In an intervention-based study of 10 urban daycare centers in Finland, adding biodiverse material from the forest floor and sod to daycare yards diversified children's environmental and skin microbiota and made positive changes to immune functioning.
Roslund, Marja I. et al. “Biodiversity intervention enhances immune regulation and health-associated commensal microbiota among daycare children.” Science Advances 6, no. 42 (2020). https://www.science.org/doi/10.1126/sciadv.aba2578
