Avian Havens in the Concrete Jungle
By Shannon Robinson
Key Words: Green roofs, bird habitat, migration pathways, urbanisation, urban green spaces.
Summary
New York City is located in a crucial area for bird migration along the Atlantic Flyway. Due to the intense urbanisation of this city, the area has become inhospitable for the other-than-human world. While green infrastructure has been incentivised as a climate mitigation technique, it has also proven beneficial to the health of both migratory and local bird populations within the city.
Green roofs are a form of infrastructure that involves planting greenery on the roof of a building, and the extent of the vegetation can vary from a monocrop of low-maintenance sedum to a diverse space resembling a traditional park or garden. While many are installed as recreational spaces, most of them are intended as a climate mitigation features as they are very effective in lowering city temperatures and reducing stormwater runoff. In addition to these impacts, green roofs inevitably also create habitat for arthropods and bird species by increasing stopover sites in urban areas and supporting forage plants like flowers and berries. New York has incentivised the installation of green infrastructure through several laws and regulations, though the construction of these areas is not always possible as it depends on the structural capacity of the buildings and the cost of the materials. Additionally, the design of a green roof can impact the overall functionality of these spaces as habitat. The composition of the soils and plants, as well as the location and maintenance of these spaces all have impacts on the effectiveness of these areas. |
Ecological Genealogy
New York City is located along the eastern shore of the United States at the mouth of the Hudson River, which flows into the Upper New York Bay. The city's strategic location has contributed to its historical and economic significance, as it serves as a major hub for international trade, culture, and tourism. The land on which the city resides is home to several Iroquoian and Algonquin speaking Indigenous groups, whose territories reach through the Hudson River Valley and around the areas of lakes Champlain and Oneida. Algonquian peoples, including the Mahican and the Lenape nations, as well as the Haudenosaunee Alliance, which includes the nations of Mohawk, Oneida, Onondaga, Cayuga, and Seneca have been living in the Adirondack region since time immemorial (Onion et al., 2022) Particularly, the Lenape people have their traditional territories on Manhattan Island, and within the bounds of New York City.
The Dutch were the first of the Europeans to settle in the area before the British seized control and renamed the area New York in the year 1664 (Onion et al., 2019). By 1810, the city's population had surpassed 200,000 and it became known as the largest city in the western hemisphere (Onion et al., 2019). While it may not hold this title today, it is still by far the most populated city in the U.S., housing over eight million residents within the 787 square kilometres of land area that make up its five boroughs (Tikkanen, 2024). Large scale urbanisation has many negative impacts on the surrounding natural world through processes such as deforestation, habitat destruction, and excess freshwater extraction (UCMP, 2022). As extreme climate events are worsening, it's clear why cities such as NYC are looking for ways to include more green infrastructure into their designs (JLL, 2023).
Green roofs, or living roofs, are not a new innovation, but only recently have they gained recognition for positive climate and health impacts in major metropolitan areas. The Gardens of Babylon, whether real or a myth, are the first example of what we would consider a living roof toady. Supposedly to have been built in 500 BC in what is now Iraq, they were mainly installed for aesthetic reasons (Richardson, 2023). In more recent times, green roofs are known beyond their aesthetic values, and many communities and cultures have been using sod or other greenery to insulate their buildings from the heat and cold of the climates (Richardson, 2023). In 1931, the first modern green roof was installed in the U.S. atop the Rockefeller Centre in NYC as a ‘pocket garden’, or as a place for New Yorkers to enjoy greenery without having to leave the city. While the gardens are no longer open to the public, they still stand as the oldest green roof on a commercial building in America (Lee, 2013). Latterly other buildings have been motivated to include more green infrastructure into their design, though mainly as climate mitigation rather than for aesthetic reasons, as most green roofing is not accessible to the public or intended for recreation. While water and climate management may be a substantial motivator, the addition of green roofing has many more positive effects, including air pollution mitigation, and habitat creation for the many migratory and local bird species, as well as arthropods and pollinating insects that spend time within the urban landscape.
New York is located along the Atlantic flyway– a pathway followed by millions of birds from thousands of different species every year during the fall and spring migrations (NYC Parks, 2019). While these migration corridors are not a fixed path, and the actual route and distance may vary from season to season, it is well documented that urbanisation and mass land use change within cities is disrupting the travel patterns of many species (D. R. Partridge & Clark, 2018 & Kurtz, 2022). Of the four separate flyways in North America, the Atlantic Flyway is the most densely populated, with one-third of America's population living along it (Kurtz, 2022). This rapid growth and urbanisation has caused widespread habitat conversion and worsened the connectivity of these pathways, making the migrations longer and more strenuous for many species of birds (Kurtz, 2022). When migratory birds stop to rest in urban landscapes, they often use the city's green spaces as a stopover site (D. R. Partridge & Clark, 2018). Recognizing the importance of urban green areas for both migratory and breeding bird populations, prioritising the expansion of green spaces enhances conservation efforts and biodiversity goals (D. R. Partridge & Clark, 2018).
