The quality of urban green spaces depends not only on their area but also on biodiversity. The results of the published study confirm that the abundance of plant species, the preservation of urban forests and meadows, and species-rich kindergarten yards can increase environmental microbial diversity and thereby support children's health.
The study, led by Professor Meelis Pärtel, looked for a connection between the biodiversity of the urban environment, especially bacteria found in soil, and the risk of allergies in children, and was centered on the biodiversity hypothesis, according to which exposure to diverse environmental microbes helps shape the immune system and reduces the likelihood of allergies and other inflammatory diseases. The authors, including Polina Degtjarenko, a Researcher in Restoration Ecology of the Landscape Biodiversity Workgroup, and the Head of the Workgroup, Professor of Restoration Ecology Aveliina Helm, focused on bacteria belonging to the Gammaproteobacteria class, which is considered a particularly important microbial group in the development of the human immune system.
The study used data from 148 children in Tartu, collected as part of the DIABIMMUNE project led by pediatricians atTartu University Hospital. The children were assessed for atopy, or the tendency to develop allergic diseases. For this purpose, the level of IgE antibodies against various allergens in the blood was measured at different ages. At the same time, an extensive urban soil study was conducted in Tartu, during which samples were collected from 743 green areas. The sample areas included city parks, forests, meadows, lawns, gardens of private houses, and kindergartens' yards. The soil samples were analyzed for bacterial and plant diversity using DNA-based methods.
The most important result of the study was that children living closer to green areas with high Gammaproteobacteria diversity were significantly less likely to develop atopy. Conversely, the risk of allergies increased when such areas were located further from home. The effect remained statistically significant even after accounting for other possible factors, such as land use and socioeconomic differences between city districts. The study also showed that atopy was more common in wealthier neighborhoods. The authors suggest that this may be related to less exposure to natural diversity and more intensive gardening and chemical use.
Another important finding from the study was that the abundance of urban meadows around children's homes also reduced allergy risk. According to the authors, open grasslands may facilitate the spread of microbes through the air and provide greater biodiversity than intensively maintained lawns. Species-rich green spaces may also improve well-being and reduce stress, which in turn supports immune function.
Special attention was paid to the outdoor areas of kindergartens. It turned out that the soil in kindergartens contained more species of Gammaproteobacteria than in ordinary public green spaces. A possible reason is the more diverse conditions that arise in the soil when children come into contact with them, as well as the microbes that children themselves spread into the environment. The result is important because early exposure to diverse microbes can support the normal development of the immune system.
The authors of the article emphasize that this is an observational study and a direct causal relationship cannot be fully proven. In addition, it was not possible to assess all possible influencing factors, such as children's daily habits, diet, or how much time they actually spent in green spaces. However, the results support previous studies in this area, which prove the close connection between the natural environment and microbial diversity in the prevention of allergies.
The article can be read here: https://doi.org/10.1016/j.ufug.2026.129514.
The photos show 133 children from Tartu Maarjamõisa kindergarten sowing seeds in the Maarjavälja urban nature experimental area. Photos by: Mana Kaasik
