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Tidal Exchange: Summer 2005

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Summer 2005 Issue

Harbor Estuary News Contents

Green Roofs
Recreating Natural Processes in Cities
(Click Here)
Cynthia Rosensweig, Stuart Gaffin, and Christina Stanton

Idlewild Park
HEP Priority Restoration Site JB24
(Click Here)
Michael Feller

EstuaryLive 2005 (Click Here)

An Aquatic Research Facility in the Heart of Flatbush, Brooklyn
(Click Here)
Dr. Martin P. Schreibman

American Horseshoe Crabs (Limulus polyphemus) (Click Here)
Dr. Mark L. Botton

Green Roofs
Recreating Natural Processes in Cities
back to top
Cynthia Rosensweig, Stuart Gaffin, and Christina Stanton

Green roofs are drawing increased attention in the United States as an attractive biological technology that can reproduce natural processes by turning currently underutilized spaces into productive and inviting environments. Total rooftop area in most cities is extensive. For urban areas such as NYC and Los Angeles it is around 10-12 percent, so “greening” many rooftops could have a large beneficial effect in helping to solve multiple urban environmental concerns. In the long-term, green roofs may offer a low-cost solution for reducing stormwater impacts, increasing green space, and reducing the urban heat island effect, all of which will help to promote ecological health in our watersheds and estuaries.

What are Green Roofs?

A green roof system is a roofing assembly consisting of vegetation, a growing medium, a drainage layer, and a waterproof membrane placed in layers over a traditional rooftop. Green roofs are typically thin, containing only 4-6 inches of growing medium planted with hardy, drought-resistant plants to minimize weight, cost, and maintenance. A 4-inch green roof system, generally referred to as "extensive", may have a maximum weight of approximately twenty-five pounds per square foot when saturated with water. However, if the building support structure permits, “intensive” green roof systems, those with a growing medium more than 6 inches deep, can be installed and allow for a more diverse range of flowers, trees, shrubs or crops, becoming an attractive outdoor space and amenity for the building.

Green roof design varies depending upon geographic location, climate, function, and preference. Green roofs can cover large apartment buildings, industrial facilities, shopping centers, homes, or simple garden sheds. While there are concerns over weight, potential fire risks and maintenance costs, green roof systems abound in Europe and are designed to match the needs and function of a roof. For example, a common type of green roof plant is sedum, a desert-adapted stone crop that has a high plant-water holding capacity and thrives in a lightweight growing medium. Typically only needing care just after being planted, sedums can go for long periods without any water, can grow in shade or hot sun locations, and can withstand the harshest of weather conditions.

Helping the Urban Environment

Green roofs offer a means by which urban areas can restore the natural environmental processes that are often lost due to increasing development and sprawl. One such process that can be recreated through green roof technology is the management of stormwater and stormwater runoff by reintroducing natural absorption back into highly impervious built-up regions.

The green roof growing medium acts in the same manner as organic soil by binding moisture and providing nutrients, aeration, drainage, and water retention. These attributes allow green roofs to absorb and percolate rainwater, not only reducing the peak volume of runoff, but also delaying it in time, which is equally important (see Figure 1). If there are enough green roofs in a given area, this reduction and/or delay will lessen the frequency or size of a combined sewer overflow (CSO) event, thereby reducing the amount of untreated sewage and stormwater entering the local waterways.

Scientific studies have documented the ability of green roofs to support stormwater management. 4A pilot project initiated by the City of Portland, Oregon, found that a green roof with a 4-5 inch growing medium and a 72% plant cover of succulents could absorb around 70% of the annual rainfall that fell on it. During summer storms, the roof retained 100% of the rainfall; at other times of the year, peak runoff rates were significantly lower for the green roof than for a non-green roof.

Another natural process that can be enhanced by the creation of green roofs is the cooling effect provided by vegetation. Traditional black rooftops become extremely hot on summer days, with peak surface temperatures reaching 150°F or more. This is due to their dark color and lack of available water for evaporative cooling. Green roofs, like grass meadows in city parks, cool by evapo-transpiration, resulting in peak surface temperatures that can be more than 50° F lower under the same weather conditions. These lowered temperatures benefit both the building owner and the city. For the building owner, lowered roof temperatures can reduce air conditioning requirements and lower associated electricity costs. For the city, a green roof means one less black roof acting like an open oven, heating the hot air in summer and contributing to what is known as the urban heat island effect. Estimates of the temperature increase created by the urban heat island effect in NYC range between 3° and 7° F (2°– 4° C).

Impacts of the urban heat island include increased energy demand; higher emissions of carbon dioxide and other pollutants; and greater incidence of health problems related to heat stress and air pollution.