The Dutch were the first of the Europeans to settle in the area before the British seized control and renamed the area New York in the year 1664 (Onion et al., 2019). By 1810, the city's population had surpassed 200,000 and it became known as the largest city in the western hemisphere (Onion et al., 2019). While it may not hold this title today, it is still by far the most populated city in the U.S., housing over eight million residents within the 787 square kilometres of land area that make up its five boroughs (Tikkanen, 2024). Large scale urbanisation has many negative impacts on the surrounding natural world through processes such as deforestation, habitat destruction, and excess freshwater extraction (UCMP, 2022). As extreme climate events are worsening, it's clear why cities such as NYC are looking for ways to include more green infrastructure into their designs (JLL, 2023).
Green roofs, or living roofs, are not a new innovation, but only recently have they gained recognition for positive climate and health impacts in major metropolitan areas. The Gardens of Babylon, whether real or a myth, are the first example of what we would consider a living roof toady. Supposedly to have been built in 500 BC in what is now Iraq, they were mainly installed for aesthetic reasons (Richardson, 2023). In more recent times, green roofs are known beyond their aesthetic values, and many communities and cultures have been using sod or other greenery to insulate their buildings from the heat and cold of the climates (Richardson, 2023). In 1931, the first modern green roof was installed in the U.S. atop the Rockefeller Centre in NYC as a ‘pocket garden’, or as a place for New Yorkers to enjoy greenery without having to leave the city. While the gardens are no longer open to the public, they still stand as the oldest green roof on a commercial building in America (Lee, 2013). Latterly other buildings have been motivated to include more green infrastructure into their design, though mainly as climate mitigation rather than for aesthetic reasons, as most green roofing is not accessible to the public or intended for recreation. While water and climate management may be a substantial motivator, the addition of green roofing has many more positive effects, including air pollution mitigation, and habitat creation for the many migratory and local bird species, as well as arthropods and pollinating insects that spend time within the urban landscape.
New York is located along the Atlantic flyway– a pathway followed by millions of birds from thousands of different species every year during the fall and spring migrations (NYC Parks, 2019). While these migration corridors are not a fixed path, and the actual route and distance may vary from season to season, it is well documented that urbanisation and mass land use change within cities is disrupting the travel patterns of many species (D. R. Partridge & Clark, 2018 & Kurtz, 2022). Of the four separate flyways in North America, the Atlantic Flyway is the most densely populated, with one-third of America's population living along it (Kurtz, 2022). This rapid growth and urbanisation has caused widespread habitat conversion and worsened the connectivity of these pathways, making the migrations longer and more strenuous for many species of birds (Kurtz, 2022). When migratory birds stop to rest in urban landscapes, they often use the city's green spaces as a stopover site (D. R. Partridge & Clark, 2018). Recognizing the importance of urban green areas for both migratory and breeding bird populations, prioritising the expansion of green spaces enhances conservation efforts and biodiversity goals (D. R. Partridge & Clark, 2018).
Present conditons
New York City comprises over one million buildings, making up twenty percent of the total land area (Treglia et al., 2022). Including roads, parking lots, and sidewalks, seventy-two percent of New York's land mass is impermeable surface (Miccio, 2018). Within this only 736 buildings have living roofs installed as of 2016, which makes up less than 0.1% of rooftops within the city (Treglia et al., 2017). These roofs are not equally spread across the city, with most of them being found in midtown or downtown Manhattan (Treglia et al., 2017). Even when concentrated to this limited area, New York's system of green roofing has seen a benefit to migratory and local bird habitat, for nesting, breeding, and foraging grounds (Coffman & Waite, 2011).
