Urban microbiomes and urban agriculture

About half the human population now lives in urban environments. In 2008, populations of more developed nations were about 74% urban, while about 44% of residents of less developed countries lived in urban areas. It is projected that 70% of the world population will be urban by 2050, with most urban growth occurring in less developed countries. While there are many benefits to urban living but there are also challenges that arise, such as stress, crime, traffic, pollution and sanitation. As people moved from rural to urban populations in more developed countries during the 20th century, the incidence of asthma rose dramatically. At the same time, the incidence of asthma was much lower in rural communities and in less developed countries. These observations suggest that there may be some health benefits from rural living, such as exposure to microbes and allergens. For example, children with the highest levels of exposure to specific allergens and bacteria during their first year are less likely to have allergic sensitization, suggesting that exposure to high levels of certain allergens and bacteria in early life might be beneficial.

Urban agriculture has grown in popularity and has the potential to benefit human health and environmental sustainability. In addition to nutritional benefits arising from the consumption of fresh vegetables or eggs, these backyard gardens may provide some additional benefits of rural life for city dwellers. Keeping a garden or backyard chickens increases the level of backyard use and exposure to microbes associated with soil and plants, as well as chickens. At this point, we know very little about the microbial consequences of urban agriculture but this is an area of growing interest.

An interesting book chapter was recently published on “Urban Microbiomes and Urban Agriculture: What are the connections and why should we care?” Here the author argues that while much of the research on microbial assemblages in the built environment provides compelling examples of the importance of microbes, these studies provide an incomplete picture of microbial distribution and activity in urban systems. In addition to microbial assemblages within buildings, urban microbiomes  also include assemblages associated with exterior environments, such as building surfaces, roads, urban soils, the phyllosphere of plants, animal and human waste, water distribution systems, drainage systems, streams, and other aquatic habitats. These relatively unexplored environments include backyard gardens. By taking a broader view of the urban microbiome, the author promotes a greater understanding of the roles played by microbes in cities and connections within the urban microbiome. Although it is not open access, it is definitely worth a read.

Backyard chicken housing Davis
Backyard chicken housing in Davis, CA

2 thoughts on “Urban microbiomes and urban agriculture

  1. I am curious – do they discuss at all how they define urban? I have been wondering about this as I see more papers and studies about urban microbiomes. Is there some sort of transition we might expect as one goes from rural to suburban to urban in regard to microbiomes? And do they discuss at all if there are differences in microbiomes along such gradients?

  2. While there are some really nice studies that do look at microbiomes across such gradients, they aren’t included in this book (and may not relate to urban agriculture). This section from the preface better describes the intent of this book series:

    The two volumes of Sowing Seeds in the City were inspired by a National Academy of Science Keck Foundation (NAKFI) conference on ecosystem services (http:// http://www.keckfutures.org/conferences/ecosystem-services_podcast_home.html). Each attendee was asked to select an area of inquiry from a potential list of nine topics. At the meeting we worked in groups to come up with innovative solutions to each question. I was struck by how urban agriculture has the potential to address so many of the questions on that list. When the conference was held, urban agriculture was not on the radar. Six of those nine areas of inquiry from the NAKFI conference are shown below, along with the related sections in Sowing Seeds in the City:
    • How ecosystem services affect infectious and chronic disease: Volume 2, Section 1
    • Identify what resources can be produced renewably or recovered by developing intense technologies that can be applied on a massive scale: Volume 1, sections
    on water and waste
    • Design agricultural and aquacultural systems that provide food security while
    maintaining the full set of ecosystem services needed from landscapes and sea-
    scapes: Volume 1, all sections, and Volume 2, sections on food security
    • Design production systems for ecosystem services that improve human outcomes related to food and nutrition: Volume 1, sections on ecosystems services and
    food production, and Volume 2, sections on health and food security
    • Design a federal policy to maintain or improve natural capital and ecosystem services within the United States including measuring and documenting the effectiveness of the policy: Volume 1, sections on municipal infrastructure, and Volume 2, case studies and the sections on research, education, and
    • Develop a program that increases the American public’s appreciation of the
    basic principles of ecosystem services: Volume 2, case studies and the sections on research, education, and programming
    The scientific community is starting to recognize the potential for urban agriculture to address the issues listed above, and a social movement in urban agriculture is already well underway. To be successful, this social movement also has to be embraced by public health officials, residuals managers, municipal governments, as well as the people who actually plant the seeds. Right now, urban agriculture is many things to many people. At a minimum it provides fresh tomatoes for salads and sandwiches for urban growers during hot summer months. From a broader per- spective, urban agriculture has the potential to revolutionize our food systems, rein- tegrate both knowledge of and higher-level ecosystem services into our cities, change how our children learn, and have a broad impact on public health. The recent rebirth of urban agriculture began primarily as a social movement. With these two volumes we explore urban agriculture from a broad perspective. We hope that these books can encourage and inspire the broad range of individuals who stand to benefit from urban agriculture.

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Holly Ganz

Holly Ganz is a project scientist at UC Davis working with Jonathan Eisen on the microbiomes of built environments where animals live.