1. Introduction
Urbanization can bring important societal advancements, but rapid and unplanned expansion, especially in the developing world, can exacerbate poverty, social upheaval due to issues of displacement, water scarcity, and food insecurity (World Economic Forum 2018). It is estimated that by 2050 approximately 66% of the world’s population will live in cities, and 95% of new urban dwellers will reside in developing countries (United Nations Department of Economic and Social Affairs 2014). It is, thus, imperative to develop frameworks that can thoroughly assess the role of social alleviation and land management strategies to address urban issues, and these frameworks need to accurately capture the systems complexity that characterizes urban spaces.
One alternative approach for exploring urban socioecological systems1 could be the integration of the ecosystem services (ES) and the livelihoods frameworks in a synthesis study2 (Fig. 1). ES are benefits people obtain from nature, including material goods like water and food and nonmaterial goods like aesthetic appreciation and a sense of place (Millennium Ecosystem Assessment 2005). Livelihoods refer to “the capabilities, assets (including both material and social resources) and activities required for a means of living” (Chambers and Conway 1992). ES and livelihoods are interrelated: ES contribute toward people’s livelihoods, freedom of choice and well-being (Costanza et al. 2017; Millennium Ecosystem Assessment 2005); and strategies applied to improve local livelihoods may impact the production or provisioning of ES (Folke et al. 2005; Landreth and Saito 2014). Irrespective of this relationship, the frameworks behind each concept are commonly applied separately in natural and social sciences. The ES framework is used to look at the role of ecosystems in sustaining and fulfilling human life (Daily 2013), and the livelihoods approach is used to examine well-being in terms of humanistic and societal advancements beyond economic aspects (Lienert and Burger 2015).
ES–livelihoods framework: A visual representation of our conceptual approach. UA is a commonly employed alleviation strategy.
Citation: Earth Interactions 27, 1; 10.1175/EI-D-22-0010.1
In today’s era of rapid urbanization throughout the developing world, urban agriculture (UA) demonstrates potential to promote sustainability3 and enhance resilience4 in socioecological systems. Because of this, UA is often applied as a social alleviation and land management strategy. UA and its multifaceted5 role in the city have been commonly adopted to aid in the management of urban environments and alleviation of urban problems (FAO 1988). As defined by the United Nations’ Food and Agriculture Organization (Thomas 2014), UA is the “growing of plants and the raising of animals within and around cities.” The benefits of UA are widespread and have been shown to contribute toward enhancing local economies (Bryld 2003), food security (Zezza and Tasciotti 2010), water and habitat quality (Barthel and Isendahl 2013), food and ecological literacy (Colasanti et al. 2012), and community engagement in diverse urban settings throughout the world (Dubbeling and DeZeeuw 2011). For example, in Mexico City (MC), Mexico, the local government has recognized the important role that agriculture plays in culture and finance, while also documenting its role in addressing land degradation as a consequence of urbanization (Comisión Nacional para el Conocimiento y Uso de la Biodeversidad/Secretaría del Medio Ambiente del Distrito Federal 2016; Gobierno del Distrito Federal 2014; Thomas 2014). For this reason, the MC government promotes agriculture as a livelihood practice and land management strategy, not only in its most traditional forms (including its characteristic chinampas or floating gardens—more on this in study area description) in the periurban6 fringe of the city but also as small-scale practices adopted by individual households and communities in MC (Thomas 2014).
The ability of UA to simultaneously provide numerous social, economic, and ecological benefits beyond the provision of commodities7 (Lovell 2010) places it as a multifunctional8 poverty alleviation and land management strategy (Abler 2004; WinklerPrins 2017). UA transforms open lots, rooftops, and other urban land uses into urban spaces that meet local needs by providing a supplemental source of income and nonmaterial social benefits while supporting a food and ecologically productive environment (Lin et al. 2015; Lovell 2010). Yet, existing scientific assessments of the multifunctionality that characterizes UA are criticized for relying on “reductionist” and “narrow economic and policy-based approaches” that limit the depth of analysis and comprehension of agricultural systems (Wilson 2007). This is likely because the approaches used favor environmental over social theory or the opposite, not considering both equally. To address these shortcomings, scholars advocate for holistic, interdisciplinary, and integrative metalevel (object focused) frameworks that better encompass the range of potential outcomes, over both society and nature, by UA (Renting et al. 2009).
Applying ES–livelihood hybrid methods when studying urban socioecological systems can provide insights of existing feedback mechanisms (Fig. 1) (Kaltenborn et al. 2017). Yet few studies apply ES and livelihood methods in a manner that places them as complementary perspectives (Landreth and Saito 2014; Wakuru 2013). In the UA context, the ES framework generally focuses on UA’s immediate socioenvironmental impacts (e.g., access to fresh produce, education) and overlooks further effects over communities (e.g., alleviation of malnourishment, reconnection to agricultural heritage and a well-integrated local community) (Landreth and Saito 2014). Meanwhile, the livelihoods approach, which tackles community impacts, can overlook evaluating the environmental impacts of commonly adopted mitigation strategies (Landreth and Saito 2014). However, when looking at the impact of UA as a livelihood alleviation strategy over ES in a developing world setting, Landreth and Saito (2014) were able to document the need for more ecosystem-compatible practices that benefit residents without being detrimental to the environment. Similarly, when discussing the impacts of poor ES provisioning over livelihoods, Wakuru (2013) was able to relate farmer unawareness over health risks linked to irrigating crops with polluted water back to a lack of support from urban planners in training urban farmers and implementing strict UA regulations. Despite the value of these assessments, interdisciplinary and integrative approaches are not the norm when studying complex areas of inquiry like urban socioecological systems (Grimm et al. 2013). Moreover, most outputs from ES and livelihood studies remain scattered across their home disciplines (Guitart et al. 2012; Landreth and Saito 2014; Wakuru 2013).
