||Bayside/Acacia Cemetery -
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Listed By Ecosystem
Bayside Acacia Cemetery
Central Park's North End
East River Oyster Beds
Fresh Creek Marshland
Harlem River Yards
Inwood Marsh & Nature Center
Manhattan Marsh Re-creation
Manhattan Maritime Holly Forest
Northern Manhattan Forests
Operation Renovo Gardens
Time Capsule NYC
West Harlem Marshlands
An Experiment in Restoration
spaces and functioning ecosystems are precious and useful in an urban
setting. These habitats are often either
remnants of larger ecosystems that have been meticulously
preserved by humans or anthropogenically-created ecosystems that have
built from the soil up. The
Bayside/Acacia Cemetery, on the other hand, presents a diverse
habitat types that has, for the most part, assembled itself within an
environment. This site provides a rare
opportunity to study the process of succession and ecological theories
the theory of island biogeography) in an urban setting.
Given that the site has its own share of
ecological problems, including invasive species and pervasive edge
Bayside/Acacia also provides an arena for applying ecological
order increase biodiversity and ecosystem health. I
propose in this document a cost-effective
program of research and management that will both provide
much of restoration
ecology focuses on recreating ecosystems through the directed efforts
humans, wildlife can sometimes return to urban areas either without any
intervention or as a “side effect” of other human activities. The case of the High Line, in which an
abandoned elevated rail line running through heavily urbanized
Bayside/Acacia Cemetery is located in
The large-scale floral landscape of the site is clearly visible in aerial photos of the cemetery (see figure 1); the more detailed observations that follow result from personal visits I have made to the cemetery. A thickly forested band approximately 2.25 hectares in area extends south through the center of the cemetery from its north face. This forest is composed almost entirely of native oak, hickory, and sassafras trees. The canopy height ranges from about 10 to 15 meters. The trees are relatively young and the forest can be considered secondary growth, although it possesses some characteristics of a more mature forest (wider spacing between trees, possibly caused by placement of burial plots, and some downed wood). Very few understory shrubs grow below canopy level, and forest floor is almost completely covered by English ivy. This forest is bound by a “hard”, apparently maintained edge (where the landscape transitions very sharply between forest cover and much lower vegetation) on its east side and two softer edges (where the forest grades into shrubland and grassland) to the west and south.
Figure 1. Bayside/Acacia cemetery. Image courtesy <http://maps.google.com>
To the east of this forested area is a (rather infrequently) maintained area that stretches in band down the entire eastern edge of the site. Most of the floral cover in this area consists of grasses, wildflowers, and herbs, both non-native (e.g. Queen Anne’s Lace) and native (milkweed, Dutchman’s Breeches), with species mainly occurring in small patches and no one species dominating the area. Ornamental conifers and shrubs, as well as oak, hickory and sassafras saplings, also occasionally occur in this area. The areas to the immediate south and west of the forest, by contrast, contain large patches of taller shrubs interrupted by frequent clearings. The far western side of the site is actually fenced off from the rest of the site and is mostly a well-maintained, lawn-like area. In the northwest corner of the cemetery, however, the land slopes down into a shallow basin that is thickly covered with goldenrod (Solidago canadensis) interspersed with a number of small shrubs.
a large and fairly diverse community of birds. Most
of the birds that I observed in the site were small
passerine species accompanied by occasional gulls and other seabirds
strayed from nearby shoreline areas. Compared
to my observations of nearby
Scientific Theory and Research Opportunities
Bayside/Acacia provides a unique opportunity for urban ecologists to study how processes usually associated with “natural” areas, like succession, occur in a heavily developed environment and how well ecological theories, such as the theory of island biogeography, apply to urban ecosystems. The site’s diversity of habitats can be viewed as a function of succession, with different areas corresponding to different successional states. Those areas that have gone the longest without intensive maintenance (the forest, followed by the shrubby edge habitat that borders it to the west and south) most closely resemble climax communities. Succession is also actively proceeding within the site; oak, sassafras, and hickory saplings are beginning to grow around the edges of the forested center, and small shrubs are establishing themselves in the northwestern grassland area. Different areas of the site are also subject to different disturbance regimes (plots under “perpetual care” versus plots that are not regularly maintained). While succession can and often does occur when plots of land are left vacant in urban areas, development and land turnover usually occurs so quickly that succession is unable to proceed beyond the initial stages of grass and “weed” establishment.
