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The Economic and Social Review, Vol. 45, No. 2, Summer, 2014, pp. 189–206
Sustainable Food Systems for Future Cities:
The Potential of Urban Agriculture*
KUBI ACKERMAN
The Earth Institute, Columbia University
MICHAEL CONARD
The Earth Institute, Columbia University
PATRICIA CULLIGAN
The Earth Institute, Columbia University
School of Engineering and Applied Science, Columbia University
RICHARD PLUNZ
The Earth Institute, Columbia University
Graduate School of Architecture, Planning and Preservation, Columbia
University
MARIA-PAOLA SUTTO
The Earth Institute, Columbia University
LEIGH WHITTINGHILL
The Earth Institute, Columbia University
189
Acknowledgements: The authors gratefully acknowledge support for this work from the National
Science Foundation (NSF) grant CMMI-0928604 and the Doris Duke Charitable Foundation.
Leigh Whittinghill also gratefully acknowledges support from an Earth Institute Post-Doctoral
Scholarship. The authors wish to thank the respondents to the informal survey for their time and
Brooklyn Grange Farm for their cooperation with the monitoring work. Any opinions, findings,
and conclusions expressed in this paper are those of the authors and do not necessarily reflect the
views of any survey respondent or supporting agency.
* This paper was presented at the 2013 International Conference on Sustainable Development
Practice (ICSDP) held on September 6-7 at Columbia University, New York.
02 Ackermann et al article_ESRI Vol 45-2 27/06/2014 14:40 Page 189
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Abstract: Populations around the world are growing and becoming predominately urban, fueling
the need to re-examine how urban spaces are developed and urban inhabitants are fed. One
remedy that is increasingly being considered as a solution to inadequate food access in cities, is
urban agriculture. As a practice, urban agriculture is beneficial in both post-industrial and
developing cities because it touches on the three pillars of sustainability: economics, society, and
the environment. Historically, as well as currently, economic and food security are two of the most
common reasons for participation in urban agriculture. Urban agriculture not only provides a
source of healthful sustenance that might otherwise be lacking, it can also contribute to a
household’s income, offset food expenditures, and create jobs. Social facets are another reason for
populations to engage in urban agriculture. A garden or rooftop farm is a place where people come
together for mutual benefit, often enhancing the common social and cultural identity for city
residents. Larger urban farms also participate in community enrichment through job training and
other educational programmes, many of which benefit underserved populations. Finally, urban
agriculture can play an important role in the environmental sustainability of a city. As a form of
green infrastructure, urban farms and community food gardens help reduce urban heat island
effects, mitigate urban stormwater impacts and lower the energy embodied in food transportation.
This paper will describe a multi-year study undertaken by the Urban Design Laboratory at
the Earth Institute to assess the opportunities and challenges associated with the development of
urban agriculture in New York City (NYC). The paper will present metrics on potential growing
capacity within the City inclusive of both rooftop and land-based options, results from a survey of
New York City based urban farmers that gathered information on the challenges and barriers to
food production in NYC, with a focus on rooftop farming, and data from an environmental
monitoring study on a commercial rooftop farm in Brooklyn. The paper will use the results of the
multi-year study to provide insight into the potential role of urban agriculture to creating a more
sustainable food system for New York City and cities elsewhere.
I INTRODUCTION
Populations around the world are growing, projected to increase to 9.3
billion by 2050 (USCB, 2012), and becoming predominately urban. Indeed,
in 2011 the urban population in some of the world’s developed regions,
including the United States (US), surpassed over three-quarters of the total
population (UNDESA, 2012). This growth in urban population is fueling the
need to re-examine how urban spaces are developed and urban inhabitants are
fed. One remedy that is increasingly being considered as a solution to
unhealthy and/or inadequate food access in cities is urban agriculture. Urban
agriculture is usually described as horticultural, agricultural, and farming
activities carried out on small plots of land in and around urban centres,
however some definitions also include animal husbandry (Enete and Achike,
2008; Graefe et al., 2008; Vagneron, 2007). As a practice, urban agriculture
touches on all three pillars of sustainability: economics, society, and the
environment, as described below.
