Inwood Hill Park Native Vegetation Restoration and Nature Center Refurbishment Project

Kirsten Stade

 
Abstract

Inwood Hill Park represents a relatively unspoiled natural environment on the tip of the major urban center of Manhattan Island, and contains some of the last remnants of the native forest and salt marsh ecosystem types that once spread over much of this island. Although Inwood is celebrated for its remaining forest and salt marsh, both of these ecosystems are much diminished from their former extent and productivity. This proposal seeks to restore the salt marsh ecosystem in the vicinity of the Inwood Nature Center to more closely resemble its condition prior to dredging of the lagoon in the 1940s, while restoring native vegetation to upland areas surrounding the Nature Center and refurbishing the Nature Center with elements of ecological design. Upland lawns surrounding the Nature Center, now dominated by nonnative turfgrasses, will be planted with native wildflowers, grasses, and shrubs. Banks of the lagoon will be graded and the edges of the lagoon filled with clean dredged sand to extend the area of suitable substrate for salt marsh plants, and a variety of plants including Spartina alterniflora, Typha latifolia, and Iva frutescens will be reintroduced or their existing populations supplemented. Finally, the Nature Center will be refurbished with composting toilets and a gray-water system for the purpose of reducing human impacts on restored vegetation and educating park visitors on the impacts of water use and waste production on the health of salt marshes and other native ecosystems.

 

 I.      Inwood Hill Park topographic, ecosystem, and biological diversity

 

Inwood Hill Park, located at the northern tip of Manhattan Island and embraced by the banks of the Hudson and Harlem Rivers, contains the last primeval wild forest and salt marsh ecosystems in Manhattan. Its dramatic topography is the legacy of the Wisconsin ice sheet that moved through the area 50,000 years ago, leaving steep hills, cliffs, valleys, and potholes in its wake and creating the varied terrain and diversity of habitats that now characterize the park.

 

As the only park on Manhattan Island that contains large tracts of native, unmodified forest, Inwood represents an area of vital refuge for many of the avian, lepidopteran, and small mammal species native to the area. The uniqueness of this forest habitat, combined with the potential productivity and ecological importance of the remnant salt marsh within Inwood, make this park a crucial stopover for many migrating and native wildlife species as well as an important place of refuge for human residents of the surrounding urban area. Although restoration efforts have been undertaken to curtail erosion, remove invasive plant species, and restore native vegetation throughout much of the wooded portion of Inwood Hill, no efforts have as yet been undertaken to restore functional, diverse habitat and natural conditions to the area surrounding the lagoon on the Harlem River Canal, which is the former site of extensive salt marsh wetlands. Now characterized by heavy human use and the location of the Inwood Hill Park Nature Center, this area would be an ideal site for restoration of salt marsh to a portion of its former extent and for the reestablishment of native plant diversity, both for its benefits to native wildlife and for its utility in educating the many park visitors about the importance of functioning ecosystems.

 

II.      Inwood Hill Park history

 

The names of features within and surrounding Inwood Park are evidence of its historical background. The central valley of the park contains the “Shorakapok Glen,” so named in honor of the native Lenape who inhabited the area prior to European arrival. The wooded slopes surrounding the glen still contain rock caves thought to have been used by Native Americans, and archaeological digs within the park have excavated several Native American burial sites. The shore overlooking the Spuyten Duyvil creek, which by 1930 was widened and dredged to form the Harlem River Canal linking the Hudson and Harlem Rivers, was also the legendary site of the trade of Manhattan Island to Dutchman Peter Minuit for $24 in trinkets in 1626 (Kieran 1959, Renner 2003).

 

Upon the arrival of the first Dutch settlers in Northern Manhattan, members of the Dyckman family were quick to purchase much of the land that now comprises Inwood Park (New York City Department of Parks and Recreation, 2001b). The land, desirable because of its proximity to the New York and Hudson River Railroad and its perspective of the Hudson River, attracted many wealthy New Yorkers who built expansive summer estates on its rolling hills. The driveways that once led to these mansions still exist in the form of some of Inwood’s meandering pedestrian walkways, and cisterns, used by these estates because of the high water table characteristic of Inwood, can still be found within the park (Renner 2003).