Green roofing makes particularly good foraging grounds for avian species. Not only can green roofs support the growth of forage plants like flowers and berries, but these environments are known for supporting vast populations of arthropods, which are another common food source for many bird species (D. R. Partridge & Clark, 2018). A study done of green roofs in Manhattan show that insect species from a wide variety of taxa are approximately three times more abundant on green roofs than on conventional roofs (D. R. Partridge & Clark, 2018). The same study monitored bird populations on green roofs in comparison to conventional roofs and found that not only were bird sightings more frequent on green roofs, but there was also a greater diversity of bird species identified on green roofs compared to conventional roofs. Fifteen species of ‘urban avoiders’, which are birds that are not typically seen in the urban environment, were identified on these living roofs, such as the cedar waxwing (Bombycilla cedrorum) and the ruby-throated hummingbird (Archilochus colubris). The increase in sightings of these ‘urban avoider’ species indicates a shift in the behaviour of these birds in relation to an increase in green roofs (D. R. Partridge & Clark, 2018). Text BoxThe majority of these green roofs are found on privately owned buildings, namely residential. However, one of the largest contributors of green roof space in New York is the Javits Centre, which houses over 28,000 square metres of green space on its rooftop (Misdary, 2023). Prior to green roof construction, the Javits Centre was known as one of the deadliest buildings for birds within the city, as collisions with its large walls of reflective glass killed between 4000 and 5000 birds annually (Misdary, 2023). After a 450-million-dollar renovation in 2014, which included the installation of the green roof as well as the replacement of the glass to non-reflective surfaces, the Javits Centre is now a great supporter of bird life. Over sixty-five different avian species have been spotted in this space for a variety of activities– American Kestrels (Falco sparverius) forage on the abundance of insect species, Eastern Phoebes (Sayornis phoebe) rest and refuel during their long migration south, and Herring Gulls (Larus smithsonianus) build nests to lay eggs and raise their young (Misdary, 2023). While the construction of all types of living roofs inevitably creates new habitats, there are more elements of green roof designs that could be implemented to increase their impact on wildlife welfare (Coffman & Waite, 2011). Factors such as the types of vegetation used, the overall design of the space, and other properties combine to influence species diversity within the site (Coffman & Waite, 2011). Recognizing and integrating wildlife-friendly elements in the planning and implementation of living roofs can further enhance their impact on bird populations. |
Future Conditions
With increasing climate events impacting the city’s residents, New York is incentivising the installation of green roofs to deal with a variety of potential problems (Lee, 2013 & NYC Audubon, 2022). In doing so, they are making the city a safer and more welcoming space for many species of birds that use the urban area as foraging, breeding, and nesting grounds, and benefiting the more-the-human world in ways that we will need future research to truly understand (Kaufman, 2023).
New York City, as of 2019, has several local laws which work to encourage the installation of more green infrastructure on rooftops. Local Laws 92 and 94 state that all new buildings, buildings undergoing significant expansion, and buildings having their roofing replaced need to include green roofing or solar panels within their project (Treglia et al., 2022). Additionally, the Green Roof Tax Abatement is a program within the New York State Legislature. The abatement program offers a 160-dollar tax abatement per square metre of green roofing, which becomes a monetary incentive for building owners to work towards installations on their properties (NYC Audubon, 2022). While less than 0.1% of buildings in New York had green roofing installed as of 2016, the implementation of these local laws and incentives would promote the addition of living roofs to new buildings, and retrofitted roofs wherever possible. It is likely that the number of green roofs within the city has increased since they were last surveyed in 2016. Even with all these incentives, there are still several factors that may hinder the installation of green roofs on previously built, and even new structures. First, the structural load capacity of the building needs to be taken into consideration before installation can occur (Heller & Psencik, 2014). The weight of the waterproofing material, soil and substrate, and the greenery all need to be supported by the roof of the building, which often requires major renovation- if it would be possible at all. Additionally, when considering green