A comprehensive integration of the ES and livelihood approaches could provide a venue that captures the complexity behind urban socioecological systems while examining the relationship of UA with ecosystems and human well-being. That is why our study design integrates these two well-established social and ecological scientific perspectives, that is, the livelihood and ES approaches, to provide a thorough analysis of UA’s multifaceted role in MC. MC is a fast-growing Latin American city lends itself useful for this type of examination due to its abundance of urban and periurban agriculture, which are at advanced and nascent stages of development (Thomas 2014; United Nations Department of Economic and Social Affairs 2014). Although this study is an innovative coupling of the livelihoods and ES approaches, it also provides an applied synthesis for UA in the context of MC. As such, we addressed the following questions: What are UA’s contributions to ESs and livelihoods in MC? Are there any unintended outcomes? Overall, we expected to record various contributions of UA to MC, ranging from enhanced social well-being to the provisioning of a diversity of ES. We also expected to identify some negative contributions associated with UA that may go unnoticed without an interdisciplinary lens. Further, the integrative approach positioned in this manuscript attempts to distinguish itself from traditional approaches that either focus on the impacts of livelihoods and associated strategies (used to increase local capitals9) over ES provisioning, or on the role of ES in increasing well-being and local livelihoods by providing a complementary coupling of both frameworks.
2. Materials and methods
a. Study area
This study focused on applying our ES–livelihood integrative approach to study UA in MC, the capital of Mexico (Fig. 1). MC is the most populated city in Mexico (as of 2015, 8.9 million people) and has a high level of population density (66 people km−2 of land area) (World Bank Group 2021). We selected MC because it offered a diversity of distinct social and environmental features like urban community gardens, terraced nopal (cactus) production, heritage farming, and a rapidly urbanizing metropolitan area. MC is home to well-documented agricultural practices that are transitioning from principally noncultivated periurban areas into areas that are now fully incorporated into UA (FAO 2014). Prior to colonial times, MC was known as Tenochtitlan, and it was the capital of the Aztec Empire. The city is located in the Valley of Mexico and formerly was surrounded by inland freshwater lakes. The surrounding lakes and wetlands made possible an intricate system of human-made islands that supported a highly productive and sustainable form of agriculture, termed chinampas (Rojas 1995; Jiménez et al. 2020; González-Pozo 2016). During colonial times the lakes were drained and most of the chinampa (small farms built on wetlands) production was halted but the cultural heritage of agriculture remains as the chinampas were able to make one of the great early human civilizations nearly self-sufficient in terms of food production and sustainable water management (Ezcurra 1990; Jiménez et al. 2020). Today the chinampas (“floating” farms located in the lake basin) are most commonly found in the large-scale agricultural areas of southern MC (shown in green in Fig. 2). Crucially, they are recognized by MC’s government, along with other larger-scale agriculture in the area, as legitimate means to addressing land degradation consequence of urbanization (Thomas 2014) and providing numerous ES (including biodiversity, carbon storage, runoff retention and erosion control—see Comisión Nacional para el Conocimiento y Uso de la Biodeversidad/Secretaría del Medio Ambiente del Distrito Federal 2016).
MC and simplified delimitations of its urbanization levels (blue ovals), as delineated in Dieleman (2017). (Note: Dieleman’s urbanization levels are provided as a frame of reference but not used as measures of analysis in this study. The ovals are simplified delineations and not formal boundaries.) (b) The map includes population density (white-to-red gradient represents low-to-high density), major watersheds (dotted outline), distribution of conservation land (blue) and of large-scale agriculture (green), and an outline of the city’s urban core (gray outline). (a) An inset map is provided to show the location of Mexico City in Mexico.
Citation: Earth Interactions 27, 1; 10.1175/EI-D-22-0010.1
b. Mapping urban agriculture
UA maps are frequently based on institutional or voluntary reporting of UA projects (Taylor and Lovell 2012). To map UA in MC, we adopted methods from Taylor and Lovell (2012) (Fig. 3), and obtained 105 sites total, which were reduced to 73 after filtering duplicates, misclassifications (e.g., a health care store mistakenly classified as a UA site) and initiatives that no longer existed (Figs. A1a,b; see the appendix). Of these 73, we were able to confirm 45 with satellite imagery (Google 2019) and used Esri’s (2018) ArcGIS Pro to outline and calculate their extent (Fig. A1c), creating the first published georeferenced dataset of UA projects in MC (to our knowledge) that included information regarding the UA project’s name, mission, garden type, produce grown, address, coordinates, and URL to its online listing. Since these methods only accounted for small-scale UA, and MC has a long history of agriculture distinguished by its chinampas throughout periurban zones (Fig. 2), we identified larger-scale and commercial agriculture through 30-m land-cover data (Commission for Environmental Cooperation 2020). We recognize that the spatial scales of assessment for small-scale UA and large-scale agriculture in MC are broadly different; however, we choose to maintain both units of analyses to provide a wide picture of the various ways in which agriculture takes place in MC and the different contributions linked to each type (which may have different types of significance regardless of size). We also avoid making immediate comparisons of sites across scales and merely bring attention to finer findings when diving into small-scale UA-specific observations.
Mapping urban agriculture (adapted from Taylor and Lovell 2012) and estimating food production. We compiled locations until saturation, i.e., once no additional sites or UA projects appeared, through online searches of relevant keywords in Spanish and English (e.g., “urban agriculture,” “food gardens,” “community gardens” AND “Mexico City). We obtained 73 individual sites in total, which were available in various formats like online and academic articles, webpages, georeferenced spatial data layers, etc. that listed UA sites reported by non-profit, academic, governmental institutions, and individuals. Methods for our food production estimates (performed by UA type categories specified in Table 2) are also shown.