 

Inwood Park officially opened in 1926, following acquisition by the City of the numerous small privately owned parcels that had made up the park since the 1800s (Renner 2003). The Inwood Hill Nature Center was dedicated in 1995. A former boathouse, the building now serves as an interpretive center providing informational materials on the park’s natural history and a facility for the park’s restoration and educational programs.

 

Like most coastal areas of Manhattan, Inwood was once home to extensive tidal salt marshes that covered roughly 15 acres to the south of Spuyten Duyvil Creek. In 1899, this creek was dredged to form the Harlem River Ship Canal, and by 1942 the salt marsh was also dredged to form what is now the lagoon south of the Inwood Hill Nature Center. In the 1930s, the park was extended into the Hudson River through filling of the riverfront and the banks of the lagoon were stabilized through the formation of a rocky shoreline (Loeb 1986).

 

Though now highly modified by human activity, the area surrounding the lagoon and Inwood’s remnant salt marsh fragments still represent enormous ecological potential. To the end of realizing some of this potential, this restoration project will focus on this small area within Inwood Park.

 

III.      The need for restoration of Inwood Hill Park

 

As noted above, extensive restoration efforts are ongoing at Inwood Park to control erosion on its hillsides, remove exotic plant species, and reintroduce native plants. As yet, however, little attention has been devoted to restoring the native character of the area surrounding the Nature Center, despite the extensive modification that has occurred in this area and the role of the Nature Center in providing information to the public about the area’s natural history.

 

The proposed restoration project will focus on restoring native flora and fauna to the area surrounding the Nature Center, including the upland lawns and pedestrian walkways on the peninsula containing the Nature Center, the eroding banks extending from this upland area into the lagoon, and the remnant salt marshes on the bank of the lagoon opposite to the Nature Center (Fig. 1.) Although it would not be feasible to recapture entirely native conditions in this area, as to do so would likely mean elimination of the Nature Center and the return of the land on which it now rests to marshland, tremendous potential does exist at this site to recapture some of the former ecological potential and native diversity of Inwood Park.

 

Fig. 1. Proposed Restoration Sites near the Inwood Hill Park Nature Center.

 

The need for this restoration project is apparent from the highly modified character of the landscape, and its consequent diminished capacity to support biological diversity. While the remnant salt marshes are made much of in references to Inwood Park, in reality these marshes consist of a narrow strip of salt marsh vegetation that offers little of the productivity and habitat-providing capacity of functioning salt marshes. This project would have as its primary goal the expansion and restoration of functionality of these salt marshes, as well as the transformation of the Nature Center and its surroundings into a demonstration site of native floral and faunal diversity.

 

As the project would entail extensive construction and disruption of a visible, heavily used section of the park, it would be completed in several stages in order to allow visitation of the area throughout the construction period. Through whatever means possible construction activities would also be used as an opportunity to educate the public about restoration; interpretive signage and tours by park staff would be employed throughout the construction period.

 

As the Inwood Park Nature Center already attracts many school groups and other groups interested in the area’s natural attractions, park managers should encounter little difficulty in soliciting the help of volunteers in the implementation of portions of this project. The budget included below reflects the conservative assumption that all portions of the project will be implemented through contract labor; it is highly feasible that the cost could be significantly reduced through the active solicitation of volunteers for semiskilled tasks such as planting native vegetation, using hand tools to grade marsh substrate, and spreading salt marsh plant seed. To further reduce costs, managers should partner with universities and facilities such as the Bronx Botanical Garden to acquire native plants for the restoration of upland areas surrounding the Nature Center at no or reduced cost, as well as seedlings of those salt marsh plant species that establish more successfully through planting rather than seeding.

 

IV.      The Inwood Hill Park Native Vegetation Restoration and Nature Center Refurbishment Project

 

Phase I: Nature Center native vegetation restoration

Like most frontcountry portions of urban parks, the land surrounding the Inwood Park Nature Center has been designed for heavy foot traffic and ease of human access. Upland portions are covered with nonnative turfgrasses, which confer some local ecological benefits (Beard and Green 1994) but are far inferior to native flora in supporting native biodiversity and providing a natural environment for the educational benefit of park visitors. As evidenced by the many bare patches of sandy substrate surrounding park benches and between trees in the vicinity of the Nature Center, (Fig. 2) these grasses are also not ideally suited for the soil that characterizes this area. The landscape design that employs extensive nonnative lawns is also intended to encourage human use, and hence areas that feature these grasses are often subject to extensive compaction of soils.

