The Case for Urban Agriculture as a Driver of Environmental Sustainability

Abstract

As a result of the growing global population, many cities around the world are experiencing rapid urbanization. With that comes a growing demand for food and increasing challenges in food production. One solution increasing in popularity is urban agriculture (UA), simply defined as the production of food in an urban environment. UA can operate on different scales (micro, meso, and macro) have various objectives (recreational, subsistence, or commercial), and take place across landscapes in the form of backyard gardens, community gardens, rooftop gardens, aquaculture, agroforestry, allotment gardens, as well as urban beekeeping.

For many cities, UA represents a solution to several urban problems including derelict vacant land, economic underdevelopment, and lack of access to healthy food. However, UA also provides significant contributions to urban biodiversity and offers important ecosystem services such as pollination and climate control. This study examines how the implementation of UA positively affects urban biodiversity and essential ecosystem services, as opposed to leaving these often-abandoned city spaces untouched. The methodology used for this study included comprehensive literature reviews and independent observation of a local community garden. The primary goal of this paper is to show that implementing urban agriculture can provide unmatched environmental benefits to previously vacant urban spaces.

Introduction

Urbanization is considered one of the most significant anthropogenic alterations of the environment (Patra et al., 2018) that also affects the socioeconomic landscape. According to the United Nations, 55% of the world's current population lives in urban areas and is expected to increase to 68% by 2050. The combined effects of global population growth and urbanization, or people moving from rural to urban areas, could result in 2.5 billion more people living in cities by 2050 (United Nations, 2018). The many impacts of urbanization on the environment include an increase in air temperature, changes to water cycles and ecological processes that change the functions that food-producing ecosystems depend on (Andersson, 2006). Biodiversity and agriculture are inextricably linked. Genetic diversity is the basis of ecosystem services essential to sustaining agriculture and human well-being. At the same time, agriculture can drive conservation efforts and promote sustainable use of biodiversity (URBES, 2014). While urban agriculture (UA) has gained steam in cities' responses to food security issues (Lin et al., 2015), cities also play important roles in conserving biodiversity, particularly through planning and management of urban green spaces (Aronson et al., 2017), as these spaces are increasingly becoming important refuges for native biodiversity (Goddard et al., 2010).

Human activities have caused an estimated 1.0ºC of global warming above pre-industrial levels with significant implications for biodiversity and ecosystems, including species loss and extinction that puts their functions and services to humans at risk (IPCC, 2018). Food security depends on functioning ecosystems. As we continue to suffer the effects of climate change, protecting and promoting biodiversity in our agricultural systems will be essential to making global food systems "more adaptable and resilient" and in securing the ecosystems services humans depend on (URBES, 2014). Thus, in addition to improving access to healthy food, UA contributes ecosystem benefits such as pollination, energy conservation, reducing storm water runoff, and helping control urban climate (National Science Foundation, 2018). These benefits are gained for previously vacant spaces, thus, rendering those implemented with UA far more beneficial to the urban landscape. In the search for productive uses of vacant lots, developing the local economy, creating jobs, improving the natural environment with the added benefit of contributing to the environmental sustainability of cities, support for UA is building across the U.S. (Baltimore Office of Sustainability, 2013).

More specifically, in my hometown of Baltimore, MD, city leadership has recognized that UA can provide solutions to a wide range of problems and therefore supports numerous projects throughout the city by continuously establishing new policies to promote UA's development and implementation. In addition, many government agencies and partners offer assistance and critical resources to support the projects (Baltimore Office of Sustainability, 2013). Projects in the city of Baltimore include urban farms, community gardens, school gardens, home and rooftop gardens, aquaculture projects, apiaries, and orchards. One such project, the Blue Jay's Perch, is a Johns Hopkins University initiative that enables students, faculty, staff, and community members to collaborate on an environmentally sustainable food production system (JHU Community Garden, nd). This community garden provides locally grown food within Baltimore and also promotes environmental sustainability.

Urban agriculture is the collective name for a wide variety of farming activities that take place within city boundaries (Aerts et al., 2016). Ideally, urban agriculture (UA) connects people, environmentally sustainable cultivation methods, and the local economy to create healthy local food systems, strong communities, and ensures the availability of nutritious food and ecosystem services while increasing urban food security (URBES, 2014). UA activities are quite diverse and can include cultivating vegetables, medicinal plants, spices, fruit trees, and ornamental plants, as well as livestock for eggs, milk, meat, and wool (Lovell, 2010). However, this is infrequent due to concerns of pollution and infectious diseases like salmonella (Pollock et al., 2012).

In densely populated cities, space is at a premium (Burchard-Dziubinska, 2014). Cities are facing many challenges including issues with air and water quality, insufficient green space, urban heat islands, polluted storm water runoff, and diminished ecological biodiversity (Knizhnik, 2012). Industrialized cities are “eager to include UA into their food policies as part of their efforts to become ‘climate neutral’” (Aerts et al., 2016). However, there are four main reasons for growing food in cities: subsistence, economics, recreation, and community building (Hallett et al., 2017).