Citation: Earth Interactions 27, 1; 10.1175/EI-D-22-0010.1
c. Analysis of UA based on ES–livelihoods framework
We identified key components, in terms of foundational assets and direct and indirect outcomes, that are associated with the application of the ES (including all four recognized categories, that is, cultural or nonmaterial, provisioning or material, supporting, and regulating; see Millennium Ecosystem Assessment 2005) and livelihoods frameworks in the study of socioecological systems. These served as guiding points for our methodological design and to evaluate material and nonmaterial improvements, diminishments, and outcomes from UA in MC. For this assessment, we performed both a qualitative and quantitative characterization and describe it in detail below along with listing our key components assessed.
1) Qualitative assessment
The first component of our integrative assessment was to evaluate the core elements of ES and livelihoods. We identified that a site’s stocks of important assets provide foundation to a community’s livelihoods (Bebbington 1999; Millennium Ecosystem Assessment 2005; Scoones 2015; Speranza et al. 2014). These stocks occur in the form of capitals: cultural, social, human, physical, financial, and natural; the latter of which further enhances ES provisioning through biodiversity, ecosystem functions and other landscape conditions (Haines-Young and Potschin 2010). Thus, we chose to focus on the evaluation of the six forms of capitals, paying special attention to plant species (or crop) biodiversity.
Given our UA context, we evaluated crop diversity and associated vegetation using various online resources including the web sites and social media outlets of our 73 UA sites. We also assessed diversity of edible plant species throughout the city (not just for the UA sites), by identifying and mapping the distribution of the first 50 search results for self-reported plant species in MC from naturalista.mx (California Academy of Sciences and National Geographic Society 2021), a citizen science online platform. Historical documents and other evidence of UA in MC were reviewed from peer-reviewed literature and published reports to render the value or role that the presence of these specific crops may represent for MC residents (socially and ecologically).
For livelihoods, the six forms of capitals contribute toward people’s means of living; we performed an extensive review of secondary data and existing literature to yield specific examples of UA’s relation to each of the following capitals: social, cultural, human, financial, physical, and natural. An exhaustive search of peer-reviewed literature, government reports, and nongovernmental/intergovernmental reports, was conducted to identify the ways in which UA contributes toward capitals in MC. Compiled literature is cited alongside our articulation of UA link to each of the livelihood capitals (Table 3). The criteria for inclusion in the analysis was for the source to provide reasoned evidence based on empirical observations that focused on an area that included MC. Selection for a specific contribution to capital was then classified as a positive, negative, or mixed contribution to livelihoods in MC. The search was conducted until the classifications of contributions reached the point of analytical saturation (Glaser et al. 1968). The review was not all encompassing but limited toward the scope of UA’s role in MC.
Furthermore, we used the official description of each UA site (mapped following the methods described in the previous section), including its mission and vision when available, to determine what cultural ecosystem services (CES) were provided. Here, we refer to CES as benefits obtained from experiencing nature directly (Millennium Ecosystem Assessment 2005). To code for references of these CES, we created an a priori list of 10 CES codes using Millennium Ecosystem Assessment (2003) typology: aesthetics, cultural diversity, cultural heritage, education, inspiration, knowledge systems, recreation and ecotourism, sense of place, social relations, and spirituality. Furthermore, we coded the descriptions of UA sites for references to ecosystems services they potentially provide (not actually, as evidence documenting actual provisioning was not widely available for all sites). Therefore, if in its description a UA site mentioned they offered gardening workshops, we coded this reference as “education” CES. Other times, the description of a site contained a theme verbatim; for example, “facilitate…community processes by constructing spaces for growing food that foment social cohesion” (Huerto Tlateloco 2020) was coded as “social relations.” In the discussion of results, we use language such as “these sites provided educational opportunities.” The proper phrasing should be “these UA sites mentioned in their official descriptions that they provided education opportunities which we coded as ‘education.’” However, for brevity, we will use the former phrasing when discussing our findings.
We found official mission and vision statements for 45 out of 73 sites (60%), usually in their respective Facebook pages, and entered and qualitatively analyzed them using NVivo v.12 software. Since the information was in Spanish, one coauthor fluent in Spanish compiled and coded the data and also consulted translations with two coauthors who are native Spanish speakers. Last, we followed an iterative coding process throughout our assessment so we could code for emerging themes (Saldaña 2016). This opened up our approach to recording evidence of other ES forms (including provisioning of raw material goods, such as food and medicine, or other ES types like regulating) present throughout the various UA sites and that were being analyzed in our quantitative assessment as well.
2) Quantitative assessment
We quantified food production, which is a type of provisioning or raw material good ES, derived from agriculture throughout MC (small-scale UA and large-scale or commercial periurban agriculture). We utilized site-reported values on annual food production (kg) when available. Otherwise, an annual production equation from Clinton et al. (2018) was used to estimate this value (Fig. 3). This equation incorporates Food and Agriculture Organization Corporate Statistical Database’s values (FAO Statistics Division 2019) and accounts for the variety of produce grown (also obtained from site reports, when available, and is included in the attribute table of the developed UA database).
We used the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) tool (3.5.0), a land-cover based mapping software used to depict ecological functioning associated with ES provisioning, (Sharp et al. 2018) and data on biological and physical landscape conditions for urban areas (as in Rodríguez González et al. 2022) to map indicators of supporting and regulating ES. Supporting and regulating ES are two categories of ES that help regulate and support local ecosystems (Millennium Ecosystem Assessment 2005). Using InVEST, we mapped habitat availability and pollination potential to analyze supporting ES; carbon storage and evaporative cooling from heat loss (InVEST in combination with a Bonan 2015 equation) to represent climatic regulating services; and nutrient (nitrogen and phosphorus) and stormwater retention as indicators of hydrologic regulating ES. We used a 30-m resolution national land-cover dataset (Commission for Environmental Cooperation 2020) clipped to MC’s extent. As forms of urban greenspaces are commonly overlooked in such data layers and resolutions, we reclassified pixels known to be urban vegetated areas according to existing data (Secretaría del Medio Ambiente 2014). We used ArcGIS Pro 2.2 (Esri 2018) to prepare the data. Map outputs were used to assess the distribution of ES high-provisioning areas in relation to agricultural land in MC.