 

Two grassy lawns surrounded by park benches and paved walkways are in the immediate area to the northwest of the Nature Center. The first portion of this project would remove the nonnative turfgrasses that are established in the more westerly –and further removed from the Nature Center--of these areas, and replace them with native graminoids, forbs, ferns, and shrubs. The entire 0.17 acre area, referred to as Native Plant Area 1 (See Fig. 1), would be planted with native vegetation characteristic of this area prior to intensive human use. Many native flowering shrubs, grasses and sedges, wildflowers, and ferns are both attractive and easily maintained, and

 

Fig. 2. Extensive bare soil areas currently in Native Plant Area 1.

 

require less water than turfgrasses. Grasses such as Pennsylvania sedge (Carex pensylvanica), and Sideoats grama (Bouteloua curtipendula) make excellent ground covers and produce seeds attractive to many native songbirds, and so would be ideally suited for planting throughout much of Native Plant Area 1. Native wildflowers such as Heart-leaved aster (Aster cordifolius) and Blue-stemmed goldenrod (Solidago caesia) produce showy flowers attractive to butterflies, and so would be ideal for planting around park benches for the enjoyment of park visitors (NRG).

 

To ensure successful establishment of newly planted vegetation, and to add to the complexity and health of the restored system, effort should be made to break up the continuous lawn that now extends across the upland areas surrounding the Nature Center by planting diverse types of vegetation and grading soil to produce surface variations. According to Larkin et al. (2006), such variations lend resilience to an ecosystem by providing diverse microhabitats for seed establishment and increasing the complexity of a currently quite homogenous landscape. Phase I of this project will therefore include the transformation of the area now covered by lawn to a diverse community of native shrubs, grasses, and forbs, along with features such as rock gardens to further enhance visual appeal and topographic heterogeneity. Many native species such as Mountain phlox (Phlox subulata) are both drought tolerant and prefer relatively barren soils like those surrounding the Nature Center, and so would lend themselves ideally to the creation of visually appealing and resilient rock gardens interspersed across these upland lawns (NRG).

 

The irregular surfaces and varied vegetation of restored areas would render them less easily traversed by humans, and hence less subject to degradation by the high volume of foot traffic that impacts most parkland lawns. To preserve sufficient human access to accommodate the area’s high visitation levels and maintain its attractiveness to visitors, flagstone walkways would be installed leading to park benches and several stations along the shoreline. Current park benches would be retained, and their appeal enhanced with native flowering shrubs and wildflowers planted around them.

 

The second portion of Phase I would endeavor to perform similar restoration of the 0.07 acre lawn area closer to the Nature Center, designated as Native Plant Area 2 (See Fig. 1). Along the walkway to the Nature Center (Fig 3), native flowering shrub species that are attractive to lepidopteran and avian wildlife, such as Shadbush (Amelanchier canadensis) and Common hackberry (Celtis occidentalis) (NRG), would be planted. Less drought-tolerant herbaceous species such as Rose mallow (Hibiscus moscheutos) could also be considered for this area, as its proximity to the Nature Center would make for convenience of watering by an easily-installed gray water system.

 

 

Fig. 3. The vicinity of the Nature Center and a portion of Native Plant Area 2.

 

 

Phase II: North Lagoon salt marsh restoration

While restoration of the upland areas surrounding the Nature Center would have as its focus the re-creation of a native landscape for the enjoyment of human, lepidopteran, and avian park visitors, Phases II and III of the project would focus on restoring part of the native salt marsh that once extended to the south of the Nature Center’s current location for the sake of recapturing this ecosystem’s enormous productivity and ecosystem services. 

 

The more than 20-acre area now occupied by the Nature Center and its surrounding lawns, the lagoon, and the soccer field to its south was once comprised largely of salt marsh. This extensive ecosystem, nourished by the brackish waters of the Spuyten Duyvil Creek as it flowed from the Hudson River to the Harlem River, would have likely consisted of a diverse community of native salt marsh plants dominated by Spartina alterniflora, or salt marsh cordgrass. This species, the dominant member of most Northeastern salt marsh communities, performs vital ecosystem services as it anchors their sandy substrates and supports a vast food web that lives in and around its stalks. Much of Spartina alterniflora’s ecological utility derives from what it does once it dies: as its stalks senesce they remain in place, decompose, and form a foundation of organic matter that feeds a teeming community of decomposers and supports the entire pyramid of productivity for which salt marshes are renowned (Giblin et al. 1980).

