Finland replaces artificial playground surfaces with natural ones

SCIENCE/LIFESTYLE

In Finland, 43 daycare centres have replaced standard playground surfaces — rubber mats, gravel and plastic flooring — with natural materials, including soil, sand, moss, plants and sections of forest floor. Why? To see if it increases children’s exposure to environmental microbes through everyday play.

The Guardian reports on one site at Humpula daycare in Lahti where outdoor areas have been redesigned into small ecosystems. There, children are encouraged to dig, play in soil, use compost, and interact directly with natural materials rather than synthetic playground surfaces. In some centres, researchers even introduced imported forest floors containing living soil, moss, and native plant life.

The two-year study, led by Finland’s Natural Resources Institute, tracked 75 children across ‘rewilded’ and conventional daycare centres, analysing microbes from skin and saliva, as well as immune markers in blood samples. The results showed that, within weeks, children in biodiverse environments had fewer disease-associated bacteria — such as Streptococcus — on their skin; showed a positive change in gut bacteria linked to inflammation; and had increases in immune-regulating T-cells. Researchers also reported stronger overall immune responses compared to children using standard asphalt-and-plastic playgrounds.

The study links these changes to the biodiversity hypothesis, which suggests reduced exposure to natural microbes in early life may contribute to immune-related conditions.

The idea that modern childhood environments may be too biologically ‘sterile’ for optimal immune development is gaining popularity. The core argument isn’t that dirt is automatically beneficial; it’s that diversity of exposure matters. As one study notes, biodiversity loss in living environments can lead to “inadequate stimulation of immunoregulatory circuits”, contributing to asthma and allergies.

Children today spend more time indoors or in heavily controlled environments than earlier generations, limiting interaction with soil microbes, plants, and natural ecosystems. But in Finland, they are adopting outdoor learning that takes place year-round — regardless of the weather. These programs encourage direct contact with natural materials in everyday play and education.

And it’s not just in education. Some researchers are now introducing the concept of “probiotic cities”, arguing urban environments should be designed using bio-integrated materials and microbiome-aware landscaping to promote healthier ecosystems and support improved immunity. The findings also tie into broader conversations about mental health and spending time outdoors.

Children used to grow up in constant contact with natural environments, learning about soil, plants, animals, and the microbes that come with them. In many urban settings today, that exposure is far more limited, replaced by sanitised surfaces, indoor routines, and highly controlled outdoor spaces. What makes the Finnish findings important is that they suggest these environmental differences may show up in measurable ways. If early exposure to biodiverse settings influences immune development, then it adds weight to a growing body of research linking modern, low-microbial environments with rising rates of allergies and immune-related conditions.

It’s more than about health and wellbeing. Urban design, education spaces, and city planning all play a role in how much contact children have with natural systems during key stages of their development. The question is whether removing living systems from everyday spaces entirely has unintended consequences. At the same time, researchers are still cautious. These findings don’t prove a single cause-and-effect relationship, and long-term effects are still being studied. But the pattern is consistent enough that it’s pushing more attention toward how ‘clean’ modern environments should actually be.

Urban design, education spaces, and city planning all play a role in how much contact children have with natural systems during key stages of their development. The question is whether removing living systems from everyday spaces entirely has unintended consequences.

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