roofing as a water retention feature, the weight of the retained rainwater also needs to be noted. A structural analysis must be performed by a professional engineer or a registered architect to determine if a given roof would be capable of withstanding the added weight that would come with a green roof (NYC Buildings, 2022). The cost of the retrofitting, installation, and maintenance is also a factor contributing to this difficulty, and property owners do not always want to go through with a renovation due to the upfront cost. Despite the challenges, more and more green roofing is being installed throughout the city. It is predicted that the biodiversity of each site will grow and shift according to its location and design, just as the roof of the Javits Centre saw continued development in the years after its installation (NYC Audubon, 2022). While the renovation on the Javits Centre had biodiversity and bird habitat in mind, most green roof installations do not have this as a main objective. Using local soils as well as local plant species can help to increase the functionality of living roofs as local and migratory bird habitat by more closely mimicking the local natural ecosystems and creating spaces with ecosystem characteristics closer to that of the pre-urbanisation area (Coffman & Waite, 2011 & Partridge, 2023). Current green roof infrastructure provides suitable, if not ideal, habitat for birds (Coffman & Waite, 2011). The expansion of the scope of green infrastructure in New York City to include the welfare of local and migratory bird species is required to make the most of these numerous projects. Further research is required to understand the extent and possibilities of green roofing in New York City, and how the designs can further help wildlife to thrive in urban settings. |
References
Allegra Miccio. (2018, January 9). Impervious surfaces – Water Watch NYC. Water Watch NYC. https://waterwatchnyc.com/tag/impervious-surfaces/#:~:text=Impervious%20surfaces%20cover%20approximately%2072,which%208%25%20are%20parking%20lots
Coffman, R. R., & Waite, T. (2011, July 1). Vegetated roofs as reconciled habitats: Rapid assays beyond mere species counts. Urban habitats. https://www.urbanhabitats.org/v06n01/vegetatedroofs_full.html
Heller, R., & Psencik, C. (2014, August 6). Is your building conducive to the installation of a green roof? 2014-04-10 | Building Enclosure. https://www.buildingenclosureonline.com/articles/84599-is-your-building-conducive-to-the-installation-of-a-green-roof
Jones Lang LaSalle Incorporated [JLL]. (2023, December 4). How are cities responding to the growing risks of extreme weather? https://www.jll.ca/en/trends-and-insights/cities/how-are-cities-responding-to-the-growing-risks-of-extreme-weather
Kaufman, A. (2023, December 14). A beacon of hope for the birds (and humans) of New York. Fordham Newsroom. https://news.fordham.edu/fordham-magazine/a-beacon-of-hope-for-the-birds-and-humans-of-new-york/
Kurtz, Steve C., (2022) Co-habitation and Migration: Urban Design for Bird Migratory Pathways. All Theses. 3901. https://tigerprints.clemson.edu/all_theses/3901
Lee, H. M. (2013). History of Green Roofs & the Urban Heat Island Effect | Shaping the future of New York City. https://eportfolios.macaulay.cuny.edu/macbride13/research/history-of-green-roofs-the-urban-heat-island-effect/
Misdary, R. (2023, October 30). How an 8-acre green roof atop the Javits Center is boosting NYC’s biodiversity. Gothamist. https://gothamist.com/news/how-an-8-acre-green-roof-atop-the-javits-center-is-boosting-nyc-biodiversity
NYC Audubon. (2022). Green Roofs and Infrastructure. nycaudubon.com. https://nycaudubon.org/our-work/conservation/habitat-protection/green-roofs-and-infrastructure
NYC Buildings. (2022). Green roofs - buildings. https://www.nyc.gov/site/buildings/codes/green-roofs.page
NYC Parks. (2019). Spring and fall migration in New York City. https://www.nycgovparks.org/learn/wildlife-in-new-york-city/spring-and-fall-migration
Onion, A., Sullivan, M., Mullen, M., Zapata, C. (2022, December 13). New York - Native American tribes, Immigration & the Harlem Renaissance. HISTORY. https://www.history.com/topics/us-states/new-york#new-york-s-native-american-history
Onion, A., Sullivan, M., Mullen, M., Zapata, C. (2019, March 15). New York City. HISTORY. https://www.history.com/topics/us-states/new-york-city
Partridge, D. (2023, June 22). The Migratory Bird’s-Eye View of Green Roofs - Designing Rooftops for birds | Dustin Partridge. Living Architecture Monitor. https://livingarchitecturemonitor.com/articles/the-migratory-birds-eye-view-of-green-roofs-su23
Partridge, D. R., & Clark, J. A. (2018). Urban green roofs provide habitat for migrating and breeding birds and their arthropod prey. PLOS ONE, 13(8), e0202298. https://doi.org/10.1371/journal.pone.0202298
Richardson, J. (2023, December 12). History of green roofing. https://www.renewableenergyhub.co.uk/main/green-roof-information/history-of-green-roofing
