Humans are essentially super-organisms or holobionts made up of both human cells and those of micro-organisms, such as viruses, bacteria, archea, protists, and fungi. Researchers now know the human body hosts a comprehensive ecosystem, largely established by age three, in which non-human cells vastly outnumber human cells. The latest study from the American Academy of Microbiology estimates each human ecosystem contains around 100 trillion cells of micro-organisms and just 37 trillion human cells.
But while rainforest or prairie ecosystems are now well-understood, the human ecosystem is less so. As researchers make new discoveries, there is a growing group of scientists who argue our microbiomes are deeply connected with our physical and mental health. The increased number of prebiotics and probiotics supplements on the shelf in drug stores and supermarkets, and availability of fresh pickles and kimchi in local farmers markets, are perhaps testaments to this increasingly-widespread belief.
The question at the Environmental Design Research Association (EDRA) conference in Oklahoma City was: Can we design cities to better support our microbiomes and in turn our overall health?
Richard Wener, an environmental psychologist at NYU, explained how our built environment is filled with micro-organisms. “The walls of our kitchen and bathrooms are covered in bacteria; most of them aren’t pathogenic.” The micro-organisms found in our environments are constantly interacting with our microbiomes, so we are “perpetually assembling and re-assembling different species.”
For Wener, this begs the question: “What is an individual?” If we are constantly evolving with the micro-organisms in our environment and therefore changing our composition, “what individual are we talking about?”
While our microbiomes may evolve, they still have a distinct signature. Researchers can now identify people by their unique microbiotic markers — crime-scene microbes are now analyzed in forensic studies to identify who was at a location.
Places have unique microbiotic signatures as well. Through their PathoMap project, Weil Cornell Medical College organized citizen scientists to examine the bacteria in subway stations and found there were “consistent signatures around subway stations.” The microbes in subway stations near hospitals were different from neighborhood signatures. “The microbes really depend on who lives there.” (See data visualizations of the findings).
So can we design the city in terms of microbial species? Can we design buildings and parks to create “selective pressure that supports biotic life that is good for humans?”
Turns out good microbes can be put to better use while bad ones can be suppressed.
In Brooklyn’s Gowanus Canal, a highly-polluted Super Fund site, researchers took samples of sludge at the bottom of the canal and found bacteria had been digesting some of the worst industrial waste for decades. “They co-evolved to eat solvents and toxins.” At a slow pace, Wener thinks these bacteria could actually clean-up the entire canal. Through interventions, “we could encourage the growth of this bacteria.”
Buildings could be designed to kill off pathogenic bacteria and support the healthy microbes in our biomes. Wener said a recent Brazilian study found pathogenic bacteria, which comes from people, thrives in closed spaces. In open air environments in the Brazilian rainforest, where lots of animals roamed through indigenous villages, there were no pathogenic bacteria, but in closed building interiors found in Brazilian cities, researchers found many. The conclusion is clear: If you increase exposure to light and air flow in buildings, you will reduce dangerous bacteria.
Through urban farming and gardening — or just plain playing in the dirt — humans can also increase their exposure to healthy microbes found in soils. A group of scientists and advocates argue that greater exposure could help fight depression and anxiety and reduce rates of asthma and allergies in both kids and adults.
The incredible increase of allergies among Western populations may be caused by our “sterile, germ-free environments” that cause our immune systems to over-react to everything from nuts to mold and pollen. Dr. Brett Finlay and Marie-Claire Arrieta even wrote a book exploring this: Let Them Eat Dirt: Saving Your Child from an Over-sanitized World.
Wener said we have created cities that reflect our fear of bacteria; instead we must create microbial-inclusive cities that improve our health. “Most microbes in our bodies have co-evolved with us. They are important to our vital functions. The future of urban planning and design should support healthy microbes.”
As part of this vision, landscape architects could design parks and plazas to be filled with accessible garden plots and soil-based play areas that let both adults and kids get dirty. We could design for holobionts instead of just people, boosting the health of the collective urban microbiome in the process.
Wener’s colleage at NYU — Elizabeth Henaff — is leading much of this research. Learn about her artful experiments. Read this article from Michael Pollan in The New York Times outlining the connections between our microbiome and health, and this Q&A from The Guardian.