Because the relatively unfragmented vegetated land in periurban MC overshadows smaller vegetated locations at the urban core (Figs. 4, 5a), we performed a supplemental analysis for the urban core that illustrated trends of ES trade-offs relating to UA within this subarea. We looked at the relationship between the presence of food production and all other ES types by performing Spearman’s correlations among pixels within the urban core of MC (area outlined in Fig. 2 following population density and urban development) that provided multiple ecosystem services in high amounts. High-ranking sites were defined as the top 20th percentile of total pixels (or raster map product cells) per ES using the R Statistical Language (R Development Core Team 2006), and cells within the top 20th percentile (for each service) were binarized (1 being a top 20th percentile cell) and designated as a high-provisioning area (Blumstein and Thompson 2015).
Final mapping of UA in MC, smaller maps showcase small-scale UA (i.e., within the urban core) while the color green shows the distribution or large-scale agriculture.
Citation: Earth Interactions 27, 1; 10.1175/EI-D-22-0010.1
In the livelihoods context, the contribution of UA to the six forms of capitals were also quantitatively examined by using measures such as: literacy (human), income and yields (financial), networks and metrics of social cohesion (social), water conservation (physical), soil quality (natural), and quantification of spaces for social cohesion (cultural) (Hussein 2002; Scoones 2015).
3. Findings and discussion
Although agriculture is often presented as a means to producing food, our synthesis illustrated that, in MC it can serve a range of purposes beyond this, most of which also contribute to human and environmental well-being (Table 1). In this section of our manuscript, we provide an overview of the extent of agriculture in MC. Then we discuss the range of purposes that UA plays in MC, summarized under three key observations: first, that UA connects people to nature through culture and their own livelihoods, noting that poverty is still persistent among many farmers; second, that UA does contribute to city resilience but sometimes this comes with environmental trade-offs; and third, that UA may be tied to a myriad of other unintended outcomes, some of which are negative. We then dive into the limitations that comes with the interpretation of our findings due to methodological and scholarly constraints, and place our findings within the context of advancing interdisciplinary work for the evaluation of socioecological systems in general.
Overview of the relationship between agriculture and different capitals in MC. This is an exemplar of a few of the contributions of agriculture in MC and exclude findings from the ES assessment. These examples correspond to both large-scale agriculture and small-scale UA.
a. An overview: Agriculture by the numbers
In MC, agriculture extents throughout approximately 27.70% of the city’s total land area; of this, 99.79% is large-scale agriculture occurring in periurban areas of MC and generating around 510 500 000 kg of food annually. Small-scale UA or agriculture within MC’s urban core occurs as one of five types: garden lots at ground level, greenhouses, hydroponic systems, rooftop gardens, or vertical gardens (Fig. 4), and these, in totality, generate 24 742 kg of food, which is easily overshadowed by the tons of food produced by large-scale commercial agricultural land (Table 2, Fig. A3). Descriptions, mission statements, coordinates, addresses, and reported and estimated food production for all sites compiled for these calculations are provided in Table A1.
Production by agriculture (43 UA sites were food producing).
b. Agriculture as a means of connecting people and nature (and limitations in its capability of addressing poverty)
The obvious connection between agriculture and cultural capital is the acknowledgment that food plays a crucial role in the creation of Mexican cultural capital (Flora et al. 2012). The food that UA provides MC makes a substantial contribution to the cultural exercise of cuisine. Edible plant species are found throughout the city and not limited to the periurban sector (see the appendix for distribution of first 50 plant sighting results that include an edible species, as downloaded from a citizen science website). Broccoli, chard, spinach, celery, pursh seepweed, purslane, aromatic herbs, lettuce, radish, pumpkin, maize, potato, carrot, and fava bean are reported to be grown in MC (Table 3). The agricultural products that UA provides improve health outcomes by improving diets, provide fodder for livestock, enhance food security, provide saleable assets, drive employment, and form the core life source for subsistence farmers (Table 4). The contribution of the aromatic herbs to the cultural (cuisine) and medical well-being of the people is deeply rooted in Mexican history and remains a part of contemporary household practices (DuBois 2015; Losada et al. 1998; Palma-Tenango et al. 2017; Torres-Lima et al. 2000; Guzmán Fernández et al. 2020).
Main agricultural products by delegation, region, and environment in MC (translated and adapted from Comisión Nacional para el Conocimiento y Uso de la Biodeversidad/Secretaría del Medio Ambiente del Distrito Federal 2016).
UA contributions to natural capital in MC summary. Sources: Bausch (2017), Dieleman (2017), Gobierno del Distrito Federal (2014), Mancebo (2018), Schteingart and Salavar (2010), Sheinbaum Pardo (2008), Torres-Lima and Burns (2002), Aguilar (2008), Kotchen and Moore (2007), Gobierno del Distrito Federal (2013), Jiménez et al. (2020), de Martínez (2007), Mougeot (2000), Gobierno del Distrito Federal (2012), Secretaría de Desarrollo Rural y Equidad para las Comunidades (2018), Torres-Lima and Rodríguez-Sánchez (2008), Losada et al. (1998), Mougeot (1996), Rivera-Martinez (2002), Torres-Lima et al. (1994), Torres-Lima et al. (2000), Lumsden et al. (1987), Sanders et al. (1979), Johnson (2012), Canabal Cristiani (1997), Smit et al. (2001), Sanders (1976), González-Pozo (2016), Mazari-Hiriart et al. (2008), Merlín-Uribe et al. (2013), Losada et al. (1996), Telesetsky (2014), DuBois (2015), Ezcurra et al. (2006), Leon-Portilla (1992), Losada et al. (2009), Parsons (1991), Rojas (1991, 1995), Soriano (1999), Cruz Rodriguez (2001), Duhau and Giglia (2007), González-Alejo et al. (2019), Lerner et al. (2013), FAO (1988), Smit and Nasr (1992), Canabal Cristiani et al. (1992), Dubbeling and deZeeuw (2011), Filippini et al. (2019), Li (2007), Llana (2008), Thomas (2014), Palma-Tenango et al. (2017), Guzmán Fernández et al. (2020). Note: Italics indicate no examples were found.
