As parents know, taking young children to the forest for camping, hiking, and recreation is a great way to relax and create family memories. The mental benefits of such excursions help offset the stresses of city life. New research shows that the benefits to children may be more extensive than we realize. Playing in forests appears to confer health gains and enhanced learning.
For the first time in the history of humanity, most children are being raised in dense metropolitan cities. This population demographic shift has led to a dramatic increase in immune-mediated diseases.1 Of these diseases, the most common are colds, cases of flu, bacterial infections, allergies, asthma, and autoimmune and skin disorders. Ironically, the nations with the greatest wealth and the highest hygiene levels manifest the largest increases in immune-mediated diseases.
The leading hypothesis to explain this enigma is that young children raised in relatively wealthy urban environments are exposed to a much lower biodiversity of microbes than children who were raised previous to the advent of the industrial revolution in the mid-1700s.2 However, this hypothesis, until a few months ago, had not been put to experimental trials via human intervention.
Environmental Diversity Experiments
A team of seventeen clinical microbiologists and ecologists, known as the ADELE Research Group, performed the research study. It was the first human intervention trial where environmental biodiversity was manipulated to examine the effects on the microbiome (the collection of microorganisms in our body) and the immune system of young children. The group conducted a 28-day biodiversity intervention on children in three distinct daycare environments in Finland: one in a standard urban daycare center, a second in an urban daycare center where the children were occasionally exposed to biodiversity elements, and a third in a nature-oriented daycare center where children visited nearby forests on a daily basis.3 The study involved 75 children aged 3 to 5 years.
Before and after the 28-day intervention the ADELE researchers measured skin and gut microbiota, plasma cytokine levels, and blood Treg frequencies in the 75 children.4 The ADELE team’s measurements affirmed an earlier experimental outcome showing that the type of ground cover and garden vegetation impacts the gut microflora of humans who live near the ground cover and vegetation.5
The ADELE team observed a dramatic difference between children who visited and played in forests on a daily basis and children who were constrained to an urban environment. Children allowed to play daily in forests experienced an enhanced and more diverse microbiome and improved functionality in their immune system. Specifically, the forest children had a higher diversity of beneficial skin microbiota, especially among Gammaproteobacteria. They also had (1) a higher ratio of plasma cytokine IL-10 to plasma cytokine IL-17A, and (2) a positive association between Gammaproteobacterial diversity and Treg cell frequencies in their blood. These latter two outcomes imply that the forest children gained stimulated immunoregulatory benefits.
In addition to the health benefits, the ADELE Research Group noted that the forest children experienced enhanced learning. Evidently, the forest provided multi-sensory exploration and diverse learning situations.
Measurements on the second control group, the children in the urban daycare center where the children were occasionally exposed to biodiversity elements, revealed that only limited benefits arise from allowing them to visit and play daily in urban green areas. These urban green areas are often contaminated by pests and pathogenic microbes and offer much less biodiversity exposure than natural forests.
Behavior Patterns of Young Children
The ADELE Research Group’s experimental results seem consistent with the behavior patterns of young children. In the neighborhood where I grew up in Vancouver, British Columbia, there were four heavily forested vacant lots less than a hundred yards from our house, a forested ravine another hundred yards farther, and a large forested swamp area a half-mile away. There were also city parks within easy walking distance. Neither I nor any of the other children in our neighborhood cared much for the manicured parks. We spent virtually all our playtime in the wild forests.
We also did not want adult supervision. We only wanted to go into the forests when there were no adults around. I now know that the lack of adult supervision meant that we got exposed to a much broader range of microbial biodiversity.
My experience as a young child, I believe, is not unique. I and others have observed that children everywhere seem naturally drawn to forests. Now that the health and learning benefits of exposing children to forests have been established, it would behoove us to find ways of ensuring that children raised in heavily urbanized environments experience regular recreational times in forests. Such exposures also bring about spiritual benefits. Wild nature declares the existence, glory, beauty, and love of the Creator.
- Michelle M. Stein et al., “Innate Immunity and Asthma Risk in Amish and Hutterite Farm Children,” New England Journal of Medicine 375, no. 5 (August 4, 2016): 411–21, doi:10.1056/NEJM0a1508749; Anita Kondrashova et al., “The ‘Hygiene Hypothesis’ and the Sharp Gradient in the Incidence of Autoimmune and Allergic Diseases between Russian Karelia and Finland,” Apmis Journal of Pathology, Microbiology, and Immunology 121, no. 6 (June 2013): 478–93, doi:10.1111/apm.12023.
- Tari Haahtela, “A Biodiversity Hypothesis,” Allergy: European Journal of Allergy and Clinical Immunology 74, no. 8 (March 2019): 1445–56, doi:10.1111.all.13763; Anirudra Parajuli et al., “Urbanization Reduces Transfer of Diverse Environmental Microbiota Indoors,” Frontiers of Microbiology 9 (February 5, 2018): id. 84, doi:10.3389/fmicb.2018.00084.
- Marja I. Roslund et al., “Biodiversity Intervention Enhances Immune Regulation and Health-Associated Commensal Microbiota among Daycare Children,” Science Advances 6, no. 42 (October 14, 2020): 3aba2578, doi:10.1126/sciadv.aba2578.
- Plasma cytokine are small proteins involved in cell signaling that play critical roles in immune response systems and Tregs are regulatory T cells with a unique role in suppressing aberrant pathological immune responses in autoimmune diseases.
- Anirudra Parajuli et al., “Yard Vegetation Is Associated with Gut Microbiota Composition,” Science of the Total Environment 713 (April 15, 2020): id. 136707, doi:10.1016/j.scitotenv.2020.136707.