 

Although restoring Inwood’s salt marsh to its former extent would be impracticable, the restoration of even a small portion of this ecosystem could have profound impacts for the biotic communities of Inwood. The replacement of the rocky shoreline surrounding the lagoon with a salt marsh community of some extent would support insects and invertebrates, provide spawning habitat for fish and amphibians, and attract a diversity of avian species. A salt marsh ecosystem that more closely resembled the original salt marsh of Inwood would be a powerful educational tool for the park’s visitors, who come to Inwood for its natural character and would appreciate the opportunity to learn about its heritage.

 

The northern bank of the lagoon would be the starting point for salt marsh restoration activities, which would be conducted throughout with the intention of both restoring the ecosystem and offering educational opportunities to park visitors. Just beyond the fence separating Native Plant Area 1 from the lagoon is a bank that is largely denuded of vegetation, its bare soil showing between exposed roots of sparse woody plants (Fig. 4). This bank offers an ideal demonstration site for salt marsh restoration, as its soil is sufficiently moist to support some of the high salt marsh species such as Juncus gerardi and Spartina patens (Warren 1993) as well as perennial species such as marsh elder (Iva frutescens) characteristic of the transition zone from marsh to upland ecosystems (Bertness 1994). This site’s proximity to the Nature Center as well as its location adjacent to a pedestrian walkway and several park benches would make it an ideal site for demonstration of the quality of functional salt marshes to park visitors.

 

Tidal marsh ecosystems are characterized by distinctive patterns of vegetation associated with small variations in elevation, with one or a small number of “low marsh” species occupying substrate that is subject to regular inundation and a greater diversity of “high marsh” species colonizing banks at greater elevations (Larkin et al. 2006). To provide a gradient suitable for growth of the full range of salt marsh species, and to extend the banks of the lagoon to allow for adaptation of vegetation to changing environmental conditions, 25-30 cubic yards of sand would be spread over the bank southwest of Native Plant Area 1. The eroding bank depicted in Fig. 4 and descending to the lagoon from the fence would be covered with dredged sand and graded to form a gradual slope, while an additional 10-15 cubic yards of sand would be used to raise the bottom of the lagoon to extend the area suitable for Spartina colonization.

 

Fig. 4. Bare, eroded soil on north bank of lagoon.

 

The bank would then be planted with native salt marsh species, in accordance with their tolerance for the salinity and inundation levels characteristic of each elevation. In areas of low elevation, subject to regular inundation due to the fluctuating tides of the Hudson River extending into the lagoon, Spartina alterniflora would be planted through seeding. Spartina has been found to do best when seeded at 40,000 seeds per acre (USDA NRCS 2006); the area proposed for restoration during Phase II is roughly .0074 acres and could be planted with 300-500 seeds. Largely because of its visual appeal but also to diversify the low marsh community and add to its appeal to wildlife, seeds of the native broadleaf cattail (Typha latifolia) (USDA NRCS 2006) would be dispersed at intervals throughout the marsh area subject to inundation. Higher elevation portions of the bank, that would likely be subject only to occasional inundation, would be planted with transitional species including Iva frutescens, Juncus gerardi, Spartina patens, and Ammophila breviligulata (Loeb 1986, Disraeli 1984).

 

Phase III: South Lagoon salt marsh restoration

The south bank of the lagoon, now modified by the placement of large boulders and separated from a pedestrian walkway by a wrought-iron fence, was once a salt marsh that likely extended well into the area now occupied by the walkway and adjacent soccer fields. Although restoration of the entire extent of this former salt marsh would likely meet with resistance from the many users of the soccer fields and surrounding trails and walkways, the restoration of a portion of this extent would be feasible and also desirable from multiple standpoints.

 

Currently, the major remnants of Inwood’s celebrated salt marshes occupy a narrow strip along this south bank. The Spartina alterniflora occupying these patches is constrained from expansion onto land to its south by the considerable elevation of this land, which as noted above was filled to create the soccer fields and pedestrian walkway in the 1930s and early 1940s (See Figs. 5). The rocky substrate along the south bank of the lagoon also prevents the natural fluctuation of the salt marsh in response to changing tidal conditions, while the depth of the lagoon and likelihood of near-constant inundation prohibits the establishment of Spartina to the north of existing patches.