The significance to local cuisine is not the only way in which agricultural cultivation shapes culture in MC (Table 5). The diversity of cropping systems in MC is key to contributing to cultural resilience through livelihood diversification and aiding in farmer decisions to balance agroecological concerns with social and economic benchmarks (Tables 2, 3). Moreover, these considerations play an important role in establishing cultural organizations. The UA cultural organizations are informed by multigenerational practices that shape economic, social, and physical spaces, cutting across social and spatial divides with practices like family gardens, chinampas, and upland agriculture (Table 5). The result of this is the foundation of a collective known as Campesinos, who share a cultural identity as farmers (Table 5).
UA contributions to cultural capital in MC summary. Sources: Gobierno del Distrito Federal (2014), Bausch (2017), Jiménez et al. (2020), Torres-Lima (2000), DuBois (2015), Lerner and Eakin (2011), Losada et al. (1996), Duhau and Giglia (2007), González-Alejo et al. (2019), Palma-Tenango et al. (2017), Torres-Lima et al. (1994), Losada et al. (2000), Torres-Lima and Burns (2002), Torres-Lima and Rodríguez-Sánchez (2008), Torres-Lima et al. (2018), de Martínez (2007), Losada et al. (1998), Mazari-Hiriart et al. (2008), Merlín-Uribe et al. (2013); Mougeot (2000); Altieri (1992), Jiménez-Osornio et al. (1990), Rivera-Martinez (2002), Yih and Vandermeer (1988), Merlín-Uribe (2009), Barthel and Isendahl (2013), Isendahl and Smith (2013), Leon-Portilla (1992), Ezcurra et al. (2006), Rojas (1995), Feinman (1997), Morehart and Frederick (2014), Dieleman (2017), González-Pozo (2016), Sanders (1976), Ezcurra (1990), Canabal Cristiani (1997), Soriano (1999); Guzmán Fernández et al. (2020). Note: Italics indicate no examples were found.
Beyond the traditional Campesino, and its relationship to the land, small-scale UA also supports human–environment interactions by promoting tenants of environmental conservation and stewardship10 in MC. Informal agricultural education (i.e., nondegree seeking) goes beyond agricultural workshops, classes, and demonstration gardens. One example of this is Azcapotzalco Centro Verde (2020), they offered education around “understanding and respecting nature” (Table A2). Moreover, several other UA sites used garden spaces to foment environmental education, environmental awareness, and connection to nature (Table A2). People’s knowledge of building healthy lifestyles, skills for off-farm employment, and agricultural production and sales abilities are also enhanced through the education opportunities that agriculture in general supplies (Table 6). In our qualitative coding of CES, education was mentioned most-often (83%), followed by social relations (49%), heritage (20%), recreation (6%), aesthetic (6%), and identity (3%) (Fig. 5). In this way, UA at the urban core often serves as spaces to build community and develop social relations while promoting agricultural education (informally) and heritage. Ópalo Huerto (2020), for instance, listed “community-building” as one of the garden’s values (Table A2). Numerous sites sought to preserve Indigenous farming practices and cultural heritage. Users of the Acatitlan Urban Garden (Tobon 2019), as an example, grew culturally relevant crops and painted murals with images of native culture (Table A2). The distribution of themes for CES indicated presence of other nonmaterial benefits as well, including connections to nature and contributions to mental health (Fig. 5). The latter, combined with UA as a physical activity and vegetable consumption, plays a role in decreasing rates of chronic diseases in MC (Table 6) (also refer to Secretaría de Desarrollo Rural y Equidad para las Comunidades 2018; Rivera et al. 2012; Bridle-Fitzpatrick 2015). Only 10 out of 45 small-scale UA sites (22%) did not mention CES in their mission statements at all, and among the remaining 35 sites, we found references to 6 out of 10 CES.
UA contributions to human capital in MC summary. Sources: Bausch (2017), Cruz Rodriguez (2001), Losada et al. (1998), Torres-Lima and Burns (2002), Torres-Lima et al. (1994), DuBois (2015), González-Alejo et al. (2019), Mancebo (2018), de Martínez (2007), Secretaría de Desarrollo Rural y Equidad para las Comunidades (2018), Soriano (1999), Torres-Lima et al. (2000), Torres-Lima et al. (2010), Torres-Lima and Rodríguez-Sánchez (2008), Losada et al. (2009), Bridle-Fitzpatrick (2015), Dieleman (2017), Dávila (2005), Wiggins and Holt (2000), Lumsden et al. (1987), Romero and Chías (2000), Consejo Nacional de Población (2012), Duhau and Giglia (2007), Jiménez et al. (2020), Sanders et al. (1979), Parsons (1991), Rivera-Martinez (2002), Lerner and Eakin (2011), Rivera et al. (2012), Barthel and Isendahl (2013), Ezcurra et al. (2006), Isendahl and Smith (2013), Leon-Portilla (1992), Mancebo (2016), Sanders (1976), Ellis and Sumberg (1998), McClintock (2014), Llana (2008), Telesetsky (2014), Canabal Cristiani (1997), Guzmán Fernández et al. (2020). Note: Italics indicate no examples were found.
