Americans now spend a stunning 90 percent of their time indoors. Our sedentary, screen-addicted lifestyles have been blamed for a range of ills — including obesity, attention problems, allergies and more.
We know that getting out of the house and into nature confers many benefits for physical and mental health. But there’s an additional benefit you might not know about: contact with the soil — good old dirt — enriches the gut microbiome, the community of microorganisms that inhabit our digestive tracts. A growing body of evidence shows that a healthy gut microbiome is essential for our wellbeing. Moreover, new research indicates that by restoring soil health, we can restore our internal microbial communities — a win-win for nature and human beings alike.
When I think about the protective power of dirt, I remember my own childhood. When I was released from grade school at the onset of summer, my mother would throw away my shoes and let me roam barefoot through the Indiana Dunes until Labor Day. Even though we lived not far from Gary, Indiana’s steel mills and oil refineries, there were thickets, prairie patches, and shallow marshes large enough to keep my brothers, cousins, and me occupied from dawn until dusk. During our explorations on the city’s edge, I would occasionally eat clay or rabbit scat (which I mistook for raisins), drink water straight out of Lake Michigan, or chew on leaves of wild grapes and sassafras.
You can bet it never dawned on me nor my parents that I might be enriching my gut microbiome through such audacious acts of eating on the wild side. But I was blessed by repeated exposure to myriad beneficial microbes, and no doubt some troublesome ones as well. They probably primed my immune system and protected me from all manner of diseases for many years to come.
Most of us who grew up in US cities belatedly learned of the protective interactions between diverse soil and gut biota only after we “paved paradise and put up a parking lot.” My generation was perhaps the first among Americans to suffer what journalist and author Moises Velasquez-Manoff has called an epidemic of absence.
Velasquez-Manoff coined that phrase to refer to a whole set of diseases that may be triggered by the loss of microbes in our guts and on our skin. Each of us contains multitudes: the millions of microbes in our bodies have evolved along with us, and play vital if not fully understood roles in regulating our immune systems. We do know that diminished gut microbiota, which is common in developed countries, is associated with higher rates of autoimmune disease, allergy, depression, and more.
Today, many epidemiologists, ecologists and public health experts believe that those diseases result from pervasive changes in our landscapes, in addition to the misuse of antibiotics and agrichemicals, and the barrage of toxic chemicals now pervasive in the air, in our fabrics, and in our diets.
Increasingly, they point to the rather sudden, precipitous declines of certain microbes in our bodies, resulting from our diminished contact with the fertile earth that once lay beneath our feet. The Human Urban Microbiome Initiative (HUMI) website now lists well over a dozen maladies that afflict urban youth, in contrast to their peers who grow up on farms or surrounded by wildlands.
HUMI contends that the lack of protracted contact with a wild and diverse soil microbiome may make children more vulnerable to ADHD, allergies, cancers, cardiovascular disease, depression, diabetes, inflammation-related pain, migraine headaches, muscular dysfunction, and vertigo, among other disorders.
This suite of disorders is not necessarily due to a general lack of engagement with “nature.” It is not so much about the birds and the bees, or a dearth of outdoor recreation opportunities in manicured parks. Instead, it may arise when there is a lack of frequent inoculation of the human microbiome with a diverse set of species that inhabit healthy soil.
Our access to healthy landscapes and the beneficial microbes hidden within them has been disrupted by decades of land development, habitat fragmentation, contamination and homogenization. Unfortunately, microbiomes in urban green spaces have not been well studied. But research shows that it is possible to restore degraded soil microbiomes to approximate wild, unspoiled areas. That’s why my friend James Aronson of the Missouri Botanical Garden claims that we need to mobilize a global effort to restore the health of damaged ecosystems, in ways that might just restore our own health as well.