Tikkanen, A. (2024, January 25). List of the largest U.S. cities by population | Estimate, Census, New York City, & Facts. Encyclopedia Britannica. https://www.britannica.com/topic/Whats-the-largest-US-city-by-population
Treglia, M., McPhearson, T., Sanderson, E. W., Yetman, G., & Maxwell, E. N. (2022). Examining the distribution of green roofs in New York City through a lens of social, ecological, and technological filters. Ecology and Society, 27(3). https://doi.org/10.5751/es-13303-270320
Treglia, M, Gaffin, S., Rosenzweig, C., Eichenbaum-Pikser, J., Khanbilvardi, R., Susca, T., Horton, R., Bader, D., Kushnir, Y., Little, C., & Blake, R. (2017). The Nature Conservancy - Green Roof Mapping results. In The Nature Conservancy - Green Roof Mapping Results. https://www.nature.org/content/dam/tnc/nature/en/documents/NYC_GreenRoofs_Summary.pdf
University of California Museum of Paleontology [UCMP]. (2022, March 8). Urbanization - Understanding Global Change. Understanding Global Change. https://ugc.berkeley.edu/background-content/urbanization/
Coffman, R. R., & Waite, T. (2011, July 1). Vegetated roofs as reconciled habitats: Rapid assays beyond mere species counts. Urban habitats. https://www.urbanhabitats.org/v06n01/vegetatedroofs_full.html
Heller, R., & Psencik, C. (2014, August 6). Is your building conducive to the installation of a green roof? 2014-04-10 | Building Enclosure. https://www.buildingenclosureonline.com/articles/84599-is-your-building-conducive-to-the-installation-of-a-green-roof
Jones Lang LaSalle Incorporated [JLL]. (2023, December 4). How are cities responding to the growing risks of extreme weather? https://www.jll.ca/en/trends-and-insights/cities/how-are-cities-responding-to-the-growing-risks-of-extreme-weather
Kaufman, A. (2023, December 14). A beacon of hope for the birds (and humans) of New York. Fordham Newsroom. https://news.fordham.edu/fordham-magazine/a-beacon-of-hope-for-the-birds-and-humans-of-new-york/
Kurtz, Steve C., (2022) Co-habitation and Migration: Urban Design for Bird Migratory Pathways. All Theses. 3901. https://tigerprints.clemson.edu/all_theses/3901
Lee, H. M. (2013). History of Green Roofs & the Urban Heat Island Effect | Shaping the future of New York City. https://eportfolios.macaulay.cuny.edu/macbride13/research/history-of-green-roofs-the-urban-heat-island-effect/
Misdary, R. (2023, October 30). How an 8-acre green roof atop the Javits Center is boosting NYC’s biodiversity. Gothamist. https://gothamist.com/news/how-an-8-acre-green-roof-atop-the-javits-center-is-boosting-nyc-biodiversity
NYC Audubon. (2022). Green Roofs and Infrastructure. nycaudubon.com. https://nycaudubon.org/our-work/conservation/habitat-protection/green-roofs-and-infrastructure
NYC Buildings. (2022). Green roofs - buildings. https://www.nyc.gov/site/buildings/codes/green-roofs.page
NYC Parks. (2019). Spring and fall migration in New York City. https://www.nycgovparks.org/learn/wildlife-in-new-york-city/spring-and-fall-migration
Onion, A., Sullivan, M., Mullen, M., Zapata, C. (2022, December 13). New York - Native American tribes, Immigration & the Harlem Renaissance. HISTORY. https://www.history.com/topics/us-states/new-york#new-york-s-native-american-history
Onion, A., Sullivan, M., Mullen, M., Zapata, C. (2019, March 15). New York City. HISTORY. https://www.history.com/topics/us-states/new-york-city
Partridge, D. (2023, June 22). The Migratory Bird’s-Eye View of Green Roofs - Designing Rooftops for birds | Dustin Partridge. Living Architecture Monitor. https://livingarchitecturemonitor.com/articles/the-migratory-birds-eye-view-of-green-roofs-su23
Partridge, D. R., & Clark, J. A. (2018). Urban green roofs provide habitat for migrating and breeding birds and their arthropod prey. PLOS ONE, 13(8), e0202298. https://doi.org/10.1371/journal.pone.0202298
Richardson, J. (2023, December 12). History of green roofing. https://www.renewableenergyhub.co.uk/main/green-roof-information/history-of-green-roofing
Tikkanen, A. (2024, January 25). List of the largest U.S. cities by population | Estimate, Census, New York City, & Facts. Encyclopedia Britannica. https://www.britannica.com/topic/Whats-the-largest-US-city-by-population
Treglia, M., McPhearson, T., Sanderson, E. W., Yetman, G., & Maxwell, E. N. (2022). Examining the distribution of green roofs in New York City through a lens of social, ecological, and technological filters. Ecology and Society, 27(3). https://doi.org/10.5751/es-13303-270320
Treglia, M, Gaffin, S., Rosenzweig, C., Eichenbaum-Pikser, J., Khanbilvardi, R., Susca, T., Horton, R., Bader, D., Kushnir, Y., Little, C., & Blake, R. (2017). The Nature Conservancy - Green Roof Mapping results. In The Nature Conservancy - Green Roof Mapping Results. https://www.nature.org/content/dam/tnc/nature/en/documents/NYC_GreenRoofs_Summary.pdf
University of California Museum of Paleontology [UCMP]. (2022, March 8). Urbanization - Understanding Global Change. Understanding Global Change. https://ugc.berkeley.edu/background-content/urbanization/