Areas within Bayside/Acacia, however, have been remained undeveloped long enough to allow us to see how further stages occur. These factors make Bayside/Acacia a perfect site for studying the process of succession in an urban area. Comparisons can be made within the site (maintained vs. non-maintained plots) to determine how these regimes affect colonization by different plant species, and studies can be conducted using other sites that share similar climate conditions and current vegetation type but are not subject to forms of disturbance that this urban ecosystem experiences (pollution from automobile exhaust, for example) in order to determine what effects the urban environment itself has on the process of succession.
of island biogeography is often invoked in the context of urban
relatively few studies have empirically tested this theory in an urban
setting. A literature search conducted
by entering the terms “urban”, “island”, and “biogeography” into Google
yielded 3 relevant studies, one dealing with plants and the other two
birds. Crowe’s study of floral
colonization of vacant lots demonstrates many correspondences with the
of island biogeography; colonization of an area depends on factors such
distance to the nearest “island” of habitat in the urban milieu, the
other “islands” in the area, and the relative age of the “islands” from
colonists can originate (4). However,
this research was limited because of the issues of development and land
turnover mentioned before to examining only colonization by grasses,
and herbs. Bayside/Acacia provides an
opportunity to examine these issues in the context of a greater
plant species, including many larger trees and shrubs for which source
populations may be much rarer and dispersal events less frequent. The two studies of avian species, one
Invasibility, as well as many other characteristics relating to resistance to perturbation, is also affected the type of edge that delineates one habitat from another and the distance between this edge and the center. In forest environments, the increased invasibility and increased tree mortality and damage caused by proximity to the edge are most prominent in areas less than 100 meters from the forest edge (8, 9). As the forest is only around 100 meters wide at its largest, this means that this entire habitat is exposed to strong edge effects. However, the degree of contrast between the forest and its surroundings also influences the magnitude and the penetrance of these effects. A “sealing” edge, where the transition between the forest and its surroundings is extremely rapid, will experience strong effects at the boundary line; however, these effects will not penetrate as far into the forest as they would in a “softening” edge (8).
Bayside/Acacia faces problems associated with the manner in which it has been populated as well. While colonists from many common species may have had a number of source populations nearby from which to draw genetic diversity, some common species and most uncommon species may have only a few or even one source of colonists, creating a genetic bottleneck. It is important to identify both uncommon species growing on the site and common species that are underrepresented in nearby source populations as possibly genetically homogeneous.
The first priority in restoring Bayside/Acacia is the removal of the most troublesome of the site’s invaders, beginning with the English ivy infestation. Removal of an invasive species that dominates all other forest understory vegetation has been previously documented by Hartman and McCarthy, who treated an infestation of Amur honeysuckle (Lonicera mackii) using a “cut and paint” method. Plants are cut as close to the ground as possible, after which the exposed stem is “painted” with glyphosate herbicide (10). Instead of going to the extremes of either purely manual removal (which may actually encourage growth in English ivy (11)) or application of herbicide to the entire area, this method allows for targeted herbicide application that poses little harm to the trees occupying the forest. The National Park Service recommends a similar method for removing invasive ivy using a 25% solution of the glyphosate Accord and applying the treatment before the temperature drops below 50 degrees Fahrenheit (7). As Hartman and McCarthy found this treatment to yield a respectable but incomplete mortality rate of 94%, treatment should be continued for two growing seasons in order to ensure complete eradication. The authors found that this method consumed slightly over 1000 man-hours per hectare treated; given that most of the ivy occurs in the 2.5 ha forest, with isolated patches existing in the surroundings, a total of 3 ha would most likely need to be treated.