 

While future plans to repave or maintain the walkway in its current location might be reconsidered in light of the relative benefits of maintaining a 22-foot-wide pedestrian walkway and 4.5 acres of soccer fields as opposed to pushing back these features to make room for a more extensive and productive marshland community, these decisions will be left to future managers. At present, it is more feasible to extend the existing marsh into the lagoon by depositing sand on the south bank, grading it to provide habitat for suitable species, and elevating the bottom surface of the lagoon to provide more suitable habitat for colonization by salt marsh species.

 

Figs. 5. Pedestrian walkway and rocky substrate limiting extent of salt marsh on south bank of lagoon.

 

Roughly 10,000 cubic yards of sand would be sufficient to cover the extent of the south bank to a depth required for Spartina to establish and begin the slow process of growth, death, decay, and sediment accretion that results in a healthy salt marsh habitat that may support a vast array of invertebrate and other aquatic species. Sand will be deposited along the entire southwestern to southeastern perimeter of the lagoon fronting the pedestrian walkway (see Fig. 1), so as to create a gradual slope transitioning to upland areas as well as to fill in the edge of the lagoon to extend current suitable habitat for salt marsh species.

 

As on the north bank, suitable species for planting would be selected from existing remnant salt marsh patches in the area, from the Greenbelt Native Plant Center, and from participating institutions and universities. Spartina has been found to propagate successfully through both seeding and transplantation, although transplants may be more successful in restored sites subject to substantial ecophysiological stressors (Woodhouse et al. 1974). It is likely that throughout the lagoon, however, conditions are sheltered enough that plants could be established by means of seeding, which is by far the most economical approach.

 

Considerations in successful salt marsh restoration

In order to succeed in capturing and maintaining desired ecological traits over the long term, a restoration project must take into account a number of considerations related to the restoration site and the species of focus. While the upland portions of this project, due to their proximity to the Nature Center and their design as a more managed system, may with ease be maintained over time by the continual addition of water, nutrients, or new plants and topsoil, ideally the salt marsh will be restored in such a way as to minimize the necessity of such inputs. The realization of this goal will require that restoration efforts during each of the project’s phases be undertaken with sensitivity to physical and ecological conditions prevailing at the restoration site, and genetic and population-level characteristics of restored plant species.

 

a.      Genetic diversity

To begin with, a sufficient level of genetic diversity among introduced plants is necessary to ensure flexibility of the population overall in responding to environmental changes and uncertainty (Falk et al. 2006). To ensure this level of diversity, seeds for this project will be chosen from a variety of sources such as the Greenbelt Native Plant Center, a nursery on Staten Island that supplies restoration projects in New York City parks. Other seeds and seedlings may be collected from plants in the vicinity and from remaining salt marshes in areas such as Jamaica Bay.

 

In addition, the location of Inwood Park along the Atlantic Flyway and its current status as an important stopping ground for many bird species increases the likelihood that genetic exchange will occur among restored salt marsh communities and other salt marshes of similar species composition along the migratory pathway. Owing to this fortuitous location, the restored population faces a greater potential for health, elasticity and ability to adapt to environmental change.

 

b.      Metapopulation issues

Given a diverse genetic makeup of the founder salt marsh community and the potential for genetic exchange among individuals, attention must also be paid to establishing populations of a minimum size necessary for viability. Patches of introduced marsh plants must contain a minimum population size in order to withstand stochastic events and stressors that may emerge in the abiotic environment. Hence the budget (see below) should allow for seeding in excess of the number of propagules that are hoped to become established, to allow for the possibility that some sites will not succeed due to less than ideal conditions. As some areas are likely to become sources for the spread of salt marsh, and others are likely to fail to establish at least initially, budgetary allocations for seeding should reflect a range within which an exact amount will be determined through adaptive management.

 

In addition to ensuring that restoration sites contain a sufficient number of individuals, attention must also be paid to establishing a minimum number of suitable patches to ensure metapopulation persistence. Selecting a number of restoration patches on both banks of the lagoon will ensure exchange of genetic material among patches, particularly if sites for reintroduction are spatially arranged to allow for self-propagation (Falk et al. 2006). As the lagoon is a relatively small, enclosed area that is visited by many bird species, it is likely that any sites selected could rapidly spread to adjacent sites or sites across the lagoon.

