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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 22 2013: Since the trend seems to be packing more people into the city without expanding the boundaries how do we add green to the cities to improve microbial diversity? Would green roofs add enough "green" to improve diversity?
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      May 22 2013: There was a talk at at the Ecological Society of America last year on microbes and greenroofs. They were studying soil microbes in greenroofs as compared to parks and found that in general the greenroofs did not contribute significantly to the microbial diversity. There was a possibility this was due to the recent introduction of greenroofs as compared to parks. http://eco.confex.com/eco/2012/preliminaryprogram/abstract_39736.htm
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      May 22 2013: If we really are focusing on increasing the density of cities to prevent sprawl, I'm not sure if roofs alone would be enough green space (although they would certainly help!), with such a high concentration of people per area. Better placement of parks and more trees on streets could be another big contributor to making sure mroe people have ready access to green spaces and the health benefits they confer, be they microbial, psychological, or, more likely, a mix of both.
      If cities really start to get dense enough, perhaps terraced gardens/parks in high rise buildings will become more widespread; I think these are already being experimented with in Italy.
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        May 22 2013: I think this becomes a lot easier once we identify specific "helpful" microbes and which plants promote their growth.
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        May 22 2013: Why are we trying to increase densities in cities and preventing urban sprawl in the first place? I guess a better question is how? Is it that people would rather live in the city then in a rural area? Or are we as a society trying to convince more and more people this is what we should do?
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          May 22 2013: I'm not one of the most architecturally inclined, but my understand is that it's largely to increase people's proximity to things to allow more walkable cities, better public transport, and less need for cars. Also there is probably a goal of not spreading urban spaces further out than they need to be, for the sake of the environments that would be pushed out of the way.
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          May 22 2013: The global population is expected to increase by more than a third in the next 30 years. In the US they are projecting a 79% increase in developed area. The exact amount varies by region, but that is a lot of land being converted from 'natural' area to development. http://www.sciencedirect.com/science/article/pii/S016920460300197X Denser cities could reduce this impact.
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          May 22 2013: People usually want to live in cities for jobs, activities, better access to resources, etc. Living in a rural area isn't bad, but the sprawl element is an issue because of the amount of wasted resources/energy that result from urban sprawl. Not only is there the pollution issue of traveling, but in many locations where "sprawl" occurs, development has removed either critical farm land or ecosystems. The focus shouldn't just be on having people live in cities, but wherever people are living, have those cities develop in a sustainable way with their eyes towards the future and possible future population expansion. It seems many cities have been too focused on the now and not planning their cities accordingly for future population expansion.
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          May 22 2013: Yes Janielle - spot on. I don't think it's only that we're trying to increase densities in cities. It's my understanding that the rise of megacities is happening whether we like it or not.

          Laurel you might like this - from the Financial Times http://www.ft.com/intl/cms/s/2/a4c94be4-6ad6-11e2-9871-00144feab49a.html#axzz2U2riJMU3
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      May 22 2013: Oooh I love that you just brought up green roofs! Check out this TED Convo from one of my classes last year.

      http://www.ted.com/conversations/11577/if_green_roofs_were_mandatory.html
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      May 24 2013: Green roofs are a great idea and provide so many benefits from storm water management to improving the costs of the heat island effect to aesthetic value. One perhaps often overlooked benefit is the opportunity to create thousands of new jobs. If 1% of the United States' roof space in communities where the population is over 50,000 were converted to Green Roofs, it would create 190,000 new jobs. (http://www.greenroofs.org/index.php/about/greenroofbenefits)

      Here is something else to consider when thinking about Green Roofs: Many need to be planted with species that can withstand sometimes harsh environments. (UV radiation, wind, etc.) Here is an article from Scientific American explaining how these species may not be beneficial at all. http://www.scientificamerican.com/article.cfm?id=why-manhattans-green-roofs-dont-work-how-to-fix-them

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