1.1 Economic Benefits of Urban Agriculture
Historically as well as today, community development, food security and
economic security are three of the most common reasons for participation in
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urban agriculture. Urban agriculture not only strengthens social ties and
provides healthful sustenance that might otherwise be lacking, it can also
contribute to a household’s income, offset food expenditures, and create jobs.
Food security is affected by both the quantity and quality of food available
to a household. Even in locations where urban agriculture does not contribute
significantly to employment, food security is of major concern to urban farmers
(Nugent, 2002). Food insecurity, or the lack of access to adequate food for an
active and healthy life (Nord et al., 2007) is not just a problem in the
developing world, but in the United States as well (Enete and Achike, 2008;
Nugent, 2002; Widome et al., 2009). Food insecurity can be temporary or
chronic (de Zeeuw et al., 1999) and is associated with a variety of problems in
adolescents, who are at higher risk than young children (Widome et al., 2009).
A perceived or actual need to improve food security and a lack of ability to rely
of food from rural areas can result in the use of urban agriculture (Graefe et
al., 2008; de Zeeuw et al., 1999), which has been shown to improve the
quantity and quality of food available to low income urban households under
a variety of conditions (Enete and Achike, 2008; Graefe et al., 2008; Nugent,
2002; Widome et al., 2009; de Zeeuw et al., 1999).
The extent to which urban agriculture supplements household income is
diverse and can be dependent on crop choice and the scale of production.
Staples, such as rice, can provide income security for a household (Vagneron,
2007), but vegetables can often command higher market prices (Graefe et al.,
2008; Vagneron, 2007). Animal husbandry can also provide high profits
(Graefe et al., 2008; Nugent, 2002; Vagneron, 2007) through the sale of dairy
products (Nugent, 2002) or manure as fertiliser (Graefe et al., 2008). In some
cases, only excess produce is sold (Graefe et al., 2008; Vagneron, 2007) or
urban agriculture is used to supplement inadequate household incomes (Enete
and Achike, 2008; Nugent, 2002; Vagneron, 2007). In other cases, urban
agriculture may be the only reported source of income for a household and
plays an important role in alleviating poverty (van Averbeke, 2007; Graefe et
al., 2008). For households who do not sell produce, urban agriculture frees up
funds for other uses (van Averbeke, 2007; Enete and Achike, 2008; Nugent,
2002; Vagneron, 2007). This can stretch the household budget, allowing for the
purchase of other essential items (van Averbeke, 2007; Nugent, 2002) or
increase economic freedom for women where household budgets are male-
controlled (van Averbeke, 2007). Job creation through urban agriculture is also
highly variable. In some areas, half of urban farmers employ workers (Graefe
et al., 2008). In others, urban farmers are too poor, or the employment market
too fragmented to provide more than occasional or seasonal job opportunities
(Nugent, 2002).
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1.2 Societal Benefits of Urban Agriculture
Social facets are another reason for populations to engage in urban
agriculture (van Averbeke, 2007; Nugent, 2002). A garden or rooftop farm is a
place where people can come together for mutual benefit (van Averbeke, 2007;
de Zeeuw et al., 1999), often providing a common social and cultural identity
for city residents (van Averbeke, 2007). Urban agriculture is commonly cited
as a means of fostering community empowerment or as an opportunity for
urban residents, particularly in underserved areas, to directly engage with
food production and food procurement, which is increasingly seen as a social
justice issue (Mees and Stone, 2012). Larger urban farms also participate in
community enrichment programmes such as skills development, job training
and other educational programmes, many of which benefit underserved
populations. These programmes use the produce in cooking and nutrition
lessons for residents, as is done at Seeds to Feed Rooftop Farm, in Brooklyn
(SFRF, 2013) or the Growing Chefs programme, which offers educational
programming in farming, gardening and cooking at numerous locations,
including the Eagle Street rooftop farm (Growing Chefs, 2013). Programmes
such as CORE/El Centro in Milwaukee also use urban farming as part of their
healing therapies agenda and to help re-connect immigrant communities to
their cultural roots, which value access to fresh, locally grown produce
(Fredrich, 2013).