Costs and Benefits

As is the case for any new technology, the costs associated with green roofs must be weighed against the benefits. For an individual building owner, the additional cost of building a green roof is typically $10 per square foot, approximately double the cost of a traditional roof. However, by reducing temperatures and protecting against UV radiation, green roofs are expected to last approximately twice as long as traditional roofs, thus avoiding one roof replacement cost.

The application of green roof technology is also a public issue. The benefits of reducing stormwater runoff, the urban heat island effect and energy demand can be achieved only if green roofs are adopted on a sufficient scale in targeted areas with significant stormwater or CSO problems (e.g., Newtown Creek or the lower Passaic River). For this reason, locally-collected data and validated models are essential in demonstrating how green roofs will function to reduce pressure on the urban infrastructure. For example, it is important to understand how well green roofs reduce runoff during the dormant winter season as compared to the summer growing season.

Green Roof Research at Columbia University

Among the various green roof research endeavors across the United States, scientists at NASA’s Goddard Institute of Space Studies (GISS) and Columbia University’s Earth Institute (EI) are working to better understand the interactions of green roofs within the physical, biophysical, and social realms of the urban environment. Columbia’s first graduate level course on green roofs, offered in Spring 2005, focused on quantifying the costs and benefits to private building owners. The overall goal of the green roof initiative at EI is to establish a green roof research station in the neighboring community to work on quantifying and enhancing the public benefits associated with green roofs.

GISS and the EI are also partnering with NYC schools to develop green roof pilot projects tied to the schools’ science curricula. In addition to all of the potential environmental benefits, green roofs have excellent scientific education value. Teachers can use them to help students understand air quality and health issues, horticulture, biodiversity, climate and weather processes, global warming, building energy issues, urban water systems and the harbor estuary ecosystem.

Green roofs are an innovative and exciting form of urban landscaping that can reduce stormwater runoff, increase green space, and decrease the heat island effect. Using the best cost estimates available, it appears that this technology has the potential to add significant environmental benefits for urban areas when compared to other mitigation/restoration techniques. As materials and installation become less expensive, an even greater ratio of benefits to cost could be achievable. One day, having a green roof in the city may be as common as having a yard in the suburbs – and our concrete jungle may again become a green oasis.

Cynthia Rosenzweig, Senior Research Scientist & Head of the Climate Impacts Group, NASA Goddard Institute of Space Studies Stuart Gaffin, Associate Research Scientist, Center for Climate Systems Research, Columbia University

Christina Stanton, Program Coordinator, Center for Climate Systems Research, Columbia University

For more information about green roofs, visit www.ccsr.columbia.edu or www.greenroofs.com.

Idlewild Park
HEP Priority Restoration Site JB24
back to top
Michael Feller

I grew up near enough to Jamaica Bay that we could pull horseshoe crabs out of the corner sewer with bent coat hangers. Much of my youth found me circumnavigating the bay by bike via the Belt Parkway Bike Path and winding through the marsh islands aboard my uncle’s boat. When I wasn’t biking, fishing, or bird watching in or around it, I was often pouring over Jamaica Bay maps. Road maps from the 1960s and 1970s showed very few of the green spaces that indicate parkland. Marine Park (which formerly included Dead Horse Bay), the most prominent green block on the map, was usually labeled as “PARK (Undeveloped)” or sometimes “PARK (Proposed)”. Otherwise, most of the undeveloped bayside landscapes appeared as featureless white spaces with no identity. Gradually through the 1980s the maps greened. After the creation of Gateway National Recreation Area the interior of the bay was green. Later transfer of land from other city agencies to the NYC Department of Parks and Recreation (DPR) – in large part the fruit of NYC Audubon and the Trust for Public Land “Buffer the Bay” initiative – resulted in an emerald necklace encircling the beryline archipelago of marsh islands.

And so I find myself continually chagrinned to see Idlewild Park on some of the most up-to-date New York City road atlases as a big vacant void, an undistinguished white wedge tucked away immediately north and east of JFK Airport. And roads maps are not the only places where Idlewild Park appears as a non-entity. Despite 20-plus years of Jamaica Bay Task Force meetings; Buffer the Bay and Buffer the Bay Revisted reports; and the Jamaica Bay Ecosystem Restoration Project; and despite it’s abundant ecological assets, Idlewild Park remains off the major planning, management, and restoration maps related to Jamaica Bay projects.

The scant attention given to Idlewild Park is entirely out of proportion relative to its size and ecological function. First, the park is big – about 200 acres. Next, it contains almost 150 acres of salt marsh: pristine and plentiful enough for nesting sharp-tailed and seaside sparrows, clapper rail, oyster catcher, and willet. The park’s marshes and waterways are frequently used by foraging osprey nesting in North Woodmere Park; northern harrier nesting in or around JFK airport; and, also near the airport, perhaps the last short-eared owls known to nest in the city.