Depending on the reason for urban food production, UA can take many forms. There are rooftop gardens, described as any gardens established on the roof of a building used for decoration or agricultural purposes (Lin et al., 2015). Allotment gardens are plots of land divided up and assigned to individuals for non-commercial food growing and recreation. Similarly, community gardens are plots of land that people cultivate together (Aerts et al., 2016). Community farms are communal growing spaces that engage the surrounding community in small-scale food production (URBES, 2014). Container gardens are an array of containers in which vegetables are grown. Backyard gardens are private plots of land cultivated by individuals. Hydroponic systems are greenhouse agricultural systems that don’t use soil but instead intensively reuse irrigation water and nutrients. Rooftop farms are vegetable farms that use containers, raised beds, hydroponic systems, or soil put on the roof of a building. Windowsill farming is growing vegetables in containers on windowsills or balconies (Aerts et al., 2016). Urban orchards are tree-based community food production systems. Additionally, UA systems can fit into more than one category. For example, backyard gardens and community gardens can be rooftop gardens while orchards can sit inside community gardens (Lin et al., 2015).

Urban gardens combine “utility, recreational benefits, social meaning, aesthetic beauty, and many ecosystem services” (URBES, 2014). UA provides ecosystem services that are grouped into four categories: provisioning services, that is, human benefit from nature like food, drinking water, timber, wood fuel, natural gas, oils, and plants for other uses like medicine; regulating services or benefits, such as pollination, climate control, erosion and flood control, carbon sequestration and storage, and waste water treatment; cultural services, or non-material benefits that connect people to their spaces; and supporting services, which the basis of all ecosystems and their services that include habitat for species and genetic diversity maintenance, photosynthesis, nutrient cycling, soil creation, and the water cycle (The National Wildlife Federation, nd). Figure 1 details the ecosystem services provided by UA.

One of the most important ecosystem services provided by UA is pollination. Over 80% of flowering plants depend on pollinators such as birds, bats, butterflies, beetles, hover flies, wasps, moths, and bees (United States Department of Agriculture, nd; Xerces Society for Invertebrate Conservation, 2017). Collectively, pollinators contribute to healthy, productive plant communities, provide food for wildlife, and play a critical role in crop production (Xerces Society for Invertebrate Conservation, 2017). Hence, the loss of these species has a major impact on food production and environmental health as “ecological interactions between plants and pollinators provide critical ecosystem services and are important drivers of biodiversity and community function” (United States Department of Agriculture, nd). UA can be a significant means of providing “wildflower-rich habitats to support pollinators and promote local biological diversity” by supplying shelter and food for wildlife while being highly attractive to pollinators (Xerces Society for Invertebrate Conservation, 2017).

In addition to the obvious benefit of providing food, UA is an effective way of using vacant lots to support biodiversity and enhance ecosystem services (URBES, 2014). UA is an “opportunistic use of vacant land” (Clinton et al., 2017), cutting down on vacant abandoned land that contributes to neighborhood decay, reduced property values, attracts crime, vagrancy and rodent infestation (Baltimore Office of Sustainability, 2013). Left empty, city lots can become dumping grounds that can lead to spills of potentially toxic substances that cause soil and groundwater contamination. Additionally, vacant lots typically have poor quality tightly compacted soil that impedes storm water absorption and leads to increased runoff. Similarly, urbanization is considered one of the leading causes of species endangerment as a result of significant changes to the environment that result in “habitat fragmentation, modifications of light and moisture systems and many invasive species” (Knizhnik, 2012).

Increasing species biodiversity in cities can be beneficial for ecosystems as well as human health by improving quality of life through clean air and water, and fertile soil (Knizhnik, 2012). UA offers many improvements to the natural environment and human health, but are not limited to:

• Urban compost systems minimize communities’ waste by transforming it into enriched soil, which increases the productivity of farms or gardens.
• To reduce waste, packaging for locally produced and distributed food is minimized.
• Soil structures and plant root systems can be improved for better storm water run-off absorption. This action reduces the burden on wastewater treatment plants and minimizes contamination of groundwater and waterways.
• Plant foliage reduces carbon dioxide, lowers ozone concentrations, and decreases urban mass temperatures caused by vehicle and industrial emissions.
• The microclimate can be regulated by controlling humidity, lowering summer temperatures, and creating shade.
• Urban biodiversity can be increased by creating habitats for and attracting beneficial soil microorganisms, insects, birds, reptiles, and animals. These spaces can also play a role in species preservation by providing food, protection, and resting spaces along migratory flight paths of birds and butterflies.
• Demands on irrigation can be reduced with hydroponic systems.

(Bellows, 2015; Brown & Carter, 2003; Deelstra and Girardet, 2000; Brown & Jameton, 2000; Okvat & Zautra, 2011; Homegrown Baltimore: Grow Local, 2013; Akbari et al.; Hallet et al., 2017).