1.3 Environmental Benefits of Urban Agriculture
Finally, urban agriculture can play an important role in the environmental
sustainability of a city. As a form of green infrastructure, urban farms and
community food gardens can help reduce urban heat island effects, mitigate
urban stormwater impacts, and lower the energy embodied in food
transportation.
The Urban Heat Island (UHI), defined as higher mean temperatures in an
urban area than the surrounding rural area (Alexandri and Jones, 2008;
Getter and Rowe, 2006; Memon et al., 2008), can lead to urban temperatures
between 0.6˚C and 12˚C warmer than those of surrounding rural areas
(Cheval, et al., 2009; Memon et al., 2010). Increasing the amount of vegetation
in an urban area is one of the more popular methods of mitigating the UHI
through altering the heat balance of a city (Akbari, 2002). Shading by
vegetation blocks and redistributes incoming solar radiation and diffuses light
reflected from nearby urban surfaces (Akbari, 2002; Alexandri and Jones,
2008) that would otherwise be reflected or re-radiated as sensible heat by
urban surfaces (Memeon et al., 2008). Evapotranspiration in vegetated areas
acts as a heat sink and also results in lower ambient and surface temperatures
than urban areas without vegetation (Akbari, 2002; Alexandri and Jones,
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2008; Getter and Rowe, 2006). Unfortunately, many urban areas do not have
much ground level land for additional green space, leaving rooftops as an
important space for greening. Rooftop farms can help reduce local
temperatures (Wong et al., 2007) and when implemented on a city wide scale,
could result in significant cooling of the urban environment (Bass et al., 2003).
Urban vegetation, including agricultural space, can also be used in
stormwater management. Its effectiveness at reducing stormwater runoff
quantities and improving runoff quality is dependent on a number of factors.
Green roofs can retain between 52.3 and 100 per cent of precipitation,
reducing the amount of stormwater runoff (Czemiel Berndtsson, 2010; Getter
et al., 2007; Hathaway et al., 2008; Rowe, 2011; VanWoert et al., 2005). This
has garnered them attention in municipal policy in cities such as Portland,
Oregan (Liptan, 2005) as well as NYC. The ability of green roofs to improve
runoff water quality is less clear. Green roofs release lower concentrations of
heavy metals in runoff water than non-vegetated roofs (Czemiel Berndtsson et
al., 2006; Czemiel Berndtsson, 2010; Rowe, 2011), but have mixed
performance with respect to nutrients, such as nitrogen and phosphorus
(Czemiel Berndtsson et al., 2006; Hathaway et al., 2008). Fertiliser application
to green roofs only increases the levels of nutrients in runoff (Czemiel
Berndtsson et al., 2006; Emilsson et al., 2007; Rowe et al., 2006). The effect of
fertiliser on runoff water quality is one of the important environmental issues
associated with rooftop agriculture and it is yet to be fully understood
(Whittinghill and Rowe, 2012).
Urban agriculture can also lower the energy embodied in food
transportation by reducing the number of miles food has to travel from the
farm to the table. It has been estimated that food typically travels about 1,300
miles (2,080 km) from farm to table, a figure which could be reduced to 30
miles (49 km) for some foods if they were produced more locally (Peters et al.,
2009). Additionally, decreasing the distance that food travels can have a
significant impact on reducing spoilage and therefore food waste; preliminary
analysis has indicated that from an embodied energy perspective, decreasing
food waste may be a more significant benefit of highly localised food
distribution than fuel use (Ackerman et al., 2012). Urban agriculture may also
improve nutrient cycling through local recycling and re-use of organic and
water wastes (de Zeeuw et al., 1999), thereby reducing the ecological footprint
of urban centers (Peters et al., 2009; de Zeeuw et al., 1999). Many rooftop
farms rely on compost that is made from locally collected food scraps,
including the Brooklyn Grange described in Section 2.3 (Ben Flanner, personal
communication, May 24, 2012). In some cases, such as the Intercontinental
New York Barclay hotel, these are food scraps from the kitchen of the building
on which the farm is located (IHR, 2013).