 

c.      Abiotic constraints

While the lagoon’s historic occupancy by a salt marsh community suggests that its sheltered, sunny location offers ideal light and energy conditions for the reestablishment of a salt marsh community, some aspects of the abiotic environment have changed since the time of the original salt marsh and a successful restoration project must take these aspects into account. Water quality tests should be conducted in the lagoon to determine whether nutrient availability or lack of availability may limit target species growth. Sewage outflows into the Hudson and Harlem Rivers may impact water quality in the lagoon, and may need to be addressed for a viable salt marsh community to become established. Although in healthy salt marshes Spartina productivity may be limited by the availability of nitrogen (Howes et al. 1986), high levels of nitrogen enrichment that might result from sewage outflows would likely cause mortality of this and other salt marsh species.

 

d.      Topographic heterogeneity

The likelihood of success of a salt marsh community in this site could be further enhanced by the creation of surface variations in the process of adding and grading dredged sand on the banks of the lagoon. This project will be informed by other successful marsh restoration projects that have incorporated habitat heterogeneity into their design, as there is evidence that such efforts may further buffer restored systems from uncertainty and raise their likelihood of success (Larkin et al. 2006). Effort will be made to incorporate topographic heterogeneity into the design of salt marsh substrate, through the construction of rivulets and other small variations that mimic those that would be found in natural marshlands.

 

e.      Climate change and ecosystem equilibrium

While the restoration of Inwood’s salt marsh offers clear benefits to the many human and nonhuman organisms that utilize Inwood Park, and it is likely that the salt marsh, once restored, would enjoy tremendous popularity among those who already enjoy Inwood’s many natural attractions, the nature of ecosystems is to change and there is no guarantee that the salt marsh would be the final resting state of the proposed restoration area. Indeed, it is unclear whether the historic salt marsh of Inwood represented a stable equilibrium or was a step along the successional pathway for this area. Especially in light of changing climate, managers concerned with restoration must be aware that target restoration states may not be equilibria (Suding and Gross 2006).

 

The benefit of this restoration project is that while restoring a state that existed in Inwood for decades or centuries in times past, it will also increase the flexibility of the system to respond to environmental change by increasing the permeability of the lagoon banks and extending the area available for salt marsh species to colonize. This renders the system more adaptable and resilient in the event that sea level change renders formerly occupied areas inhospitable. Particularly in times of rapid environmental change, systems that embody traits of flexibility and means of adapting to that change are far more likely to persist and continue to offer the diverse benefits of a functioning ecosystem.

 

f.        Invasive species

The specter of changing climate and rising sea levels raises the possibility that conditions at the restoration site will shift so as to favor a different suite of species than those supported by the current environment. As noted by Millar and Brubaker (2006), restoration efforts are increasingly informed by the perspective that climate change may alter expected outcomes at a site, and lessen the degree of control managers have over its species composition.

 

In the case of Inwood, a warming climate may favor the establishment of invasive salt marsh species. The main invasive salt marsh species in the northeastern United States, Phragmites australis, has a lower tolerance for salinity than the desired native Spartina (Wijte and Gallagher 1996) and hence its growth along the Inwood lagoon may currently be inhibited by the brackish waters flowing in from the Hudson River. Climate warming and associated glacial melting will reduce the salinity of estuarine ecosystems such as those associated with the Hudson, and may liberate Phragmites from any constraint imposed by current levels of salinity. Although no Phragmites now exists within the proposed restoration area, wind-dispersed propagules could easily invade from a small patch now present on a sandy beach at the junction of the Hudson River and the Harlem River Ship Canal. In order to maintain the highly productive restored Spartina salt marsh and prevent its conversion to a Phragmites-dominated system, which is far less hospitable to decomposers due to the diminished nutritive quality of its decomposing stalks (NYC Dept. of Parks and Recreation, 2001a), managers should be vigilant in their removal of Phragmites should it come to invade the restoration area.