In October 2018, the Intergovernmental Panel on Climate Change released a Special Report on the “impacts of global warming of 1.5oC above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty.” The key findings of the report, based on the assessment of available scientific, technical, and socio-economic literature, show that the warming from anthropogenic emissions from the pre-industrial period to the present will persist for many years, continuing to cause even more long-term climate changes. The report proposes that future climate-related risks, such as impacts on biodiversity and ecosystems (including species loss and extinction), would be reduced by the “up-scaling and acceleration of far-reaching, multi-level and cross-sectoral climate mitigation and by both incremental and transformational adaptation” (Intergovernmental Panel on Climate Change, 2018). Implementation of Urban Agriculture (UA) can help in cities’ “mitigation and adaptation efforts to climate change” (Jules et al., 2005). Specifically, UA contributes to the environmental sustainability of cities by:

• Decreasing the 1,300 miles that food travels from “field to plate” to get to consumers (more fuel-efficient and less polluting), which also minimizes food waste.
• Providing food to cities using less energy, thus producing fewer climate change-inducing greenhouse gas emissions.
• Sequestering carbon and reducing atmospheric carbon, which contributes to climate change.

The benefits of UA are not just local. When looked at collectively, UA's benefits are global and enormous. A recent study, funded by the National Science Foundation (NSF) and led by Arizona State University (ASU) and Google researchers, examined the potential gains from transforming unused urban spaces into multifunctional green spaces (Clinton et al., 2018). The researchers used a data-driven approach to quantify the ecosystem benefits of UA (National Science Foundation, 2018). They estimated the potential global benefit of 100-180 million tons of food production, 100,000-170,000 tons of nitrogen sequestration, 14-15 billion kilowatt-hours of energy savings, and 45-57 billion cubic meters of avoided stormwater runoff annually. All told, by analyzing global human population numbers, urban terrain, Food and Agricultural Organization (FAO) datasets in Google Earth Engine, and aggregating the data by country (National Science Foundation, 2018), the research estimated the value of food production, nitrogen fixation, energy savings, pollination, climate regulation, soil formation, and biological control of pests stemming from intense implementation of UA could be worth between $80-$160 billion (Clinton et al., 2018). The researchers conducted this work to provide a framework for local stakeholders to further develop urban agricultural landscapes by using the open data and code included in the paper to determine whether and how much UA can provide for their communities (National Science Foundation, 2018).

Table 3 from the study shows the aggregate economic benefits of ecosystem service values of UA, including food production, nitrogen fixation, energy savings, biocontrol, climate regulation, and soil formation. Overall, the results indicated that existing vegetation provides about $33 billion in services from biocontrol, pollination, climate regulation, and soil formation alone (Clinton et al., 2017).

(Note: MCD12Q1 is the short name for the MODIS Land Cover Type product that provides data characterizing five global land cover classification systems. Additionally, it provides a land-cover type assessment, and quality-control information [Land Processes Distributed Active Archive Center, 2014]. Landscan is a community standard for global population distribution data [Oakridge National Laboratory, nd]).

Over the last decade or two, I have personally witnessed the surge of UA throughout Baltimore city. Though UA has a long history in Baltimore, it has increasingly been utilized to address a wide range of problems. The first "beautification garden" in Baltimore was established in the early 1900s when a vacant lot used for dumping trash was transformed into an allotted garden space for designated families to grow vegetables (Harlean, 1914). Today, the city's leadership has expanded and supports UA to build stronger, healthier communities through the productive use of vacant space while promoting environmental sustainability. In 2009, the Baltimore Sustainability Plan was adopted as a community-responsive sustainability agenda for Baltimore that seeks to increase the availability of fresh produce close to consumers, develop the local economy and create jobs, improve the natural environment, and contribute to the city's environmental sustainability by productively using vacant lots (Baltimore Office of Sustainability, 2013).

One of Baltimore’s UA efforts exists on the campus of Johns Hopkins University at Eastern. The Blue Jay’s Perch is a community garden constructed by university members for faculty, staff, and community members "to learn, teach, and practice safe and environmentally sustainable food production methods" (Blue Jay’s Perch, n.d.). On the occasions that I personally visited the garden this fall, I was able to observe the garden’s corps of volunteers preparing the site for winter. A helpful student volunteer, Ali, was on hand to show and explain to me the garden’s use of cover crops for the winter, including pokeweed, hyacinths, aster, and mint. Other aspects of the site include a pollinator garden and lavender for the bees, a bug house for flies and moths, and fruit trees that still bore a few figs. In the growing season, the garden harvests strawberries, tomatoes, cucumbers, and a variety of greens. Witnessing the workings of the garden firsthand, it became evident that not only does it provide food and recreation for the Johns Hopkins community, but it also serves a larger purpose of contributing to the environmental sustainability efforts of the university and the city of Baltimore.

Conclusion

From the review of current literature and independent observation, this study concludes that urban agriculture is an effective use of often unused and/or abandoned city space that provides numerous social, economic, and particularly environmental benefits. The literature reviews and independent research for this study found the following environmental benefits of UA:

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• Promoting biodiversity
• Enhancing ecosystem services
• Improving air quality
• Contributing to climate control
• Reducing net carbon emissions
• Reducing waste
• Reducing storm water runoff

These findings suggest that implementing urban agriculture in unused city spaces is more effective and provides numerous environmental benefits, rather than leaving the space vacant.

References

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