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II URBAN AGRICULTURE AND NEW YORK CITY
To provide insight into the potential role that urban agriculture could play
in creating a more sustainable food system for today’s evolving cities, the
Urban Design Lab (UDL) at Columbia University’s Earth Institute has
undertaken a multi-year study of urban agriculture potential in New York
City (NYC). The study has examined the food production capacity within the
City (Ackerman et al., 2011) as well as the challenges and barriers to urban
faming, with an initial focus on rooftop farming. In addition, the study has
undertaken some initial quantification of the environmental benefits and
impacts of urban farming, again with an initial focus on rooftop farming.
Findings to date in each of these areas are reported below.
2.1 Potential Food Production Capacity Within New York City
Understanding the capacity of urban agriculture to feed urban
populations necessarily hinges on estimations of how much food can be grown
within a city area. This is a critical assessment, in that the viability of urban
agriculture and the degree to which it is afforded political and cultural support
is, to some extent, dependent on perceptions of whether it can have a
significant impact on local food availability and security.
In New York City, urban agriculture is already contributing to improved
food security in many neighbourhoods. Community gardens across the city are
providing food to members and supplying local food banks with their produce.
Researchers at the Farming Concrete project estimated that 87,690 lbs of
vegetables were grown on 67 gardens of the city’s hundreds of community
gardens in 2010 (Gittleman 2010). Urban farms such as Added Value Red
Hook and East New York Farms have Community Supported Agriculture
(CSA) programmes offering produce Potential food production capacity within
New York City from their farms, while Eagle Street Rooftop Farm has a CSA
which is supplemented with produce from a farmer in the Hudson Valley (this
may be the first CSA in the nation to be at least partially supplied by a rooftop
farm). Farms and community gardens are also selling their produce at farmers
markets, in some cases onsite (such as with Added Value Red Hook, East New
York Farms, La Finca Del Sur, Hattie Carthan Community Garden, and
others), and the City is partnering with Just Food to establish five more
farmers markets at community gardens. Many of these farmers’ markets also
host regional producers from outside the city. These examples provide
evidence of how urban agriculture is acting as a catalyst for larger food system
change by providing facilities and logistical support for regional producers to
gain access to urban consumers. Many of these community farmers markets
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are in areas where conventional grocery stores are reluctant to locate due to
concerns about neighbourhood income levels and demand.
To up-scale current urban agricultural activities to the point where NYC
might be self-sufficient in supplying its fruit and vegetable needs, research by
the paper’s authors indicates that between 162,000 and 232,000 acres of land
are needed (Ackerman et al., 2011). This figure does not account for the
approximately 886 million lbs of tropical or warm-weather fruit consumed
annually by New Yorkers, which cannot be grown locally (these warm-weather
products represent 64 per cent of total annual fruit consumption by weight
and 24 per cent of combined total annual fruit and vegetable consumption by
weight). If all of the potentially suitable vacant land in the city (estimated at
4,984 acres) were converted to urban agriculture with an average growing
area of 70 per cent of the lot area, the research estimates that this could
supply the produce needs of between 103,000 and 160,000 people – depending
on whether conventional or biointensive food yield figures are used. Although
this is a substantial number of people, it falls well short of the population of
NYC. Thus, while there is much more land potentially available than simply
vacant lots, it is clear that NYC cannot strive to be anywhere close to self-
sufficient in supplying its fruit and vegetable needs, much less all foods.