The salt marsh here is the confluence of the four most extensive fresh water streams tributary to Jamaica Bay: 1) Springfield Pond’s outlet stream in Springfield Park to the west; 2) Conselyea’s Pond’s outlet stream in Brookville Park to the north; and 3) Hook Creek and 4) Valley Stream to the east. Big cordgrass (Spartina cynosuroides), salt marsh bulrush (Scirpus robustus), and water hemp (Amaranthus cannibinum) – three salt marsh plants adapted to lower salinities – make their only Jamaica Bay showing here. The potential fish habitat represented by these freshwater tributaries is as yet unplumbed. We are hopeful that future studies will determine what if any role the streams play as breeding sites for anadramous fish like gizzard shad and catadramous fish like American eel.

But everything in Idlewild Park is not ideal and immaculate. Most of the park’s 50 or so upland acres were created by a sanitation landfill that operated between the 1950s and early 1970s. A plan was in place to entirely fill the wetlands to provide a corridor for the proposed Nassau Expressway. The filling of wetlands to create land, including the area under JFK Airport, and road building made it necessary to route tributaries and tidal creeks through culverts, constricting flow to and from Jamaica Bay. Since 1993, NYC’s DPR and Department of Environmental Protection (DEP) have been working together to restore wetlands in the park through projects required to maintain and enhance DEP stormwater infrastructure. Significant improvement to the local environment and the larger Jamaica Bay ecosystem has been provided by the following:

• Restoration of 13 acres of tidal wetland planted with 80,000 marsh grasses

• Restoration of uplands created on landfill by adding tens of thousands of cubic yards of soil planted with 500 trees, 2,500 shrubs, 150,000 grasses and wildflowers; and

• Creation of a 2 acre fresh water wetland planted with 22,000 marsh plants representing 17 species

Even before the restoration was completed, muskrats, Fowler’s toads, marsh hawks, tiger beetles, and more than fifteen species of dragonfly and damselfly were cavorting in the new wetland. Many of the plant species used in the restoration had been entirely extirpated or were largely absent from the Jamaica Bay area. With their return to Idlewild Park, this site is now an important nucleus for dissemination throughout the region of species such as serviceberry, butterflyweed, swamp milkweed, New York ironweed, American holly, turtlehead, and others.

In 2000, the Eastern Queens Alliance (EQA), a coalition of local neighborhood civic association leaders, formed the Idlewild Park Preservation Committee (IPPC). The New York State Department of Environmental Conservation (DEC) provided EQA with grant funds to begin implementation of its IPPC strategic master plan - in collaboration with DPR and DEP - for ecological restoration and environmental education in Idlewild Park. IPPC continues to effectively promote improved ecological conditions in the Park and adjoining natural areas - traditionally known in the collective as Head of Bay - and recognition that these resources are critical, integral components of the larger Jamaica Bay ecosystem. Continued restoration of these natural areas is essential if the overall health of the Bay is to improve. Or to put it more concisely - if we starve the head, the body withers.

Michael Feller is Chief Naturalist with the NYC Department of Parks and Recreation.

EstuaryLive 2005 back to top

Join us for a LIVE, VIRTUAL TOUR of the Harbor Estuary on Thursday, September 22 from 11:00 am to Noon

Teachers and Educators – Take your students on a field trip through five of our nation’s estuaries without ever leaving your classroom! The NY-NJ Harbor & Estuary Program is hosting a one-hour webcast during EstuaryLive on September 22 and 23. This live, online, interactive field trip will be broadcast from Liberty State Park’s Caven Point Beach in Jersey City, NJ.

EstuaryLive brings the estuary into your classroom and provides your students with a platform to take an active role in the learning experience - they can ask real time questions during the field trips - and many of these questions will be answered live during the program. Visit www.estuaries.gov to register for EstuaryLive or to learn more about this free program.

If you have questions about how to participate, call Laura Bartovics, HEP Outreach Coordinator, at 212-637-3787.

An Aquatic Research Facility in the Heart of Flatbush, Brooklyn
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Dr. Martin P. Schreibman

This is the first in a series of articles highlighting one of the many fine academic institutions that conduct research and educational activities in the Harbor Estuary region.

The Aquatic Research and Environmental Assessment Center (AREAC) on the campus of Brooklyn College, CUNY is dedicated to basic and applied studies of aquatic organisms and the environments they inhabit. It has brought regional and international acclaim to Brooklyn College and CUNY for its achievements in biological and medical research; environmental assessment and restoration; economic development and job training; educational program development and community outreach.