Cats can be managed both by exclusion (altering the existing fence to eliminate any openings large enough for cats) and by reducing prey availability through the installation of “squirrel boxes” or similar measures. “Cat-proof” fencing is commercially available and fairly cheap (12); a larger problem would be to limit access at the two points of entry into the site. Currently, two gates provide entrance to the park, one on the north side of the site and one on the south, and these gates are open eight hours per day. Installation of auto-latching chain-link gates at these two points would effectively prevent entry by smaller mammals while allowing larger mammals (i.e. humans) free access to the site. As hiring a full-time staff for the site is also part of the restoration plan, these employees could also be useful in tracking and removing any felines that managed to get into the cemetery. Finally, a small number of squirrel boxes, placed where trees are more sparse, may reduce the availability of small mammal prey to cats by reducing the likelihood that these animals would be caught out in the open (13). These features may end up attracting more squirrels to the site; however, as these animals would then be more vulnerable to predation by birds, this would ultimately reduce competition between cats and raptors.
In order to prevent the spread of edge-adapted plants into the forest center, I propose “hardening” some of the edges of the forest (i.e., to create a steeper gradient or a more abrupt shift between the forest and its surroundings) and increasing the total forested area. The more maintained western edge already has some of the desirable characteristics of a maintained edge, though it is lacking in dense understory vegetation. This could be remedied by planting native understory trees in this area following the removal of ivy. Hartman and McCarthy found that green ash (Fraxinus pensylvanicus) planted after the eradication of understory invasives grew better than five other native trees (10), possibly because it was better able to withstand the aftereffects of herbicide treatment or better able to grow in soil that had been depleted of nutrients by fast-growing invasives. Smaller native flowers and ferns could be planted at the edges as well to better prevent future invasions of the forest floor. For these, Dutchman’s Breeches (which is already found in some other areas of the site), Jack-in-the-Pulpit, and Christmas fern would be attractive choices. When replanting these species, care should be taken to obtain individuals from local populations (which may have local adaptations, specifically to urban areas) as well as individuals from a sampling of nearby areas in order to increase genetic diversity and future adaptive potential.
Increasing the actual area of the forest is a more ambitious project that may only be able to be completed on a longer time scale. It may be impossible to expand the forest in such a way as to create an area that is absolutely free from strong edge effects, as this would require at least 100 meters of forest on all sides of the “core area”. A combination of “hardening” the edge and expanding the forest, however, could create a forest core that is at least somewhat protected. This could be achieved by introducing something similar to the sort of “living fence” used in agriculture, planted so as to create a cantilevered edge that provides a shade and wind barrier (14), at the desired border of the new forested area. The “posts” for this living fence would ideally be fast-growing trees that provide plenty of shade and function well as windbreaks. The hybrid poplar (Populus deltoides x nigra), a commonly used landscaping tree that grows up to six feet per year, would be a god choice, although red maple provides a native option (15). Slower-growing oak, hickory, and sassafras saplings, as well as the understory plants mentioned previously, would then be planted several meters behind this fence, which would provide some protection from damaging edge effects while still giving these growing trees access to light. Again, saplings would come from both local populations (possibly even transplanting saplings that are currently growing in more maintained areas) and more distant regional populations in order to assure genetic diversity. The new forested area to be enclosed by this fence would be situated as close as possible to the site’s center to avoid the even stronger edge effects caused by the site’s urban matrix (see figure 2). The new forest to be created by this project would almost double the current forested area, raising it to 4 ha. This plan would leave areas at the north and south ends of the site unprotected by the living fence. Since some of the birds currently occupying the cemetery may use the “soft edge” habitats where more gradual ecotones exist, however, it would be best not to eliminate these edges altogether. Creating and maintaining more hard edges would allow for better control over the introduction of edge-adapted invasive species by focusing efforts to prevent unwanted introductions in the unfenced areas.
Figure 2. Position of the “living fence” and boundaries of the expanded forest
Image courtesy of <http:// maps.google.com>
While the creation of more forest would spur succession along toward a “climax” state, it would in doing so also reduce some of the diversity of habitats available to species living in the area. Thus, it may also be desirable to arrest succession in other parts of the site, maintaining shrubland or grassland communities in these areas. This is already done in maintained plots. Habitat diversity could be further maintained in additional plots located outside of the living fence (on the north and south ends of the forest. This could be conducted in an “experimental” manner (i.e. applying treatments to some plots and not to others) in order to study how the pace and other characteristics of succession. This would involve the establishment of 30 plots, each approximately 20 m on a side, near the southern edge of the site (see figure 3). Each plot would be assigned a random treatment (no interference, removal of saplings, or mowing). Plant species composition would be assessed once a month during the spring and summer for a period of five to ten years (in order to see the effects of succession on species composition of relatively fast-growing annuals as well as slower-growing perennials. Both presence/absence and abundance data would be recorded to determine richness and diversity in indices. This experimental approach can also be followed in the creation of living fences. Transects can be extended 100 m (i.e. the depth to which strong edge effects penetrate) into the forest in both fenced and non-fenced areas and indicators of edge effects, such as wind damage and invasive species prevalence, can be recorded on a monthly or quarterly basis.