Although urban land availability precludes non-warm weather fruit and
vegetable self-sufficiency for NYC, Ackerman et al. (2011) do show that for
specific high value, healthy crops suited to urban farming, localised production
is actually feasible from the perspective of land availability. While crops such
as beans and potatoes need a great deal of land area and are not particularly
well suited to small-scale, urban production, crops such as leafy greens and
tomatoes may be grown in large quantities in urban areas. For dark green
vegetables, for example, only 8,671 acres are needed to supply NYC using
biointensive growing methods, and the approximately 360 million pounds of
tomatoes consumed annually by New Yorkers could be grown on 8,260 acres.
Furthermore, considerably less area would be needed for these vegetables to
be grown hydroponically.
Considering the needs and resources of particular communities within
NYC also adds a different dimension to the analysis. There are a number of
NYC neighborhoods where a confluence of factors makes urban agriculture a
particularly attractive and effective means of addressing multiple challenges.
These include low access to healthy food retail, high prevalence of obesity and
diabetes, low median income, and comparatively high availability of vacant
and other available land. Not coincidentally, these factors are all correlated,
and it is in these areas where urban agriculture could have the greatest
impact on food security.
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New York City neighbourhoods which fit the pattern of inadequate healthy
food access, high incidence of diet-related disease, greater percentage of
vacant land, etc., were found to include East New York, Brownsville, Crown
Heights, Bedford-Stuyvesant, and Bushwick in Brooklyn, the Lower East Side
and East and Central Harlem in Manhattan, and Morrisania, Claremont
Village, East Tremont, and Belmont in the Bronx, among others. These are
also neighbourhoods where the presence of many community gardens signifies
community interest in and engagement with food production. In these
neighbourhoods, urban agriculture could improve fresh food availability. For
example, Brooklyn Community district 16 (Brownsville) has 58 acres of vacant
land, which, if converted entirely to vegetable production, could produce as
much as 45 per cent of the district’s 85,000 residents’ annual supply of dark
green vegetables (broccoli, collard greens, escarole, kale, lettuce leaf, mustard
greens, spinach, and turnip greens; this estimate assumes an average lot
coverage of 70 per cent for growing area). This district also has an estimated
23 acres of green space on New York City Housing Authority (NYCHA)
property, as well 14 acres of surface parking – converting some of this area to
farming or gardening could increase the availability of fresh produce even
further.
2.2 Challenges and Barriers to Food Production in New York City
The capacity of urban agriculture to meet certain food needs within a city
also hinges on the ease at which urban faming can be practiced. To develop a
better understanding of the challenges and barriers facing urban farmers, and
to evaluate whether changes to policy or other systemic conditions could help
alleviate such barriers, the UDL undertook a survey of NYC based farmers.
The survey was informal and was administered to 22 individuals who are
active in rooftop farming and gardening in NYC. Respondents were asked to
identify challenges and barriers to the development phase (planning, design,
construction) of a rooftop farm or garden, how they addressed these
challenges, and whether they could think of broader solutions that would help
mitigate or alleviate these challenges for them or other prospective farmers in
the future. They were then asked a similar series of questions regarding the
operation of rooftop farms and gardens (encompassing farm management,
maintenance, etc.). This structure allowed for the differentiation between the
barriers to entry for prospective rooftop farmers and gardeners, as opposed to
the challenges encountered once a farm or garden has already been
established – a distinction which was deemed to be important to identifying
how potential policy incentives or solutions might best be targeted.
Participants were free to identify as many challenges as they wished, as they
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were not asked to create a hierarchy; although some did so of their own
volition, specifically referring to some issues as “primary,” “the major
problem,” etc. Questions were left open-ended and follow-up questions were
asked for clarification. Results were then transcribed, reviewed, and compiled,
and common themes were identified.
Survey participants were identified using a variety of sources, including
existing UDL contacts, the greenroofs.com database (GRC, 2013), and public
information on recipients of tax incentives and green infrastructure grants.