AREAC and its predecessor research laboratory have a 40+ year history of using aquatic organisms to study the structure and function of physiological phenomena. It has been an early participant in research that studies the effects on reproductive system structure and function in fishes of environmental chemical pollutants that function as endocrine system disruptors and act as hormone mimics. The ability of our water recirculating systems to mimic field conditions in the laboratory has been a hallmark of our research. Using these systems, AREAC conducts successful captive breeding of horseshoe crabs and other aquatic animals for restoration of depleted natural populations.

AREAC staff and student scientists have, in recent years, completed several vital studies in the NY-NJ Harbor Estuary including: investigations of the impact of power plants on the fisheries on the Hudson River; water quality analysis in the Gowanus Canal; and oyster growth in Jamaica Bay. A comprehensive, multidisciplinary study of the Jamaica Bay portion of Gateway National Recreation Area (GNRA) was completed in 2002, in conjunction with more than 20 scientists from a number of institutions. The purpose of this project was to provide base line data to the US Army Corps of Engineers and the New York State Department of Environmental Conservation in their planning for the restoration of 11 sites on the periphery of the bay. We are currently cooperating with GNRA in studies and restoration efforts to control the loss of valuable wet land that constitute the islands and margins of Jamaica Bay.

A major endeavor of AREAC is the demonstration that Urban Aquaculture (“fish farming in the city”) is a feasible and important activity for economic development in New York and in other parts of the world. We believe that the success of this endeavor is based in the use of recirculating aquaculture systems. This rapidly growing industry has the potential to produce a constant supply of safe, nutritional, aquacultured products to a major market with millions of consumers, as well as to provide jobs and job training. Currently, we provide Brooklyn College-grown tilapia to homeless shelters and to environmental, civic and governmental groups.

Using the living resources of the AREAC facilities and near-at-hand natural resources, we are providing quality programs in urban aquatic ecological and environmental studies for teacher training and student education. Starting this summer, AREAC and Cornell Cooperative Extension will offer professional development in aquaculture and aquaponics to 20 high school teachers. Throughout the year, AREAC’s doors are open to school, camp and organizational group tours of the facility – we are a community and visitor-friendly resource. In addition to the tours, visitors are brought up to date on environmental issues and stewardship, urban aquatic and estuarine ecosystems, aquaculture technology, and fisheries management.

Dr. Martin P. Schreibman is the Founding Director of AREAC. Individuals interested in visiting or learning more about AREAC’s programs may contact him at 718-951-5631.

American Horseshoe Crabs (Limulus polyphemus) back to top
Dr. Mark L. Botton

The horseshoe crab is one of the most distinctive animals in the NY-NJ Harbor Estuary and surrounding waters. Biologists classify them as chelicerates (a group that includes spiders and scorpions), rather than as true crabs. Ranging from Mexico’s Yucatan Peninsula to Maine, Limulus is most abundant between New York and Virginia. During the Spring and early Summer, horseshoe crabs migrate from the deeper waters of the estuary and nearby continental shelf and come ashore to lay their eggs on sandy estuarine beaches, which are protected from the ocean’s waves. It’s common to see swarms of mating crabs on our shores during the evening high tides around the full or new moons in May and June. Most any sandy beach within the estuary is likely to have some spawning activity when conditions are right, though the best locations to witness large numbers of horseshoe crabs are Sandy Hook Bay and portions of Jamaica Bay, including Plumb Beach and the Visitor Center at the Jamaica Bay Wildlife Refuge. Females lay golf ball-sized clusters of greenish eggs in the sand, which are fertilized by nearby males. Each cluster contains about 4,000 eggs and, in total, each female lays about 80,000 eggs every year.

All of this potential food does not go unnoticed, as horseshoe crab eggs are eagerly consumed by gulls, shorebirds, and shallow water fishes. Some of these shorebirds, including Ruddy Turnstones, Red Knots, and Sanderlings, are long-distance migrants that spend winters as far south as Argentina and breed in the Arctic. Horseshoe crabs grow very slowly, and take 9-10 years to reach maturity. They feed on a variety of bottom dwelling invertebrates, including small clams, worms, and crustaceans. A purified component of horseshoe crab blood, known as Limulus amoebocyte lysate, is critically important to the pharmaceutical and health care industries in a state-of-the-art test to detect bacterial contamination (fortunately, more than 90% of the crabs survive the process of blood donation). Horseshoe crabs are also commercially important as bait for the eel and whelk fisheries. The growth of the bait industry along the mid-Atlantic coast in the past 10 years has contributed to recent declines in horseshoe crab populations in many areas, which has led to a series of protective regulations at the State and Federal levels.

Dr. Mark Botton, Professor of Biology at Fordham University, has been studying horseshoe crabs for nearly 30 years. His publications include studies on horseshoe crab mating behavior, feeding ecology, and conservation.


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