Last, our study analysis demonstrated that agriculture, as income source, links people with nature but those links come with limitations. UA as an economic pillar in MC can be traced back to the founding of the city by the Aztecs (Barthel and Isendahl 2013; Leon-Portilla 1992; Torres-Lima et al. 1994), and, in current times, influences the social and economic factors driving domestic and international labor migration (Table 5). For many households, agriculture is the primary and/or secondary source of income (Table 7). UA improves capabilities to elevate households out of poverty by providing livelihood diversification and nonmaterial social benefits (Table 7). However, UA is unable to fully eliminate poverty on its own (Table 8). This persistent poverty can be attributed to many things, but, where UA is the sole source of income (especially true in periurban areas), it is observed that many of the assets associated with agriculture (which already are limited) are not particularly salable and flexible in their economic application. Additionally, farmers are further harmed by limited market access, constrained land productivity, and few opportunities outside of agriculture due to limited ability to build skills for more profitable off-farm employment (Bausch 2017; Dieleman 2017; de Martínez 2007; Secretaría de Desarrollo Rural y Equidad para las Comunidades 2018). Thus, households engaged in UA can be seen as having poor economic resilience and a high degree of vulnerability to economic shocks. However, where urbanization is most prevalent, UA is often used as a means to income diversification, with practitioners moving from the informal to the formal economic sector and supporting other sectors of the wider economy in the meantime (Table 7). This helps improves the economic resilience of vulnerable populations (Lyons and Snoxell 2005), especially women, who are further supported by spaces of social cohesion created to sell food, ornamental plants, and tree seedlings (Tables 7, A2). Further market engagement is promoted when the local urban market connects with that of periurban and rural areas (Table 7).
UA contributions to social capital in MC summary. Sources: Bausch (2017), Losada et al. (1998), Secretaría de Desarrollo Rural y Equidad para las Comunidades (2018), Dieleman (2017), Torres-Lima et al. (2010), Torres-Lima and Burns (2002), Eakin et al. (2019), Cockram and Feldman (1996), Torres-Lima (2000), DuBois (2015), Losada et al. (2009), de Martínez (2007), Telesetsky (2014), Torres-Lima et al. (1994), Torres-Lima et al. (2018), Torres-Lima and Rodríguez-Sánchez (2008), Firth et al. (2011), Soriano (1999), Barthel and Isendahl (2013), Isendahl and Smith (2013), Parsons (1991), Lerner and Eakin (2011), Duhau and Giglia (2007), González-Alejo et al. (2019), Merlín-Uribe (2009), Mancebo (2016, 2018). Note: Italics indicate no examples were found.
UA contributions to financial capital in MC summary. Sources: Bausch et al. (2018), Gobierno del Distrito Federal (2013), Dieleman (2017), DuBois (2015), González-Alejo et al. (2019), Instituto Nacional de Estadística Geografía e Informática (1990), Losada et al. (1998, 2009), de Martínez (2007), Rivera-Martinez (2002), Romero and Chías (2000), Torres-Lima and Burns (2002), Torres-Lima et al. (1994, 2000), Barthel and Isendahl (2013), Canabal Cristiani (1997), Llana (2008), Telesetsky (2014), Cruz Rodriguez (2001), Jiménez et al. (2020), Bausch (2017), Duhau and Giglia (2007), Johnson (2012), McClintock (2014), Merlín-Uribe (2009), Mougeot (2000), Rivera et al. (2012), Secretaría de Desarrollo Rural y Equidad para las Comunidades (2018), Smit and Nasr (1992), Torres-Lima et al. (2010), Lerner et al. (2013), FAO (1988), Rathgeber (1990), Cockram and Feldman (1996), Torres-Lima and Rodríguez-Sánchez (2008), Torres-Lima et al. (2018), Losada et al. (1996), Guzmán Fernández et al. (2020). Note: Italics indicate no examples were found.
c. Agriculture as a means to enhancing resilience, sometimes at the expense of other outcomes
Agriculture has great cultural significance because it leads to food production while helping preserve Indigenous knowledge relating to cultivation and husbandry practices (Table 5). The cultural importance placed on agriculture promotes it as a valued option when addressing city resilience goals (MC’s government formally incorporated UA into their citywide climate change adaptation policies; see Gobierno del Distrito Federal 2014). UA contributes to physical capital by helping shape the city through increasing green space (providing a green belt) and leading to infrastructure modifications (whether leading to constraints or improvements) (Table 4). The cultivation of diverse crop species (Table 3) helps with ecosystem resilience (Thomas 2014; Dieleman 2017). Specifically, periurban agriculture in MC demonstrates a large capability of enhancing ecological resilience against urbanization-caused degradation because of its contribution to natural and physical capital through improving vegetation access, biodiversity, land and growing conditions, carbon sequestration, and overall climate resilience (Tables 4, 9). Additionally, it also acts as a natural buffer for the city’s water and sanitation infrastructure (chinampas, historically were advanced ordered agricultural systems and were effective early water management systems that facilitated the very existence the Aztecs and early Mexican civilizations) (Table 9). These findings are supported by our mapping of related ecological functioning (Fig. 6a). However, agrarian livelihoods can also bestow an inherent vulnerability to pests, disease, stagnant or declining yields, and market/labor/food/income volatility.
UA contributions to physical capital in MC summary. Sources: Bausch et al. (2018), Gobierno del Distrito Federal (2012), DuBois (2015), de Martínez (2007), Secretaría de Desarrollo Rural y Equidad para las Comunidades (2018), Torres-Lima et al. (2010), Torres-Lima and Burns (2002), Torres-Lima et al. (2018), Torres-Lima and Rodríguez-Sánchez (2008), Aguilar (2008), Cruz Rodriguez (2001), Dieleman (2017), González-Alejo et al. (2019), Jiménez et al. (2020), Pensado Leglise (2001), Torres-Lima et al. (2000), Johnson (2012), Telesetsky (2014), Bausch (2017), Dávila (2005), Losada et al. (1998), Lumsden et al. (1987), Thomas (2014), Torres-Lima et al. (1994), Losada et al. (1996), Rivera-Martinez (2002), Canabal Cristiani (1997), Wiggins and Holt (2000), Consejo Nacional de Población (2012), Mougeot (1996), Donkin et al. (1999), Llana (2008), Ruel et al. (2008), Ezcurra et al. (1999), González-Pozo (2016), Barthel and Isendahl (2013), Isendahl and Smith (2013), Parsons (1991), Guzmán Fernández et al. (2020). Note: Italics indicate no examples were found.