These individuals included 20 people with experience in the rooftop farming
development process, which includes the planning, design, and construction
phase, 7 people who have an oversight, management, or maintenance role on
an active rooftop farm or garden, and 10 active rooftop farmers or gardeners
(with many of the individuals filling multiple roles). Collectively, respondents
participated in the development and/or operation of 13 rooftop farms and 19
rooftop gardens with a total growing area of over 150,000 square feet and a
median growing area of 1,000 square feet (and with a total of approximately
100,000 additional square feet in the planning phase). Of the roofs, 13 use an
intensive green roof system, 3 are extensive, while 15 involve some form of
container farming or gardening (with some roofs including more than one
type). Of these operations, 3 are in the Bronx (total 11,000 square feet), 11 in
Manhattan (10,275 square feet), 14 in Brooklyn (86,400 square feet), and 2 in
Queens (47,000 square feet) (none of the roofs are in Staten Island). Of the
roofs, 4 are commercial rooftop farms, generating revenue primarily from sales
to retailers, restaurants, and through farm stands and CSAs; 7 are projects on
residential buildings intended primarily for use by multiple building
occupants; 3 are non-profit operations staffed by volunteers supplying shelters
or kitchens, 4 are on schools and meant primarily for educational purposes, 6
are on restaurants or hotels and used to supply commercial kitchens, and 6 are
on private residences. Given the fact that rooftop farming and gardening is not
a widespread activity in NYC, the study that was undertaken is believed to be
fairly representative of this small but growing community. This is because a
majority of rooftop food producing sites in NYC are in some way represented
by the respondents, whether through people involved in design and
construction or those who are responsible for day-to-day operations.
The range of topics raised by the survey respondents included: Regulation
and Permitting; Tax Incentives; Green Infrastructure Grants; Rooftop Farm
Siting; Funding; Roof System and Growing Media; Farm Maintenance and
Labour; Access to Equipment and Materials; Climate and Pests; Information
and Knowledge Dissemination on Best Practices; Community Outreach and
Involvement. This wide range of topics is an indication of the complexity of
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rooftop food cultivation and the many challenges farmers encounter in their
efforts to develop a successful operation. Nonetheless, the barriers mentioned
in the survey can be broadly organised into four nested categories: at the
highest level, rooftop farmers identified challenges that have to do with
starting a small business in NYC, which many other types of businesses may
face, such as securing loans and managing costs and labour requirements. The
second category of challenges involves issues faced by small farmers generally,
and includes such things as pest management and developing a viable
marketing or distribution plan. The third category is specific to urban
agriculture, incorporating the opportunities and constraints inherent in
growing food productively in a dense urban setting. The last category,
encompassing the majority of the problems identified, is specific to rooftop
agriculture. These challenges included finding an appropriate site, securing
the proper permits, financing construction, and managing and operating a
farm or garden. Rooftop farms are both green roofs and farms, and some
are commercial businesses while also attempting to demonstrate larger social
and environmental benefits. These goals do not easily coincide, and many
of the problems raised had to do with determining how to navigate this
difficulty.
2.3 Environmental Monitoring of a Commercial Rooftop Farm in Brooklyn,
NYC
Financing the construction of a rooftop farm, especially a larger facility
that has the potential to become commercially viable, was raised as a key
concern by responders to the survey discussed above. Green infrastructure
grants or tax incentives are both means via which rooftop farmers might
access necessary finance, provided it can be demonstrated that rooftop farms
have environmental benefits, most especially with respect to stormwater
management. To date, however, few studies have quantified the impact of
green roof farming practices on stormwater management issues, leading to
lack of clarify on whether rooftop farms are even eligible for certain grants or
tax incentives.
