In Defense of Dirt: Rewilding Our Children
Before their Bodies Forget

 From Finnish forest floors to Michigan creek beds, the science is clear:
real dirt is medicine, memory, and the immune system’s original teacher

By Thom Hartmann, author, speaker, activist, and educator

I grew up on the edge of Lansing, Michigan, with a stream just down the road and woods that felt like a secret frontier. We all did: the neighborhood kids, barefoot in the damp grass after rain, boots mucked up with creek-silt, hands scrubbed raw from climbing fallen logs and digging in the undergrowth. Getting in the dirt was part of childhood. We didn’t ask permission from microbes.

So when I read the recent report in The Guardian about Finnish nursery experiments transforming children’s health by simply letting them play in real soil, sand, leaves and forest-floor, I felt the past crash into the present and I knew again that the story of our species and our health lies in that innocent, messy contact.

In Finland, at a daycare center in Lahti (north of Helsinki), the researchers from the Natural Resources Institute of Finland adopted a radical experiment: rip out the asphalt, dig into the soil, roll out a live carpet of forest-floor moss and blueberry bushes, build compost heaps for children to feed, invite the kids to play, dig, muddle, get their hands in it.

The result, in a two-year study of three- to five-year-olds, was striking: children in the “rewilded” yards had fewer disease-causing skin bacteria (like Streptococcus) and showed stronger immune regulation (increased T-regulatory cells) within weeks. Gut microbiomes were healthier, inflammatory-associated Clostridium levels dropped.

This is the antithesis of today’s “modern” societal perspective on childhood and nature.

On the one hand, we have the modern obsession with pristine, sanitized lives: rubber-surfaced playgrounds, plastic mats, antibacterial everything. On the other, there’s the simple fact that our inner biology, our immune systems, our gut and skin microbiomes, were forged in the wild: the wild of forest floors, streams, soils, plants, bugs.

As I argued in my earlier essay “It’s All One Thing – The Story of the Worms” here in Wisdom School, our estrangement from that substrate is the seed of auto-immune disorders, of chronic inflammation, and a body that’s forgotten it’s actually part of nature.

In Michigan I was lucky: the woods and stream were mine for the exploring. I remember fingers crawling over moist logs, the smell of leaves turning, the damp cold run-off water slipping under my boots. I didn’t know at the time that those experiences were more than play: they were calibration.

They were training my immune system, teaching my skin and gut to know what nature looked like and smelled like and felt like. To know that dirt is not an enemy. And those childhood experiences are probably why I’ve never been troubled by autoimmune disorders or asthma.

So let’s call this what it is: a radical restoration. Not of some exotic wilderness, but of our lost contact with the natural microbial terrains that co-evolved with our species. The Finnish results are more than a Kindergarten trend; they’re a signal of what our children—and we all—are missing.

Here are some of the stakes:

• When kids play in dirt rich with soil microbes, their immune system steps into a healthier balance: fewer disease-causing bacteria on the skin surface, greater regulation of internal immune responses.

• The “outer layer” of biodiversity—soil, plants, forest floor—directly influences the “inner layer” of biodiversity in our bodies, our skin, gut, and airways. This is co-evolved, not incidental.

• The modern shift away from exposure—to “sterile” play surfaces, indoor confinement, sanitized surfaces—may appear benign, but it’s been quietly shaping the epidemic rise of allergies, auto-immune disorders, and inflammatory diseases that both disturb the quality of life and can shorten lifespan itself.

• This is not just personal wellness: it’s ecological and societal. The health of children, the immune burdens we carry, the resilience of future generations: all of this ties back to whether we let the next generation touch the living earth.
  

• In the Finnish classroom yard they said: “We’re moving the action from inside to outside. We want to show the children nature so they learn about it.”

That sentence is packed. Show the children nature. Let them learn through contact, through play, through mess. Not as a museum piece, not as a “nature corridor” behind a fence, but as the ground they run on, dig in, climb across, whose bugs and fungus mix with theirs.

So, I want to issue a personal call to you—if you have children, nieces, nephews—or if you’re planning for grandchildren—or if you’re simply human, who used to feel the dirt under your fingernails and the creek cold on your shins—do this: Let the next generation get messy.

Plant a compost heap. Bring real soil into the sandbox. Create a border of moss and stones. Let the rain puddle, let the bugs crawl, let the children burrow. Let the forest floor not be exotic but ordinary.

I remember that stream down the road from the house I grew up in, the woods on the edge of Lansing, the sticky Michigan clay, the little fish, frogs, and crawdads under rocks, the mud mixing into water. I remember coming home with smudged socks, grass stains and a face kissed by sap.

I didn’t know at the time that I was feeding my immune system. I simply knew I was alive and it was a thrill.

We’ve forgotten that aliveness. Our culture has prized immaculateness, separation from the “dirty” wild, the exclusion of microbes like we exclude strangers. Yet the wildness is in us. The soil is in us. We’re made of the same living matrix as the tree roots and the beetles and the moss. Broken contact with that matrix isn’t harmless: it’s a literal loss.

In the wise old words I referenced in “It’s All One Thing”: “When we remove ourselves from that web of life, we do so at our own peril.”

The Finnish story is not just cute or scientific: it’s urgent. Rebuild our contact with the living earth. Let children scoop sand and soil, let them bury their hands, let them build mud-cakes like Aurora in Finland’s day-care. Laugh as they smear soil on their faces. It’s not chaos: it’s calibration.

Yes, modernization has brought us many gifts. Clean water. Sanitation. Vaccines. But modernization taken too far, with too much separation from our biological roots, leaves us with immune systems that misfire, bodies that mistake harmless soil microbes for threats, children who never taste actual dirt. The Finnish experiment is clear: get back to the soil, get back to the forest floor, get back to the messy, ordinary earth.

And the earth—our living earth—benefits too. More forest-floor carpets. More compost heaps. More kids playing outside, fewer rubber mats, fewer sterile boxes. We begin to treat biodiversity as not just glamorous (rainforests, coral reefs) but local (yard patches, old tree stumps, rain puddles). We begin to remember that our health is tied to the health of that biodiversity.

So my invitation to you: On your next weekend, find a patch of ground the kids (or you!) can mess with. Dig into it. Feel the soil. Let a leaf rot into the compost. Let worms do their work. Let the world pull you back. Because we’re not apart from nature: we are nature. And when we pretend otherwise, we hurt ourselves and the world around us.

It’s time to stop treating microbes as abstract threats or invisible villains. They are—and have always been—our companions, our allies, our ancestral family. The Finnish children’s laughter in the sandy forest-floor yard is our ancient laughter too.

Let’s dig in.

—Thom Hartmann, educator and commentator, is the author of many respected books. Reprinted with permission. To receive new Wisdom School posts you can become a free or paid subscriber of this reader-supported digital publication, The Wisdom School: What It Means To Be Human. All Wisdom School articles are free and available to everyone. Copyright by Thom Hartmann, 2025.