We conclude by integrating these ideas into a possible scenario of rhizobiome assembly

Furthermore, UA policy in the U.S. remains largely agnostic about the sustainability of production practices and their impact on the environment. While U.S. agriculture policy narrowly focuses on the production, distribution and marketing potential of UA, broader discussion of its activities and goals proliferate among food systems scholars from a range of fields including geography, urban planning, sociology, nutrition, and environmental studies. These scholars are quick to point out that UA is much more than production and marketing of food in the city, and includes important justice elements . In the Bay Area context, we continue to see the result of this dichotomy: thriving urban farms lose their leases , struggle to maintain profitability or even viability and encounter difficulties creating monetary value out of their social enterprises. In light of the ongoing challenge to secure longevity of UA in the United States, there is a need for an alternative framework through which food and farming justice advocates can better understand and articulate what UA is, and why it matters in cities.Agroecology is defined as “the application of ecological principles to the study, design and management of agroecosystems that are both productive and natural resource conserving, culturally sensitive, socially just and economically viable” ,vertical gardening in greenhouse and presents itself as a viable alternative to productivist forms of agriculture.

Agroecology in its most expansive form coalesces the social, ecological, and political elements of growing food in a manner that directly confronts the dominant industrial food system paradigm, and explicitly seeks to “transform food and agriculture systems, addressing the root causes of problems in an integrated way and providing holistic and long term solutions” . It is simultaneously a set of ecological farming practices and a method of inquiry, and, recently, a framework for urban policymaking ; “a practice, a science and a social movement” . Agroecology has strong historical ties to the international peasant rights movement La Via Campesina’s food sovereignty concept, and a rural livelihoods approach to agriculture where knowledge is created through non hegemonic forms of information exchange, i.e. farmer to farmer networks . Mendez et al. describe the vast diversity of agroecological perspectives in the literature as “agroecologies” and encourage future work that is characterized by a transdisciplinary, participatory and action oriented approach. In 2015, a global gathering of social movements convened at the International Forum of Agroecology in Selengue, Mali to define a common, grassroots vision for the concept, building on earlier gatherings in 2006 and 2007 to define food sovereignty and agrarian reform. The declaration represents the views of small scale food producers, landless rural workers, indigenous peoples and urban communities alike, affirming that “Agroecology is not a mere set of technologies or production practices” and that “Agroecology is political; it requires us to challenge and transform structures of power in society” .

The declaration goes on to outline the bottom up strategies being employed to build, defend and strengthen agroecology, including policies such as democratized planning processes, knowledge sharing, recognizing the central role of women, building local economies and alliances, protecting biodiversity and genetic resources, tackling and adapting to climate change, and fighting corporate cooptation of agroecology. Recently, scholars have begun exploring agroecology in the urban context. In 2017, scholars from around the world collaborated on an issue of the Urban Agriculture magazine titled “Urban Agroecology,” conceptualizing the field both in theory and through practical examples of city initiatives, urban policies, citizen activism, and social movements. In this compendium, Van Dyck et al. describe urban agroecology as “a stepping stone to collectively think and act upon food system knowledge production, access to healthy and culturally appropriate food, decent living conditions for food producers and the cultivation of living soils and biodiversity, all at once.” Drawing from examples across Europe, Africa, Latin America and Asia and the United States, the editors observe that urban agroecology “is a practice which  while it could be similar to many ‘urban agricultural’ initiatives born out of the desire to re build community ties and sustainable food systems, has gone a step further: it has clearly positioned itself in ecological, social and political terms.” . Urban agroecology takes into account urban governance as a transformative process and follows from the re emergence of food on the urban policy agenda in the past 5 -10 years.

However, it requires further conceptual development. Some common approaches in rural agroecology do not necessarily align with urban settings, where regenerative soil processes may require attention to industrial contamination. In other cases, the urban context provides “specific knowledge, resources and capacities which may be lacking in rural settings such as shorter direct marketing channels, greater possibility for producer consumer relations, participatory approaches in labour mobilisation and certification, and initiatives in the area of solidarity economy” . Focusing on the social and political dimensions of agroecology, Altieri and others have explicitly applied the term “agroecology” to the urban context, calling for the union of urban and rural agrarian food justice and sovereignty struggles . Dehaene et al. speak directly to the revolutionary potential of an agroecological urban food system,greenhouse vertical farming building towards an “emancipatory society” with strong community health and justice outcomes. Our research builds upon this emergent body of work that employs urban agroecology as an entry point into broader policy discussions that can enable transitions to more sustainable and equitable city and regional food systems in the U.S. . This transition in UAE policymaking is already well underway in many European cities . As noted, there are many dimensions of agroecology and ways in which it is conceptualized and applied. We employ the 10 elements of agroecology recently developed by the UN FAO in our discussion of urban agroecology. These 10 elements characterize the key constituents of agroecology including the social, ecological, cultural, and political elements. Despite the emancipatory goals of agroecology, a recent review of the literature by Palomo Campesino et al. found that few papers mention the non ecological elements of agroecology and fewer than 1/3 of the papers directly considered more than 3 of the 10 FAO defined elements. In an effort to help guide the transition to more just and sustainable food and agricultural systems in cities across the U.S., we propose that food system scholars and activists consider using the 10 elements as an analytical tool to both operationalize agroecology, and to systematically assess and communicate not only the ecological, but also the social, cultural and political values of urban agroecology. “By identifying important properties of agroecological systems and approaches, as well as key considerations in developing an enabling environment for agroecology, the 10 Elements [can be] a guide for policymakers, practitioners and stakeholders in planning, managing and evaluating agroecological transitions. In San Francisco’s East Bay region, urban food production proliferates in schoolyards, in half acre lots converted to urban farms, on rooftops, and in backyards reflecting a diversity of participants, goals, impacts and challenges . The San Francisco East Bay region is also experiencing rapid gentrification and a worsening affordable housing crisis coupled with high rates of income inequality and food insecurity. The challenge of urban soil contamination creates trade offs for aspiring growers between vacant lot availability and siting on the most heavily polluted plots . Specific city policies vary in the degree to which they support or discourage urban agricultural activities, and availability of arable land across the East Bay is uneven. Our case study focuses on urban farmers in the East Bay spanning over 28 miles from El Sobrante in the northeastern edge of the bay, to Hayward in the southern East Bay as shown in Figure 1.