In order to address current lack of information on the environmental
performance of urban rooftop farming, the UDL is engaged in monitoring the
Long Island City Brooklyn Grange rooftop farm located at 37-18 Northern
Boulevard. The rooftop farm was installed in 2007 and uses Rooflite
®
green
roof media (Skyland USA LLC, Landenberg, PA) mounded into rows with a
depth of 20-25 cm (8-10 in) and 2.5-5 cm (1-2 in) between row depth. The farm
covers almost all of the 3,716 m
2
(40,000 ft
2
) rooftop. A 281 m
2
(3,022 ft
2
)
watershed located centrally on the northern side of the building was selected
for instrumentation to measure stormwater runoff quantity, while a second
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drainage basin located on the north-west corner of the farm was selected to
monitor runoff quality. Non-vegetated areas of the roof include a stairwell, the
central roof walkway made of gravel, and walkways between crop rows. The
green roof is planted with vegetables, herbs and some flowers for cutting,
including sunflowers. Irrigation is supplied to the plants through a drip
irrigation line 3 times daily for 30-40 minutes, depending on weather
conditions. Monitoring for water quality runoff at the farm began in January
2013, while monitoring for runoff quantity began in May 2013.
Preliminary results from the monitoring programme have focused on
examining the water quality of runoff from the rooftop farm. Runoff water
quality is determined from samples collected during individual storm events
as runoff enters a rooftop drain. Rain water from the same storm is also
collected for comparative purposes. To date, one irrigation water sample has
also been gathered. After collection, the samples are taken back to the Heffner
Laboratory at Columbia University and analysed for pH and electrical
conductivity with an Accumet
TM
excel XL50 duel channel pH/ion/conductivity
meter (Fisher Scientific, Hampton, NH), turbidity with a 2020we turbidity
meter (LaMotte, Chestertown, MD), and colour and true colour with a DR/890
colorimeter (Hach, Loveland, CO). A portion of each sample is also stored in a
freezer and will later be sent to Auburn University Soil Testing Laboratory
(Auburn University, AL) for nutrient content analyses, including nitrogen and
phosphorus.
Thus far, a total of 20 samples have been taken for water quality analysis.
To compare the environmental impacts of the farm with that of a conventional
green roof, the Brooklyn Grange water quality data were compared to data
obtained from prior work that examined the quality of runoff from extensive
sedum green roofs, as well as traditional non-vegetated roofs, installed on a
variety of NYC buildings (Culligan et al., 2013). Comparative findings to date
are summarised in Figures 1 to 4.
The average pH of runoff from the Brooklyn Grange is slightly higher than
that of rain from Manhattan and lower than that of rain from the Brooklyn
Grange or runoff from the extensive sedum green roofs (Figure 1). The
conductivity (Figure 2) and apparent colour (Figure 3) of runoff from the
Brooklyn Grange are much higher than all other water sources, which are
similar to each other. Sample true colour follows the same pattern (not shown).
The average turbidity of runoff from the Brooklyn Grange appears higher than
that of either rain source, but similar to runoff from both non-vegetated and
extensive sedum green roofs (Figure 4). That runoff from the Brooklyn Grange
has higher conductivity and true colour than runoff from conventional green
roofs might indicate poorer runoff quality from the rooftop farm than a sedum
green roof.
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Figure 1: Average pH of water sampled from Brooklyn Grange runoff (BKG),
Brooklyn Grange irrigation (Irrigation)*, rain from a Manhattan Building
(Rain121) and rain from the Brooklyn Grange (RainBKG). Runoff
measurements from traditional non-vegetated roofs (non-vegetated), extensive
sedum green roofs (green) and rain (rain) samples were collected from a
previous study (Culligan et al., 2013).
Figure 2: Average conductivity of water sampled from Brooklyn Grange
runoff (BKG), Brooklyn Grange irrigation (Irrigation)*, rain from a
Manhattan Building (Rain121) and rain from the Brooklyn Grange
(RainBKG). Runoff measurements from traditional non-vegetated roofs (non-
vegetated), extensive sedum green roofs (green) and rain (rain) samples were
collected from a previous study (Culligan et al., 2013).
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SUSTAINABLE FOOD SYSTEMS FOR FUTURE CITIES 201
Figure 3: Average apparent colour of water sampled from Brooklyn Grange
runoff (BKG), Brooklyn Grange irrigation (Irrigation)*, rain from a
Manhattan Building (Rain121) and rain from the Brooklyn Grange
(RainBKG). Runoff measurements from traditional non-vegetated roofs (non-
vegetated), extensive sedum green roofs (green) and rain (rain) samples were
collected from a previous study (Culligan et al., 2013).
