and asphalt. The
heavy vehicular traffic and proximity of the streets,
A plan to address the environmental issues
at the West
Harlem Waterfront is proposed here. Urbanization
has contributed to the increase in pollution, reduced open spaces,
access to the shoreline (NY/NJ Harbor Estuary Plan 1996), and increased
vulnerability of the
Sanderson’s (2003) reconstruction of the
Figure 4. View
West Harlem Waterfront in November 2006 from
Construction of tidal salt marsh
The construction of 0.3 ha of tidal salt
marsh habitat is
proposed to soften and stabilize the shoreline along
Figure 5. Area bordered by red indicates the general area for the proposed site of tidal salt marsh restoration/creation. Map courtesy of Google Earth, accessed December 2006.
Coastal marshes along shorelines of tidal
rivers occur in
the intertidal zone of moderate to low energy (Broome et
al. 1988). Landfill will
be used to create land for the salt marsh off the shoreline of West
Waterfront. One of the challenges to
constructing a salt marsh in this site is the tidal flow and ebb of the
Figure 6. West
Waterfront Schematic plans as of November 2006 (From: New York Economic
Development Corporation. 2004.
Broome et al. (1988) recommends that gentle slopes of 1 to 3% are preferred for tidal salt marsh restoration. Gentle slopes can dissipate wave energy over a comparatively wider area and also allows a greater area of marsh. However, slopes must be sufficient for appropriate surface drainage to prevent ponding and subsequent increases in salinity due to evaporation (Broome et al. 1988). Some areas of slope may exceed 3% in order to a mixture of high and low marsh areas.
It is essential that the appropriate hydrologic processes of the site be used as drivers of the tidal salt marsh restoration. The wetland hydroperiod, or flooding regime, is responsible for the evolution, structure and function of wetlands (Montalto and Steenhuis 2004). Other than slope, the hydraulic properties of the marsh substrate determines the rate at which pore water drains out of the marsh, which in turn, influences the oxidation state of the marsh substrate (Montalto et al. 2006). These drainage patterns of the substrate influence the chemical properties of the soil and pore water, microbial and vegetative communities supported, rates of erosion, and sediment exchange (Montalto et al. 2006). Hydrologic processes to aim for include an 11 to 9 hour daily inundation zone for the low marsh and a 7 to 4 hour inundation zone for the high marsh (NYS DEC 2000), with the water table always within 10 cm of the marsh surface for the low marsh (Montalto et al. 2006).
Tidal ranges are important to consider as well in determining the zonation of the marsh. While tidal range could not be measured at West Harlem Waterfront, a tidal range of 1.3 meters was reported at The Battery (NYS DEC 2000). In general, intertidal mudflats are unvegetated areas which are only exposed during low tide, low marsh is submerged at high tide but exposed at low tide, and high marsh is only periodically flooded by spring and flood tides (NYS DEC 2000). Each zone will differ in the amount and type of plant species present, which is largely determined by the tidal regime (NYS DEC 2000). In addition, the highly invasive wetland plant Phragmites can be limited in sites that are frequently flooded (Warren et al. 2002).
The presence and absence of channels can influence how water drains from areas where the topography is relatively flat or away from the edge of the river (NYS DEC 2000). Artificial channels can be dug if it is found that certain areas are ponding at an undesired level, however it is recommended that channels be allowed to form by natural processes unless increased salinity in the substrate from ponding and evaporation becomes prohibitive for biological communities.
Tidal salt marshes are typically divided into three zones: mudflats, low marsh, and high marsh. Mudflats do not hold any rooted vegetation, but are often dominated by micro- and macroalgae, which are important for bacterial communities (NYS DEC 2000). The inundation period for mudflats is too long for rooted plants to survive.
In the low marsh, Spartina alterniflora is the dominant angiosperm of regularly flooded salt marshes (NYS DEC 2000). This species will be intensively planted as plugs with a mixture of equal parts sand, top soil and peat moss included. Seeding is not recommended at this site since it is only effective in sites with low wave energies (Broome et al. 1988). The plugs can be grown in greenhouses using seeds from other natural marshes in the NY/NJ Harbor Estuary. This can insure that the plants will come from a genetic reservoir that is adapted to the environmental conditions of the region. Seeds of S. alterniflora should be harvested as closer as possible to maturity or just prior to shattering (Broome et al. 1988). It is recommended that S. alterniflora plugs be planted 0.5 meters apart. This planting density has resulted in successful standing vegetative cover in relatively high energy sites (Broome et al. 1986). Other species in the low marsh will be allowed to colonize naturally. These species include rockweed Fucus vesiculosus, green algae Enteromorpha spp., and sea lettuce Salicornia europaea. While Phragmites may become invasive in the high marsh, an appropriate flooding regime in the low marsh should inhibit colonization by Phragmites.