We include both for profit and non profit farms ranging from educational school gardens to roof top farms marketing microgreens. We employed a participatory and collaborative mixed methods approach, involving diverse stakeholders from the East Bay Agroecosystem. We held two stakeholder input sessions involving over 40 urban farmers and food advocates to co create the research questions, advise on the data collection process, interpret the results, and prioritize workshop topics for the community. We administered an online Qualtrics survey to 120 urban farms in the East Bay that had been previously identified by the University of California Cooperative Extension Urban Agriculture working group and additional outreach. The survey launched in Summer 2018, which is a particularly busy time for farmers, and in response to farmer feedback was kept open until November 2018. 35 farmers responded in total, representing a 30% response rate. While there are limitations in our ability to generalize findings to the East Bay urban farming landscape as a whole due to the relatively small sample size, we obtained a fairly representative sample of the diversity of farm types in the East Bay based on our typology of the original 120 farm types . Survey questions fell into nine categories: 1) Background Info, 2) Farm Description, 3) Operating Expenses and Revenues, 4) Land Access and Tenure, 5) Production and Soil Health, 6) Distribution, 7) “Waste” and Compost, 8) Food Access, and 9) Training, Communications, and Follow Up. There were a few open ended questions allowing farmers to express what they saw as the three largest challenges facing urban agriculture operations in the area, and policy relevant suggestions for securing spaces for urban farms and increasing community food security. In addition, we interviewed five urban farmers to deepen our understanding of the social, political, economic, and ecological constraints under which their farms operate. These farmers are particularly involved in networking efforts to strengthen urban farm viability in the East Bay. Four out of five represent locally prominent non profit farms and one subject represents an alternative cooperatively run urban farm; three interview subjects are women and two are men. Our study complied with UC Berkeley’s Institutional Review Board protocol for the protection of human subjects and all participants gave consent for participation.Farmers in our study stressed the importance of producing non food related values on their farms, including education and community building. One farmer in particular emphasized their organization’s mission of growing urban farmers growing food,” or teaching other people how to grow a portion of their food basket, thus unlocking food sovereignty and food literacy while increasing healthy food access. Another respondent reported that their farm is “highly desirable for adults with special needs that need a safe place to be outside,” echoing respondents who point out the intimate connection between food and health. Farms frequently reported hosting educational and community building workshops, cooking and food processing demonstrations, harvest festivals, and other open to the public community events enhancing the resilience and connectivity of people, communities and ecosystems. Social networks emerged as an important theme for enabling the establishment of urban farms , and sustaining operations through social connections between urban farmers and other food justice and health advocates. Farmers identified three primary challenges: revenue, land, and labor inputs. Half of all respondents reported farm earnings of $1,500 annually or less, and all four operations receiving over $250,000 in annual revenue are well funded non profit operations . Regardless of for profit or non profit status, most farms reported multiple sources of revenue as important to their continued operation , with an average of 3 revenue streams per farm. All non profit farms reported multiple revenue streams except for three, who were sustained entirely by either board donations, membership fees , and grants. The most important revenue sources for non profits include grants, grassroots fundraising, and unsolicited donations rather than sales. In addition to these monetary sources, all farms reported receiving substantial non monetary support , which adds to the precarity of operations when these informal support channels disappear.The cost of labor, and relatedly, access to capital and grant funding to pay living wage salaries, were also extremely significant challenges identified by survey respondents. The majority of respondents stated that most of their labor is volunteer rather than paid, with nonprofit respondents reporting this more frequently than for profit enterprises . The maximum number of paid staff at any operation is 20 , while the average is 4. Many farms reported the desire to be able to hire and pay workers more, but not having sufficient revenue to accomplish that goal. Annual volunteer labor participants on farms ranged from 0 to 1542 with an average of 97 volunteers, representing a significant public interest in participating in local food production. Not surprisingly, amount of paid labor and total farm income are positively correlated .