Figure 4: Average turbidity of water sampled from Brooklyn Grange runoff
(BKG), Brooklyn Grange irrigation (Irrigation)*, rain from a Manhattan
Building (Rain121) and rain from the Brooklyn Grange (RainBKG). Runoff
measurements from traditional non-vegetated roofs (non-vegetated), extensive
sedum green roofs (green) and rain (rain) samples were collected from a
previous study (Culligan et al., 2013).
02 Ackermann et al article_ESRI Vol 45-2 27/06/2014 14:40 Page 201
III CONCLUSIONS AND RECOMMENDATIONS
There are distinct opportunities and challenges inherent in urban
agriculture in NYC, which is the highest-density US metropolis with some of
the nation’s highest land values, making the prospect of farming in the five
boroughs a demanding proposition. On the other hand, NYC has particular
advantages: the economic and cultural robustness that serve to maintain high
property costs are also associated with a high level of awareness, support and
potential access to investment capital for projects that promote healthy food
systems and sustainability. Specifically, urban farms are uniquely dependent
on their surrounding communities to provide a strong customer base, and
NYC’s density, and diverse and vibrant food culture make for an attractive
context for aspiring urban farmers. NYC’s industrial and manufacturing areas
are also highly suitable for rooftop agriculture due, in part, to access to re-
development capital, a robust transportation network and adequate physical
infrastructure. And despite what some might assume to be an inhospitable
climate for agriculture, NYC’s five boroughs have a rich farming history, with
Queens and Kings Counties being among the most productive agricultural
counties in the nation in the late 19th century, all before the advent of
advanced season-extension techniques (Linder and Zacharias, 1999). In
Manhattan, for several decades in the 19th century, the extensive squatter
settlements were said to produce a large proportion of the produce consumed
by the city (Plunz, 1990). Indeed, as with other urban areas, the demise of
localised production only began with the advent of modern food transport
technologies such as refrigerated rail boxcars, interstate trucking, and air
freight, which successively promoted the nationalisation and then the
globalisation of the food system.
Urban agriculture has great potential to help mitigate critical public
health and environmental problems faced by NYC. The city suffers from
higher than average rates of obesity and diabetes (Raufman et al., 2007),
which are correlated to inadequate access to fresh, healthy food retail
(Morland et al., 2006). This is relevant to the issue of urban agriculture
because, as discussed in Section 2.1, the communities that suffer the most
from diet-related disease and inadequate access to healthy foods are also the
areas where much of the city’s vacant land is located.
Urban agriculture is also part of a broader range of horticultural
strategies that involve the creation of productive green space to directly
address some of NYC’s most intractable environmental problems, including
those associated with urban stormwater management (Carson et al., 2013)
and mitigation of the urban heat island effect. Additionally, urban agriculture
could decrease the environmental and economic costs of dealing with the City’s
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02 Ackermann et al article_ESRI Vol 45-2 27/06/2014 14:40 Page 202
waste stream by providing alternative means of disposing of organic waste
through composting. Although urban farms could realistically process only a
small percentage of NYC’s compostable waste, as with other issues, the value
lies in their potential as a catalyst for promoting shifts in consciousness and
behaviour that could greatly amplify such, otherwise modest, impacts.
The solutions that urban agriculture offers to multiple problems in NYC,
as discussed in this paper, are likely to be similar to those in other cities
around the world, as are the hurdles to urban agriculture implementation.
The work conducted by the authors of this paper indicates that these hurdles
require urban policy amendments that would make it easier for urban farmers
to obtain permits and undertake practices such as large-scale composting at
their facilities, as well as further research that could lead to the development
of best urban farming practices, including practices that reduce nutrient
loading in the runoff from urban farms. Development of urban agricultural
extensions at urban university centres is one way of cultivating the knowledge
and expertise that could maximise the value of urban agriculture for city
inhabitants.
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