How to Study the Ecology of Food in the City: An Overview of Natural Science Methodologies

Theresa Wei Ying Ong1* and Gordon Fitch2

  • 1 Program in Environmental Studies, Dartmouth College, Hanover, NH USA
  • 2 Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor USA * Corresponding author Email: This email address is being protected from spam bots, you need Javascript enabled to view it

KEY WORDS: Urban agriculture, natural science methods, review, urban agroecology, urban ecology

A Focus on Ecology

Research in urban agriculture (UA) tends to focus on its very important social aspects (Guitart et al. 2012, Lin et al. 2015). This is likely because UA is clearly a socio-ecological system, which is defined as a system composed of bio-geo physical and social actors and institutions that interact and adapt to one another (Ostrom 1990. Glaser et al. 2008). Agroecology itself is an interdisciplinary field that positions itself squarely in the middle of the social and ecological disciplines, though many argue that the field moves too far in one direction or the other (Gliessman 2014. Rosset and Altieri 2017). An agroecology for urban systems may find itself pulled even further in the direction of society given the central role of the human-dominated landscape. As such, the ecological component of agroecological research, particularly in UA. remains nascent (Guitart et al. 2012. Epstein et al. 2013). Though there has been a recent explosion of interest in UA, a quick search on web of science of “urban+gardens” reveals only 62 articles in the “Ecology” category, the majority of which were published in 2014-2019 and do not necessarily include natural science methods. A similar search for “urban+agriculture” reveals only 91 ecology related articles. In a review of 87 studies on community gardens, Guitart et al. authors found only a single study focused on ecology (Guitart et al. 2012). This finding may be exacerbated by the review’s focus on community gardens rather than UA more broadly, yet socio-ecological systems research in general is undeniably skewed in favor of the social sciences (Epstein et al. 2013). The ecological work that has been conducted since Guitart’s review focuses primarily on cataloguing and comparing the biodiversity of UA to peri-urban agriculture (UPA) and rural sites (Ricketts and Imhoff 2003, Goddard et al. 2010, Beninde et al. 2015, Lin et al. 2015, Speak et al. 2015). These studies have demonstrated that an impressive array of species inhabit urban gardens, but cohesive theories to explain the mechanism behind this and divergent trends is less developed (Egerer, Li. et al. 2018). At the same time, there is a pressing need for ecological research in UA to forge closer integration with social science research on the topic, in short, to create an urban agroecology discipline. To encourage advances on these fronts, this chapter overviews some ecological concepts and theories applicable to UA, as well as the overall characteristics of UA itself.

Understanding the Ecosystem - What is Urban Agriculture?

Designing an ecological study of UA necessarily begins with its definition (Mougeot 2010, Zezza and Tasciotti 2010. Orsini et al. 2013, Lin et al. 2017). Agriculture implies some form of food production, yet most UA sites are composed of food, ornamental and weed species (Mougeot 1999. WinklerPrins 2002, Guitart et al. 2012. Lin et al. 2017). Indeed, many ornamentals are planted as companions to food crops, providing benefits including pollination and pest control services (Baker 1989. WinklerPrins 2002, Colding et al. 2006. Lin et al. 2015). Focusing purely on food production would ignore these synergies and obscure many of UA’s unique characteristics, including its high levels of planned and associated biodiversity (Daniels and Kirkpatrick 2006a, 2006b. Goddard et al. 2010. Lin et al. 2015, Speak et al. 2015). Yet, UA comes in many different sizes and forms, from large-scale community gardens, rooftop gardens on top of businesses and restaurants, indoor hydroponics operations, edible city trees and landscapes, potted apartment windowsill plants to guerrilla gardens hiding in city sidewalks or on display in vacant lots (Mougeot 1999. Zezza and Tasciotti 2010, Lin et al. 2017).

In order to provide an appropriate context for study and comparison, ecological studies of UA should define and possibly limit what type of UA they are considering. Some sites may be more appropriate than others, depending on the questions and organisms of interest. For example, larger UA plots including community gardens or urban farms may provide the spatial scale necessary for sampling larger or more mobile organisms such as mammals, lizards and birds (Preston 1962, Bowman et al. 2002). In contrast, rooftop gardens may provide better insight on the effects of novel soil infrastructure and nutrient flows in cities (Buehler and Junge 2016, Pennisi et al. 2016. Harada et al. 2018. Harada et al. 2018, Harada et al. 2019). Potted plants and w indowsills can elucidate impacts of space and light, while guerrilla gardens can be particularly useful for studying temporally-dependent dynamics (Orwell et al. 2006, Adams and

Hardman 2013). Comprehensive understanding of UA as an ecosystem necessarily encompasses all of these forms. However, including all types of UA in a single study makes replication, without confounding effects, difficult to achieve, particularly at the scale of a city (Goddard et al. 2010. Egerer, Li, et al. 2018). Thus, the choice of which kind(s) of sites to utilize and at what spatial and temporal scales will depend on the questions at hand.

Conceptually, progress in ecological studies of UA is impeded by inconsistent definitions not only of ‘agriculture’, but also of ‘urban’. Human population density and the percentage of impervious surface are often used to categorize cities. But there is no widely agreed-upon threshold of either population density or impervious surface cover that qualifies as ‘urban’. This is due in part to differences in patterns of urban development and settlement in different places. But the lack of consistency makes it difficult to generalize across studies, and is likely one reason for the frequently conflicting narratives about the effect of urbanization on ecosystems and communities (Raciti et al. 2012). Researchers should make explicit how they define ‘urban’, and perhaps provide a justification for their definition, in order to facilitate comparison across studies.

Reviewing Ecological Concepts - What Kinds of Questions to Ask

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