In May, Aronson and I heard Chris Skelly, HUMI’s International Program Director, make a show-stopping statement at the kick-off meeting of the new international EcoHealth Network in St. Louis, Missouri:
“What destroys the health of ecosystems and their soil microbiome and what destroys the health of people are one and the same. So we find ourselves at a tipping point. We will now require biodiverse green spaces in urban settings to restore health to our communities…We must look beyond the conventional health care system to biodiversity to heal our ills, for conserving the diversity in our soils may be the most effective health intervention we can ever make.”
Despite the magnitude of the challenge, there is room for hope. At the EcoHealth Network meeting, Martin Breed — a scholar of ecosystem health, restoration ecology, and genomics based at the University of Adelaide, Australia — observed that much is being done, and there is more we can do to restore such green spaces to our metro areas:
“Urban restoration is the new frontier,” said Breed. “And fortunately, the healthiest thing you can do in this world is to get physically engaged in ecological restoration.”
That’s right — by getting your hands dirty planting trees or building soil erosion control structures — you are not only conserving biodiversity, you are also inoculating yourself with microbes that you yourself may need. One study found that contact with healthy soil had such a powerful effect on human health, it was equivalent to increasing socioeconomic status.
What’s more, there are other benefits from the positive social contacts and community cohesion you experience when you work to restore soil health with others of different races, classes, faiths or political persuasions. These are the “spill-over” effects of what Native American ecologist Robin Kimmerer calls reciprocal restoration: “As we work together to restore our homelands, we ourselves are restored,” she writes.
The new research has implications for how we protect and enjoy nature. As Henry David Thoreau shouted out during one of his epiphanies, our experience with the natural world requires “Contact! Contact!”
Today, our hands-on contact with nature is minimal. The wildlands and scenic rivers we once set aside as parks for our children’s health and enjoyment have become overdeveloped, filled up with sports arenas, parking lots, concrete-lined swimming pools, and sterile bleachers.
We do not need to pave every new pathway running through our parklands, nor make all our children who visit such places “stay on the trail” as they now must do even when visiting Walden Pond, where Thoreau once lived.
They need contact with the blessed earth itself: the tilth of well-managed soil; the furriness of moss- and lichen-covered rocks; the roughness of tree bark and smoothness of driftwood; the sweet-and-sour fragrances of compost; the subtle pungency of aged manures and mulches.
We need to rewild our urban sanctuaries set aside long ago as parks and forest reserves. The matrix of asphalt and cement have turned them into islands. Rather than building more roads, parking garages and hermetically-sealed stadiums on these lands, we need to restore their biological diversity, getting rid of sterile buildings, as well as intensively sprayed, meticulously mowed lawns and putting greens.
We need to plant them with native plants like Canada wild rye, sideoats grama, bluestems, and Indiangrass, and inoculate the plants with mycorrhizae. We need to sow prairie coneflowers, bee balms, wild mints, and sunflowers in their midst. We need perennialize them, so that prairie dogs and gophers can manage the soil, rather than letting tractors and rototillers and lawnmowers do that work.
And when a court determines that some “truant” youth needs to do community services to atone for his or her sins, we need to let them join a work crew of restoration ecologists who are sowing pollinator meadows, spreading compost on damaged lands, or transplanting trees for a fencerow to hold a riverbank in place.
In Patagonia, Arizona, where I now live, our Borderlands Restoration Network has engaged over 150 youth in activities like these over the last five years. The young people work five hours a day, for five weeks of their summer. Some come from the declining border towns of Nogales and Douglas, Arizona, where asphalt and cinderblocks cover more ground than mesquite and desert wildflowers. But now many of our multicultural border youth are delighted to be camping, building dams to slow soil erosion, replenishing depleted soils with compost, and gardening with their hands deep in the dirt.
These “Borderlands Earth Care Youth” have not only gotten inoculated with microbes during their work together; they have also been inoculated with hope.
Perhaps both the microbiome and hope itself regenerate and flourish when we are engaged with other lives unlike our own — lives that may otherwise hidden from our view and from our hearts.
And perhaps we need to take the awesome pledge that Wendell Berry once shaped into a beautiful chain of words: “What I stand for is what I stand on.”