In the high marsh, a mixture of S. alterniflora and S. patens will be planted at 0.5 meters apart as above. Spikegrass Distichlis spicata will be planted in lower densities among S. alterniflora and S. patens in the high marsh. Other species, such as switchgrass Panicum virgatum, sea-lavender Limonium caroliniamum, saltmarsh plantain Plantago maritime, and seaside gerardia Agalinis maritime, will be allowed to colonize naturally as well. Constant monitoring of plants in the high marsh will be essential to prevent the invasion of Phragmites, which prefers relatively drier sites to colonize (NYS DEC 2000, Warren et al. 2002).
It is estimated that about 20,000 plugs of S. alterniflora will be needed for effective restoration of 0.3 ha of salt marsh. This estimate also includes additional plants to compensate for early mortality of the transplants. The sandy substrate of the marsh provides very few nutrients for the initial establishment of plants (Broome 1988). Therefore, slow-release fertilizers will be used in the low marsh to help the vegetation establish itself. Planting will occur in the late winter or early spring to allow for a full growing season before the onset of winter.
Macroinvertebrates such as snails Melampus, isopods Philoscia, and amphipods Orchestia tend to return within 5 years, which is relatively early in the restoration process (Warren et al. 2002). Other macroinvertebrates important to salt marshes are ribbed mussel Geukensia demissa and fiddler crabs Uca spp. These organisms generally feed on organic matter and invertebrates, but are themselves food for many birds and fish (NYS DEC 2000). Thus, it will be important to monitor the presence of macroinvertebrates since they will attract species from higher trophic levels such as fish and birds.
Many fish are dependent on salt marshes for at least part of their life cycle. Fish such as mummichog Fudulus heteroclitus, striped killifish F. majalis, and sheepshead minnow Cyprinodon variegates live in salt marshes for most of their lives (NYS DEC 2000). Other fish, such as Atlantic silversides, use salt marshes as breeding habitat; while winter flounder Pleuronectes americanus, tautog Tautoga onitis, sea bass Centropristes striata, alewife Alosa pseudoharengus, menhaden Brevoortia tyrannus, bluefish Pomatomus saltatrix, mullet Mugil cephalus, sand lance Ammodytes americanus, and striped bass Morone saxatilis all use salt marshes as nursery habitat (NYS DEC 2000). Typical fish species assemblages return relatively quickly after restoration, but the time it takes for the abundance of particular species to compare to reference systems may take over 10 years (Warren et al. 2002).
A Spartina-dominated tidal salt marsh has been demonstrated to attract more bird species and a higher number of state-listed species than Phragmites-dominated marsh (Benoit and Askins 1979). In the early stages of restoration, marsh generalists such as song sparrows Melospiza and red-winged blackbirds Agelaius phoeniceus may be expected to be relatively more abundant than marsh specialists. However, in 10 to 15 years after restoration of Spartina-dominated salt marsh, it can be expected that marsh specialists such as the salt marsh sharp-tailed sparrow Ammodramus caudacatus and seaside sparrow Ammodramus maritimus will increase their use of the salt marsh while the generalists will decline (Warren et al. 2002). Other birds that may return to the area as a result of salt marsh restoration are long-legged waders such as herons and egrets (family Ardeidae).
Benefits of tidal
salt marsh restoration at the
As the constructed salt marsh becomes a self-sustaining ecosystem dominated by dense stands of Spartina along the West Harlem Waterfront, the community will benefit from the flood protection against storm surges that the marsh will provide (NYS DEC 2000). The risk for flood damage in this community is high due to the vulnerability of the area and the dense human population. This is the same deadly combination of factors that led to the unprecedented natural disaster of Hurricane Katrina in 2005. The increased protection against storm surges by itself is enough justification for the creation of tidal salt marsh habitat along the West Harlem Waterfront.
Being among the most productive ecosystems in the world in terms of primary production (Montalto et al. 2006), tidal salt marshes support complex food webs. Their production promotes populations of finfish, shellfish, crustaceans, and birds (NYS DEC 2000).
Stormwater runoff from roads directly
pollution of the
The restoration of tidal salt marsh will provide critical habitat for invertebrates, fish, and birds (NYS DEC 2000). While the primary production of salt marshes can support food webs, the physical structure of the marsh becomes important nesting and nursery habitat for birds and fish, respectively (Warren et al. 2002). This will increase the biodiversity of the area and restore some trophic interactions that had disappeared centuries ago.