 

Salt marsh restoration in Inwood Hill Park: Conclusion

Re-establishing a Spartina salt marsh along the banks of the Inwood Hill Park lagoon would confer the substantial benefits of salt marsh productivity and habitat on the Nature Center and its surrounding environment. The entire lagoon was once occupied by Spartina salt marsh and its sheltered, brackish waters provide ideal conditions for the reestablishment of this and other associated salt marsh species. The reconstruction of salt marshes in two or more patches increases the likelihood of health and persistence of the entire metapopulation, and expands the benefits of this important habitat type to the numerous bird, fish, amphibian, and invertebrate species that depend upon it. The location of the restoration site at Inwood Park places it in the midst of the Atlantic Flyway, raising its utility for migrating birds and butterflies as they make their way across a heavily urbanized landscape and raising the likelihood of genetic exchange between this site and other salt marsh sites likely to be visited by avian species. And finally, the restoration site surrounds an interpretive center whose visitors will derive educational benefit from the ability to witness first-hand the restoration of a fully functioning native ecosystem.

 

Phase IV: Nature Center refurbishment

To complete the transformation of the Nature Center into a demonstration site for ecological restoration and sustainable management of native landscapes, this proposal includes several steps to refurbish the Nature Center with an eye toward the realization of ecological goals. Although water use of the average American has actually declined over the past 40 years due largely to innovations in toilet design, which have produced toilets that use an average of 1.5 gallons per flush as opposed to 6 gallons per flush (Specter 2006), residents of industrialized nations could still do much to decrease their water consumption. The use of composting toilets, and the reuse of gray water for irrigation, would go a long way toward the realization of this goal.

 

This portion of the project will refurbish Nature Center bathrooms with composting toilets and a gray water system that will redirect water used in bathroom sinks to irrigate plantings surrounding the Nature Center. Although green builders within New York and elsewhere have taken even more ambitious steps to ensure sustainable design of human structures, these two components are directly related to the success of the salt marsh and native vegetation restoration projects at Inwood and so are especially suited to the project as a whole.

 

As the decline of salt marsh ecosystems in Jamaica Bay has shown, salt marsh plant species are highly sensitive to water levels and nutrient contamination, both of which are intimately related to the consumption of water and production of wastewater by human communities. Although the exact causes for the decline of salt marshes in Jamaica Bay is unknown, it is likely that water pollution from sewage treatment plant overflow and sea level rise as a result of climate change have combined to cause mortality of the Spartina communities that are the backbones of this ecosystem.

 

The North River Sewage Treatment Plant, located on the Hudson River between 137^th and 145^th streets, receives all sewage from the Inwood area along with the entire western half of Manhattan and Riverdale in the Bronx. Although not in the immediate vicinity of Inwood, in the event of a sewage overflow this plant would discharge an untreated mixture of urban runoff, rainwater, and raw sewage into the Hudson River estuary (Novikov and Bagtzoglou 2006). The addition of composting toilets to the Nature Center will provide an opportunity for educating visitors about this danger and its potential impact on Inwood’s salt marsh and other native ecosystems. Composting toilets have the added benefit of minimizing demand on the city water supply, as they eliminate the need for water to flush; this feature would be a useful addition to educational programs designed to educate visitors about the importance of water conservation for ecosystems and wildlife.

 

Composting toilets are an element of ecological design that has been little utilized in urban environments, largely due to the difficulty of finding appropriate sites for the use of composted organic matter. The Inwood Hill Nature Center is an ideal location for a trial of this technology because of the facility’s single-story design and ease of access to the outdoors. With the completion of Phase I of this restoration project, an abundance of native vegetation with varying need for fertilization will exist adjacent to the Nature Center, providing additional incentive for the production on-site of low-cost composted material.

 

As a final component of Nature Center refurbishment, a gray water system will be installed for the irrigation of plantings in Native Plant Area 2 surrounding the Nature Center. This system will route gray water from Nature Center restroom sinks to an irrigation system that waters those plantings that are closest to the Nature Center. This design will allow for the inclusion of less drought-tolerant plants within Native Plant Area 2, as described above, and like the composting toilets will minimize water use and wastewater production and educate visitors about sustainable water use.

 

While ambitious, a plan incorporating gray water systems and composting toilets as design components would be both feasible and cost-effective at the Inwood Hill Park Nature Center. It is hoped that such a plan, once implemented, would demonstrate the feasibility of gray water systems and composting toilets in urban communities and motivate their use in many other parks and urban facilities in the years to come.

