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Gwynne Mhuireach

Student in Landscape Architecture, University of Oregon

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Does urban “green” harbor healthier microbes?

We evolved in natural environments, characterized mainly by soil, water, vegetation, and the innumerable microorganisms associated with each. Many researchers have observed linkages between human well-being and exposure to green space, including mental restoration, reductions in disease and mortality, better birth outcomes, and decreased crime and violence. Explanations for why these benefits are observed are often based on the idea that humans are evolutionarily predisposed to prefer environmental settings that confer survival advantages, namely landscapes that are similar to the savannas and woodlands that humans are thought to have inhabited for thousands of years. Is it possible that vegetation is a source of the microbes we have co-evolved with over the millennium and whose presence we may require for physical and psychological health?

Westernized societies are plagued with increasing rates of auto-immune disorders. A recent study in New York City has shown that kids in neighborhoods with more street trees are less likely to have asthma, after controlling for socioeconomic factors. Several other research studies have found that children exposed to higher environmental diversity (i.e. living on a farm or forested rural setting versus living in a city) were exposed to higher microbial diversity and had lower rates of asthma and allergic disposition.

If we could quantify the relationships among human health, microbial diversity and urban green space, would it change the way we design cities? Should we put a higher priority on providing adequate green space for all urban residents? Majora Carter says, “Race and class are extremely reliable indicators as to where one might find the good stuff, like parks and trees, and where one might find the bad stuff, like power plants and waste facilities.” How can planners and designers ensure that all city residents will have a positive and equitable microbial experience as they interact with the invisible urban microbiome?


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    May 24 2013: A different way to think about cities and urban planning could be through the lens of ecosystem services, both provided for and by cities. Ecosystem services are the processes and conditions through which natural ecosystems help sustain human life. They are usually divided into categories: Provisioning services (products such as food and water obtained from ecosystems), Regulating services (benefits from regulation of ecosystem processes like regulation of water and climate), Supporting services (services necessary for other ecosystem services, e.g. cycling of oxygen, water and nutrients) and Cultural services (non-material benefits obtained through ecosystems). If urban planners begin to focus on cities in such a context, that could help cities become more sustainable and improve the quality of life for people in the cities.
    An example is water cycling. Water is vital for life on Earth but climate change is predicted to change precipitation cycles, likely requiring communities to plan for floods and droughts. More impermeable surfaces mean that water can’t naturally go into soil, where it can become purified, potentially leaving more water with a higher concentration of pollutants. Urban green (parks, trees, green roofs) would allow for more water to enter soil, purify itself, and re-enter the water cycle. Also, soil biodiversity and quality are linked to water regulation and purification. Planning cities to allow for the cycling of water could increase people's quality of life, and provide for the soil and biodiversity surrounding the city, which would help the growth of plants and other crops used for human consumption. I think seeing cities as one, important part of a much larger ecosystem will be necessary in the future city planning to make cities sustainable in the face of climate change and population growth.
    Jannson 2013 Ecological Economics 86:285-291 http://www.sciencedirect.com.libproxy.uoregon.edu/science/article/pii/S0921800912002388
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      May 24 2013: Great idea, Christine. I think there has been interest in urban ecosystem services for quite a while; see, for example:

      Bolund, Per, and Sven Hunhammar. "Ecosystem services in urban areas." Ecological economics 29.2 (1999): 293-301. [http://www.sciencedirect.com/science/article/pii/S0921800999000130]

      Oberndorfer, Erica, et al. "Green roofs as urban ecosystems: ecological structures, functions, and services." Bioscience 57.10 (2007): 823-833. [http://www.jstor.org/stable/10.1641/B571005]

      Tratalos, Jamie, et al. "Urban form, biodiversity potential and ecosystem services." Landscape and urban planning 83.4 (2007): 308-317. [http://www.sciencedirect.com/science/article/pii/S0169204607001375]

      If microbial community diversity were confirmed to have a human health benefit, it would be interesting to suggest that maintenance of that diversity through urban green space is also an ecosystem service.
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      May 24 2013: I agree that looking at the ecosystems services provided by green spaces is an excellent idea, and I think many cities are starting to implement this change. In regards to water filtration, I have noticed throughout Portland, many parking lots, for example the Fred Meyers on Hawthorne, have been reconstructed to include bioretention cells (depressed areas covered by vegetation to allow for filtration and infiltration), and the EPA has a page dedicated to better storm water management that include green roofs, the elimination of curbs, and permeable pavement, all of which could be beneficial to alleviate some precipitation stresses due to climate change.

      I particularly liked Christine's comment about considering cities a part of a larger ecosystem, and while looking at the benefits ecosystem services provide us, adding green spaces allows us to provide services to many of the species that are currently being threatened by our urban sprawl. With the current declines in biodiversity we are facing worldwide it is important to try to alleviate this as much as possible when planning for future development. Green spaces if designed correctly can provide stepping stones for migratory birds, and other animal populations allowing them to persist in developed areas. The Audubon Society is currently implementing a program to provide urban oases for migratory song birds.

      Green spaces can be our ecosystem service!

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