Figure 3. Experimental design. Image courtesy <http://maps.google.com>
Most of these efforts are aimed at altering existing habitats or adding and removing species from the existing landscape. However, opportunities exist for fundamentally altering the present landscape and structure of the site as well. The existing site is flat and topographically homogeneous, with no bodies of water or hilly areas. Greater topographic heterogeneity is believed to cause greater niche diversity and thus greater species diversity (16), a phenomenon that as clearly noticeable in similar areas such as Green-Wood cemetery where the addition of aquatic habitats and human-made buildings and other microhabitats for nesting attract a greater variety of bird species. Bayside/Acacia still contains a fairly large area without gravesites, now mainly occupied by goldenrod, in its northwest corner that would be available for landscaping and alteration. As this area is still at a fairly early successional state, it would probably also be able to return to this state fairly quickly if habitat alterations disturbed the plant community here. This area is already located in a shallow basin and thus would naturally catch some water. The best way to use this area to vary the landscape and create additional habitat for birds and plants would be to create a pond in this corner (see figure 4). Land could excavated to form a 20 x 40 m pond, with the soil removed placed in a raised arc to on the northwest side of the pond site, which would prevent most urban runoff from entering the area. Even though the pond would catch its own water, water would probably also have to be added and circulated through mechanical means to prevent stagnation. To complement this habitat, another small pond could also be created within the cemetery, possibly in a small (10 m x 10 m) unused area that exists at the south end of the main forested band. It would be difficult, though not impossible, to create a watercourse running between the large pond and this small pond, possibly by employing existing footpaths as sites for a canal.
Figure 4. The proposed pond/hill habitats. Image courtesy of <http://maps.google.com>
Finally, the human use of the landscape would have to be taken into account. The caretakers of the site are obligated to maintain a certain number of plots at present, a task that already taxes the resources of the Shaare Zedek congregation. I would propose hiring four full-time employees to perform these duties as well as clean up trash, maintain existing trails, and carry out the research detailed above. The site already contains two buildings, one large manse by the northern entrance and one smaller, somewhat run-down building by the southern entrance, that can be used as interpretation centers. The larger building can be used as a repository of historical information on the site, while the small building can be renovated and function as an ecological education and information center.
While Bayside/Acacia is already a functioning ecosystem in many respects, restoration of the forest habitat would dramatically improve this functioning while returning the site to a more “natural”, historical version of the forests typically found in the area. The English ivy currently covering the forest floor, while very productive, is unable to perform some ecosystem functions and interferes with others. As a climbing vine, ivy does not rely on a deep root system beneath the soil, and therefore contributes little to soil retention and water filtration. Dense ivy cover also traps fallen leaves above the soil, preventing normal decomposition. A return to more diverse, native vegetation will probably reduce productivity but dramatically improve these other ecosystem functions and increase the system’s ability to resist perturbation through functional redundancy (18). “Hardening” the forest edge will also most likely prevent future harmful invasions and promote a healthier forest with less edge-dependent tree damage.
size of the forested area will also encourage bird diversity. Tilghman’s plot of
species richness against forest size indicates that an increase in
from 2.25 to 4 ha will increase diversity, on average, by almost 50%,
species-area relationship has yet to reach its asymptote (5). Natuhara and
study indicates that only some forest interior specialist birds
etc.) will not colonize smaller (<20 ha) fragments (6); however, it
interesting to see whether “hardened” edges create an environment
enough to the forest interior to attract these birds.