 

Conclusion

The Inwood Hill Park Native Vegetation Restoration and Nature Center Refurbishment Project will restore ecological functionality to a heavily used landscape that has great ecological and educational potential. The project will recapture some of the natural character, wildness and ecological diversity for which Inwood Hill Park is celebrated, and supplement restoration efforts that have to date neglected that portion of the park that is the most visible and has the greatest potential to support rare and valuable habitat and ecosystem services. With a modest investment of capital and effort, this project has the potential to transform what is already an oasis for humans and wildlife alike into a vibrant and unique ecosystem that supports abundant wildlife while offering an unequalled educational opportunity for human visitors.

 

 

 

Preliminary Budget

 

Item	Phase I	Phase II	Phase III	Phase IV
Labor: Construction	1 backhoe operator @ $30/ hour for 40 hours= $1200	4 slurry pump operators and graders @ $30/ hour for 16 hours=$1920	4 slurry pump operators and graders @ $30 / hour for 80 hours=$9600	2 Construction workers/toilet installers @ $30/ hour for 80 hours=$4800
Labor: Landscaping/ Planting	four landscapers and gardeners @ $30/hour for 80 hours: $9600**	2 seeders @ $30/hour for 8 hours each=$480**	2 seeders @ $30/hour for 40 hours each=$2400**
Labor: Other				2 plumbers/ irrigation specialists @ $30/hour for 40 hours each= $2400
Flagstones	220 sq. ft. needed, 160 sq. ft./ton; cost is $185/ton. ~1.75 ton= $323.75
Topsoil for augmentation as needed	~ 0.25 acres= 10,890 square feet=403 yd3 @ $18.95/ yd3=$7,636.85
Ruggedized interpretive signs	1 sign @ $30	1 sign @ $30		Two signs @ $30/sign=$60
Native upland shrubs, ferns, grasses, and wildflowers	300 assorted plants @ avg $10/plant=$3,000**
Native wildflower seed	1 lb. @ $60/lb= $60**
Clean dredged sand		30 yd3 @ $3/ yd3 =$90	10,000 yd3 @ $3/ yd3 = $30,000
Salt marsh plant Seed: Spartina comes 197,000 seeds per pound.		~300 seeds required for .0074 acres; @ $90/lb, required seed will cost $0.15**	60,000 seeds required for 1.5 acres; cost $28.**
Salt marsh plant seedlings		15 assorted plants @ ~ $6/plant=$90**	50 assorted plants @ ~ $6/plant= $300**
Composting toilets				6 toilets @ $1500/ toilet= $9000
Mulch/sawdust for use in composting toilets				$50/ month in perpetuity
PVC and other materials  for construction of gray water and drip irrigation systems				$1100
Total	$21,849.75	$2,610.15	$42,328	$17,360 + $50/ month in perpetuity

Grand Total: Maximum** of $84,147.90 + $50/month in perpetuity

**Some of total costs expected to be offset by volunteer labor and the donation of marsh plants and seeds by universities, botanical gardens, and other participating institutions

 

Preliminary Timeline

Phase I: April-May 2007

1.      April 2007: Tilling of soil in Native Plant Restoration Area 1, augmentation with topsoil and compost as needed

2.      April 2007: Planting of native plants throughout Native Plant Restoration Area 1

3.      April 2007: Installation of one interpretive sign along west edge of the area.

4.      May 2007: Tilling of soil in Native Plant Restoration Area 1, augmentation with topsoil and compost as needed

5.      May 2007: Planting of native plants throughout Native Plant Restoration Area 1

6.      May 2007: Installation of two interpretive signs, one along walkway to Nature Center and one along fence overlooking lagoon.

 

Phase II: June 2007

1.      June 2007: Deposition of sand on short stretch of north bank of lagoon

2.      June 2007: Grading of substrate to appropriate marsh elevations

3.      June 2007: Installation of interpretive sign near park bench overlooking lagoon

4.      June 2007: Seeding of four or more native salt marsh species on newly created bank

 

Phase III: June-October 2007

1.      late June-July 2007: Deposition of sand along much of lagoon’s south bank

2.      July 2007: Grading of substrate to appropriate marsh elevations

3.      July-August 2007: Seeding of four or more native salt marsh species on newly created bank

 

Phase IV: September 2007

1.      September 2007: Installation of gray-water system in Nature Center to capture water from restrooms for use on native plants

2.      September 2007: Installation of irrigation system to direct gray water to drought-intolerant plants

3.      September 2007: Installation of composting toilets in men’s and women’s restrooms in Nature Center

4.      September 2007: Installation of interpretive sign explaining the benefits and use of composting toilets

References

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