Compared to rural dwellers, individuals living in urban environments have a higher incidence of immune-mediated diseases like autoimmune, inflammatory, or allergic conditions. Rural environments often have greater diversity in lifeforms and habitats, whereas urban areas show reduced overall biodiversity yet higher levels of pathogens, pollutants, and manmade materials. These alterations in living environs have been found to correlate with changes in immune cell activation and gut microbiome composition that may help explain why certain patterns of immune intolerance have become relatively common. Most children in developed societies now live in urban areas with limited access to natural biodiversity.
Residential ground cover and vegetation are known to influence human gut microflora composition, and early life contact with animal, plant, and microbial diversity is associated with immune tolerance. Regular and sometimes intensive exposure to a wide spectrum of plants, microbes, animals, fungi, invertebrates, and other life forms in natural settings repeatedly exercises regulatory pathways of the immune system, moderating overall immune reactivity and promoting tolerance. Increased time spent outdoors may also improve physical activity and elevate mood and feelings of vitality, and all of these benefits should be taken into account in urban planning.
In this study, 75 urban-living children aged 3-5 years and attending daycare during weekdays were assigned to three study groups according to the outdoor landscaping arrangements at their daycare centers:
Nature-oriented daycares provided children with daily visits to nearby forests;
Intervention daycares were provided enriched outdoor space coverings of forest floor vegetation (mainly from heather, moss, and berry plants), peat blocks, sod, and planters;
Standard daycares provided typical outdoor areas having little or no green space, and served as the control.
Children played in these outdoor areas for an average of 1.5 hours each weekday over a 28-day period, and had direct contact with the natural and/or manmade materials in the designated study spaces. Researchers sampled and analyzed the children’s skin and gut microbiota, plasma cytokines, and regulatory T immune cell counts before and after the 28-day intervention. Environmental microbiota for the Standard and Intervention outdoors spaces were also sampled and analyzed.
Exposure to Forest Biodiversity Encourages Immune Regulation
Time spent in natural outdoors settings is a crucial immune-regulating experience for urban dwellers, and especially for children. Direct exposure to forest biomes—or even just forest floor vegetation and dirt—is an effective means of altering balance among circulating immune factors (interleukins, regulatory T cells, etc.) that are key to developing immune tolerance. Biodiversity intervention is of growing importance for the management of dysbiosis and immune imbalance.