(a) Distribution of supporting and regulating ES in MC, where periurban trends are more noticeable; and (b) Pearson’s correlations of ES provided in high amounts within the urban core (to observe trends not noticeable at city level) in relation to the distribution of food-providing (“fp” in matrix) UA sites.
Citation: Earth Interactions 27, 1; 10.1175/EI-D-22-0010.1
Although there was a positive distributional relationship between periurban agriculture and different supporting and regulating ES, this relationship does not always replicate with small-scale UA (Figs. 6a,b, A3). Despite the importance of its social-driven role (Fig. 5), small-scale UA (along with its associated impervious surfaces) occupies valuable space that could serve to plant larger vegetation types that are much better at enhancing ecological resilience. Thus, when assessing the relationship between high provisioning of supporting and regulating ES with food production in small-scale UA, there is low likelihood for high provisioning of carbon storage and habitat quality (for pollinators and species in general), which are more typically associated with larger vegetation, when an urban green space is a small-scale food-producing UA site rather than any other green space type (including those that are not UA, such as parks, vegetated streetways, etc.) (Fig. 5b). We did find, however, that there is slight potential for enhancing the provisioning of stormwater retention and evaporative cooling (Fig. 5b), which is consistent with research findings from other UA studies (Lee and Lautenbach 2016). There appears to be no relationship with nutrient retention (phosphorus and nitrogen) (Fig. 5b). Addressing some of the existing limitations of small-scale UA in achieving specific environmental outcomes might require adopting more climate-resilient urban-farming practices. However, there is an abundance of evidence that UA practitioners and farmers lack detailed knowledge of agricultural production and sustainable cultivation (DuBois 2015; de Martínez 2007; Rivera-Martinez 2002; Secretaría de Desarrollo Rural y Equidad para las Comunidades 2018; Torres-Lima and Burns 2002; Torres-Lima et al. 2000) and adequate institutional support is necessary to make these accessible (Gulyas and Edmondson 2021). Yet, there is a dearth of formal training and technical assistance provided to UA farmers (Torres-Lima and Rodríguez-Sánchez 2008; Secretaría de Desarrollo Rural y Equidad para las Comunidades 2018; DuBois 2015).
d. Other unintended outcomes
Landreth and Saito (2014) exemplify the value of accounting for the other side of the coin within UA assessments, having found UA socioeconomic improvements occurring at expense of ecological outcomes. While many positive contributions exist, agriculture in MC showcases unintended outcomes, especially in relation to human and physical structures of the city (Tables 6, 9). Many of the negative contributions to physical structures of the city are due to UA constraints such as water scarcity, poor irrigation, poor formal economic structures, jumbled urban expansion, and a lack of resources for UA farmers and practitioners. As for human structures, negative contributions can generally be summarized in two categories: health and socioeconomic (Table 6).
For example, although UA contributes to long-term indicators of human health through improved caloric consumption and nutrition, it also generates demanding labor conditions (Table 6). Fertilizers and other agricultural inputs pollute freshwater sources and degrade soils (Table 4). Additionally, it is not clear how the food produced is distributed among MC’s populations. UA sites can portray a false image of food access in a community and may do little to address issues of food system isolation (Table 6). This is relevant in the discussion of topics like food deserts and constrained food environments, where marginalized populations have poor access to food retail options to adequately ensure food security.
As for socioeconomic issues, UA practitioners can experience increased vulnerability to unexpected shocks (whether environmental or other) largely due to income constraints but also as a result of land, social, or cultural alienation (Table 6). For example, even though UA serves as a bridge between rural and urban patterns of life and plays a large role in bringing people together across generational, cultural, ethnic, and socioeconomic divides (Table 6), some observers see this process of social change as disruptive to traditional Mexican society and ways of life, alienating farmers and residents (i.e., social alienation). Moreover, issues of land tenure come into focus with UA in MC as the city is increasingly urbanizing the surrounding area and bringing formerly arable farmland out of use (de Martínez 2007). This expansion changes the landscape and how people interact with the land—which means land alienation for some people (Table 7), where they are divorced from the land where they normally would interact with on a regular basis.
e. Limitations
This study sought to provide a more complete depiction of UA outcomes and account for trade-offs and nonpositive contributions. However, particular caution must be given to our ES estimates, as model specifications and equation estimates can impact accuracy of outputs. Our CES findings should also be interpreted with caution. The frequency and diversity of nonmaterial benefits we found in our data source does not mean that these UA sites only provided these services, or that other UA sites did not provide such benefits. For example, only two sites mentioned aesthetic benefits, yet previous research (Lindemann-Matthies and Brieger 2016) has documented multiple aesthetic benefits provided by UA in MC. Other data sources (including that from primary data, rather than secondary sources as in our synthesis) might reveal a larger diversity and occurrence of CES. Nonetheless, this synthesis attempts to address existing scholarly gaps in UA research, which largely struggles to systematically assess the diversity of outcomes associated to UA. One final limitation in applying this integrative approach comes with the caveat of combining disparate methodologies and datasets that may result in obscured findings due to the quantity of data and multitude of analysis types.
f. Interdisciplinary dialogue
Through this study we learned valuable lessons about the praxis of conducting a socioenvironmental synthesis study, as well as gathered important and relevant findings that shed light on the role that UA plays in MC. Perhaps the most valuable lesson we learned is the actual work of interdisciplinary research is a journey unto itself. We refer to interdisciplinary as the coming together of multiple areas of knowledge, brought into the research process by the scientists who have received training and developed a scholarly persona based on their disciplinary traditions. While the challenges of creating a novel theoretical approach to synthesis research were, at times, difficult due to disciplinary differences in frameworks, methods, and epistemologies, those challenges proved to be surmountable through continued collaborative work and engaged discourse. Without this approach, it is likely that our as sessment would have overlooked unintended outcomes that come with applying alleviation strategies, like UA, in complex systems that have both social and environmental spheres. Thus, we provided a systematic methodology based on the evaluation of key components, in terms of foundational assets and direct and indirect outcomes, of ES and livelihoods that provides a more expansive look into the outcomes associated from alleviation strategies, like UA, commonly adopted in socioecological systems. Additionally, this methodology can potentially be applied to examine other forms of agriculture and in other geographic, environmental, and social contexts due to its data-input flexibility. This could be an opportunity for cross-city or cross-agroecosystem comparison.