Creating an aquatic habitat and encouraging
greater topographical diversity will also attract bird species that
have previously used the site. A BACIPS
experiment involving comparisons between this site and the
of a bird- and plant-friendly environment in an otherwise inhospitable
area would have both ecological benefits for other green spaces in the
quality of life benefits for the people living nearby.
Bayside/Acacia is situated in a densely
settled band between
Finally, restoration would improve conditions for the human “inhabitants” of the site. The site’s current managers only maintain gravesites when necessary and are so financially constrained that basic maintenance (such as trash removal) is nonexistent throughout most of the site. Restoring the site as a natural area, while not its original use, would provide the impetus and labor to perform these basic functions as well as to maintain the “perpetual care” plots. Ecological restoration would also restore some dignity to those buried in the cemetery and their families.
alteration to the site, the addition of the two ponds and the
actually begin as soon as possible and will take several months. Invasive removal and the planting of the
“living fence” can begin in the spring of 2007. In
the spring of 2009 (when the ivy infestation should
eradicated and the poplar trees used for the fence should have reached
of twelve feet or more) re-vegetation of the forest (planting of
understory vegetation) can begin. While
the understory restoration will mainly be complete in the year
planting, the forest may take ten years or more to establish a canopy
comparable to that found in the existing forested area.
The research planned for the site will also
take place over a variety of time scales. Mowing/sapling
removal experiments can begin in the spring
Budget, Labor Required, and Funding
The maintenance of a full-time staff for the site will constitute a large, perennial expense. Hiring a staff of 4 to work for $20.00/ hour, 8 hours/ day, 200 days/ year (6400 person-hours per year) would cost $128,000 per year. Other costs would most likely be one-time expenditures on specific alterations to the site. Hartman and McCarthy estimate that understory invasive removal by the cut and paint method requires 1000 person-hours per hectare (10), meaning that removal from 3 ha would require 3000 person-hours. Although volunteers would be ideal, paying for removal (at $20.00/ hour) would cost $60,000. The concentrated glyphosate herbicide Accord costs $37.00 per gallon (19); given that a 25% solution is used for ivy, 10 gallons would most likely be more than enough ($370.00). Other invasive control efforts could probably be performed by the site’s staff. A commercially available cat-proof fence (12) costs $700/ 30 m, and cat-proofing the entire site (around 1200 m) would cost $28,000, with another $150 for two auto-latching gates (20). 500 m of living fence, planted with 1 hybrid poplar per 2 meters and costing $8.59/ young tree (15) would cost $2,147.50. Specimens of understory vegetation to be used for replanting can most likely be acquired from nearby parks and from the site itself. Replanting the 1.75 ha of forest with one specimen of northern red oak sapling ($10.46/sapling), one sassafras sapling ($17.96/sapling), and one shagbark hickory sapling ($17.96/ sapling) per 100 m2 (a reasonable estimate, considering each tree has a mature spread of approximately 10 m diameter and considering a fairy low rate of sapling survival) will cost $8,111.62 (15). Creation of the ponds will most likely be the most expensive aspect of the restoration. A kit for a 5m x 7m pond suitable for the smaller pond site costs $2000 (21), with the extra labor costs required for installation amounting to $20/ hour, 8 hours/ day, 5 days, 5 people, for a total cost of $4000. Constructing the landscape around the larger pond would hopefully not involve importation of fill, as earth excavated to create the pond could be used for this purpose. However, building a 20 m x 40 m pond (approximately 20 times greater in area than the smaller pond) would require materials costing at least 25 times as much as the smaller pond (given the more complex pump system required) and at least 30 times the labor (given the extra effort needed to create the surrounding landscape). So, a conservative effort for the cost of the construction of the large pond would be $50,000 for materials and $120,000 for labor (6000 person-hours), although costs could run much higher than this. Total one-time costs for the site improvements would cost $268,779.12 (table 1) and require 9000 person-hours of labor.
Table 1. Restoration budget
project seems fairly expensive, outside funding and assistance is
available. Community organizations and
local birding groups (such as the Queens Country Bird Club) provide
sources of volunteers and bird identification expertise (22). The best possible means of acquiring funding,
and the best possible fate for the site, would be “adoption” by the New
City Parks Department. The department
recently completed a similar program in