This proposal is meant to complement the
Harlem Waterfront project that already includes several uses for the
including a walkway, bicycle path, boat pier, future building site,
for passive recreation, recreational fishing, a woodland, and a kayak
(NYC EDC 2004). The salt marsh can
provide bird watching and nature enjoyment activities.
The proposed building can house an
environmental education center that can take advantage of the unique
opportunity that the creation of the salt marsh will provide. The environmental education center can
educate the community about restoration and urban ecology, connect
the cultural and natural history of the
The estimated timetable for the tidal salt marsh restoration project from start to finish is estimated to be 2 to 3 years, but continued monitoring and management of the site will be a long-term commitment. It is unclear how long it takes for a constructed slat marsh to approximate functions of a natural salt marsh, but recent studies have indicated that key functions in constructed and restored salt marshes may take 10 to 30 years to reach a level comparable to natural salt marshes (Morgan and Short 2002, Warren et al. 2002). Thus, even after the marsh is planted, continued monitoring and management is necessary to track the trajectory of the functional development of the marsh. The following is a general timetable for the tidal salt marsh restoration:
Collection of seeds and growing seeds in greenhouse in preparation for planting. Adding landfill along the West Harlem Waterfront shoreline to become the structural base of the salt marsh.
Planting Spartina spp. plugs in intertidal zone.
Replanting of bare areas (if necessary).
Beyond year 3
Monitoring of site and using adaptive management approach.
Product/service Quantity Price
Labor 2000 person-hrs @ $35/hr $70,000
Sand (landfill) 4500 yd3 @ $3/yd3 $13,500
Plants 20,000 plants @ $1/plant $20,000
Fertilizer 0.3 ha @ $2000/ha $600
Contractor 3 years $90,000
The widespread loss of wetlands in
Benoit, L. K. and
R. A. Askins. 1999. Impact of the spread of Phragmites
on the distribution of birds in
Broome, S. W., E. D. Seneca, and W. W. Woodhouse, Jr. 1986. Long-term growth and development of transplants of the salt marsh grass Spartina alterniflora. Estuaries 9: 63-74.
Broome, S. W., E. D. Seneca, and W. W. Woodhouse, Jr. 1988. Tidal salt marsh restoration. Aquatic Botany 32: 1-22.
Cromley, E. 1984.
Montalto, F. A. and T. S. Steenhuis. 2004. The link between hydrology and restoration of tidal marshes in the New York/New Jersey Estuary. Wetlands 24(2): 414-425.
Montalto, F. A.,
T. S. Steenhuis, and J.-Yves Parlange. 2006. The hydrology of Piermont
reference for tidal marsh restoration in the Hudson River Estuary,
Morgan, P. A. and F. T. Short. 2002. Using functional trajectories to track constructed salt marsh development in the Great Bay Estuary, Maine/New Hampshire, U.S.A. Restoration Ecology 10(3): 461-473.
Naeem, S. 2006.
Biodiversity and ecosystem functioning in restored ecosystems:
principles for a synthetic perspective. In Foundations
of Restoration Ecology, ed. D.A. Falk, M.A. Palmer, and J.B.
New York City Department of Parks and Recreation. 2006. Forever wild: Inwood Hill Shorakapok Preserve. Accessed November 2006 at: http://nycgovparks.org/sub_about/parks_divisions/nrg/forever_wild/site.php?FWID=38.
New York State Department of Environmental Conservation. 2000. Salt marsh restoration and monitoring guidelines. Available at: http://www.dec.state.ny.us/website/dfwmr/marine/saltmarsh.pdf. Accessed November 2006.
Emergency Management. 2006.
Roe, E. and M. van Eeton. 2001. Threshold-based resource management: a framework for comprehensive ecosystem management. Ecological Applications 27: 195-214.
Sanderson, E. 2003. The Mannahatta project. Wildlife Conservation Society. Available at http://www.wcs.org/sw-high_tech_tools/landscapeecology/mannahatta. Accessed November 2006.
United States Geological Survey. 2003. Quaternary geology of the New York City Region. Available at: http://3dparks.wr.usgs.gov/nyc/morraines/quaternary.htm. Accessed November 2006.
Warren, R. S., P.
E. Fell, R. Rozsa, A. H. Brawley, A. C. Orsted, E. T. Olson, V., Swamy,
A. Niering. 2002. Salt marsh restoration in
Weinstein, M. P. and D. J. Reed. 2005. Sustainable coastal development: The dual mandate and a recommendation for “Commerce Managed Areas”. Restoration Ecology 13(1): 174-182.
Figure 1. British
Headquarters Map 1782 of the upper Westside of Manhattan (courtesy of
Sanderson, Wildlife Conservation Society). Modern