4. Conclusions
In this synthesis study, we addressed the need to apply interdisciplinary methods when assessing the role of strategies used for social alleviation and land management, because of their dual implications in the social and environmental spheres. Our argument was that an interdisciplinary approach was necessary to truly capture the myriad of outcomes associated with social alleviation and land management strategies applied in what essentially are highly complex urban socioecological systems. As proof of concept, we applied two well-established approaches from the social and ecological sciences (the livelihoods and ES frameworks) to depict the role of UA, a commonly employed social alleviation and land management strategy in developing cities. In our assessment of UA in MC (selected as study site due to its diverse application of UA), we characterized the role of agricultural practices for small-scale projects and large-scale commercial agriculture by analyzing livelihood capitals, crop diversity, ecological functions (that lead to ES production) and cultural ecosystem services through a variety of methods (including literature and secondary data analysis, mapping and spatial analytics, and qualitative thematic coding). Although disparate at times, inclusion of a wide variety of methodologies allowed us to discuss and place the contributions of UA in MC within its socioenvironmental context. By taking an inclusive approach, the praxis of interdisciplinary scholarly discourse, meaning having difficult conversations with colleagues about disciplinary traditions and ways of thinking, we were able to better situate our findings in the appropriate setting. We found that, for MC, some of these contributions can result in unintended negative outcomes like trade-offs between different ecological processes, constraints in promoting formal education beyond agroecological knowledge, and an inability to fully elevate families out of poverty. We believe this hints toward the need of further application of interdisciplinary syntheses, like that applied here, to evaluate other alleviation strategies widely employed in systems were human and nature are so closely related (as aspects from each sphere, social and environmental, might be overlooked). Our aim is that with this study we encourage researchers to consider broader scholarly lenses when supporting local governments and organizations in assessing the success of employed alleviation and land management strategies.
Acknowledgments.
This work was supported by the National Socio-Environmental Synthesis Center (SESYNC) under funding received from the National Science Foundation DBI-1639145.
Data availability statement.
Data are available from the authors upon request.
Footnotes
Socioecological systems are defined as a series of biophysical and social interactions that continuously impact shared resources in social and ecological areas.
A synthesis study, in this context, combines multiple sources and types of data in analysis and integrates them together using multiple theoretical frameworks.
Sustainability is defined as the ability to maintain or conserve in order to preserve balance and continuation.
Resilience is defined as the ability to withstand or overcome hardships and challenges.
To be multifaceted is to be made up of a multitude of elements.
Periurban is the urban fringe area.
A commodity is a durable product that is suitable for exchange.
To be multifunctional is to have versatile functions or multiple uses.
Assets that are transferable.
Stewardship is to care for or ensure the care for the environment.
APPENDIX
Supplemental Information
This appendix contains supplemental information indicating the location of UA sites (Fig. A1) and plant sightings (Fig. A2) considered in this study. Descriptions for UA sites (Table A1) as well as detailed findings for the qualitative coding of CES (Table A2) and all other types of ES (Fig. A3) are also included. Source links for all UA sites were added for reference (Table A3).
UA listings. UA listings were (a) geocoded and (c) confirmed (pink) through satellite imagery in Google Earth Pro (Google 2019). Unconfirmed UA sites (in white) were still used in assessment, as UA is small-scale and often found in small parcels, rooftops or within buildings, which can difficult our ability of identifying them. However, all sites were documented online, with web presence and/or proof of their existence through online articles, in a way that allowed for their use in the application of most out methodology. Large-scale commercial agriculture is shown in orange in (c) and was identified using land-cover data at a resolution of 30 m × 30 m (Commission for Environmental Cooperation 2020). (b) Food producing sites were identified for food production methods.
Citation: Earth Interactions 27, 1; 10.1175/EI-D-22-0010.1
Screenshot from Google Earth Pro (Google 2019) of the distribution of first 50 plant-sighting results that are edible species, from Mexican citizen science web page. First 50 plant-sighting results (a total of 4365 sightings) that were edible species were downloaded from the naturalista.mx website, a citizen-science platform to report sightings of species in MC. Sighting listings were then mapped using provided addresses in Google Earth Pro (Google 2019).
Citation: Earth Interactions 27, 1; 10.1175/EI-D-22-0010.1
UA in MC. UA sites with green space description, mission statements or goals, produce grown, total area (if value not provided, site did not have the information or could not be located via satellite imagery to estimate it), address, and coordinates. An asterisk indicates an estimated value. Note: Italics indicate no information or estimate.
Qualitative coding. Themes for CES are indicated. An asterisk (*) indicates that although a direct mention of CES was not made in a given site’s mission statement, related documentation (site websites in Table A3) provides supporting evidence of it. Additionally, mentions of material ES were found in some instances and are included in this table as supplemental information.
High-to-low provisioning of noncultural ES, including food production. The overbearing amounts of service production generated in periurban areas of MC overshadow ES generated by vegetation at the urban core.
Citation: Earth Interactions 27, 1; 10.1175/EI-D-22-0010.1
URL links for UA sites. Sites were identified through data search of UA keywords.
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