This article details a radical experiment in Finland in a preschool were their yards were transformed into natural, biodiverse environments to improve children’s health. Researchers imported forest elements—like soil, wild plants, moss, and dead wood—into urban daycare centres, exposing children to rich micro-biodiversity (bacteria and fungi).

Outcome & Benefits for the Children

The study, which compared “re-wilded” nurseries with traditional asphalt and gravel playgrounds, yielded significant positive changes in the children’s internal health within a year: 

In short, the new forest environment acts as a microbial transfer system, allowing the children’s “inner biodiversity” (their microbiome) to exchange beneficial bacteria and fungi with the “outer biodiversity” of the soil and plants, leading to a stronger, more regulated immune system. 

The research discussed in the article is an intervention trial conducted by researchers in Finland to test the “biodiversity hypothesis” in an urban setting.