• Making outdoor play areas greener and more biodiverse could improve children’s immune systems in just one month, according to a new study in Finland.
  • City playgrounds were covered in forest undergrowth and lawn turf.
  • A growing body of evidence supports the health and well-being benefits of nature.

Making outdoor play areas greener and more biodiverse could improve children’s immune systems in one month, a new study suggests.

Scientists in Finland covered the playgrounds of city preschools with forest undergrowth, lawn turf and planter boxes.

Environment biodiversity health children play areas
One example of a greener play area found to improve children's immune systems.
Image: Natural Resources Institute Finland

After 28 days, the experimental study found the children (aged three to five) in the modified playgrounds appeared to have a greater diversity of microbes on their skin and in their guts than those children in playgrounds surfaced with paving, tiles and gravel. It says this could improve the regulation of their immune systems.

Although the Finnish experiment was small – involving only 75 children at 10 venues – Aki Sinkkonen, research scientist at the Natural Resources Institute Finland, who led the work, says the results are strong and that further studies are now underway.

“The yard areas of all daycare centres should be transformed into green areas,” Sinkkonen says, “because this will improve the regulation of children’s immune systems in only a month.”

Soil bacteria diversity
The diversity and richness of bacteria was markedly greater in the playgrounds with forest turf.
Image: Science Advances

The ‘biodiversity hypothesis’

When we are in contact with nature, we expose ourselves to a broad range of microbes, activating different parts of our defensive system, the study explains. Reduced contact with natural environments and biodiversity, however, may adversely affect the immune system – this is known as the ‘biodiversity hypothesis’.

The Finnish researchers say their findings support the idea that low biodiversity in modern living environments could lead to “uneducated” immune systems and an increased prevalence of immune-mediated diseases.

Environment biodiversity health children play areas
Greener play areas improve biodiversity as well as improving the immune systems of children who play there consistently.
Image: Natural Resources Institute Finland

Previous studies have found that children who live in rural areas and who are in contact with nature have a lower probability of catching an illness resulting from disorders in the immune system, says Sinkkonen.

The number of autoimmune diseases – where the immune system attacks the body – is on the rise in developed nations. The conditions include type 1 diabetes, multiple sclerosis, rheumatoid arthritis, lupus and coeliac disease.

While the underlying cause of autoimmune disease is still unknown, the most common theory, according to Harvard Medical School, is that a particular genetic background makes certain people prone to immune-system “misfiring”. So when they encounter an environmental trigger – such as an infection or toxin – this sets off autoimmune disease.

The health benefits of being in nature have long been promoted around the world. For example, “forest bathing” – essentially, being in the presence of trees – has been part of the public health programme in Japan since the 1980s.

Spending at least 120 minutes a week in nature is associated with good health and well-being, according to research led by the European Centre for Environment and Human Health in the UK.

Writing in the journal Nature, the report’s authors say: “A growing body of epidemiological evidence indicates that greater exposure to, or ‘contact with’, natural environments (such as parks, woodlands and beaches) is associated with better health and wellbeing, at least among populations in high income, largely urbanized, societies.”


What is the World Economic Forum doing to promote sustainable urban development?

Cities are responsible for 75% of global greenhouse gas emissions and are home to over half of the world’s population—a number that will grow to two-thirds by 2050. By going greener, cities could contribute more than half of the emissions cuts needed to keep global warming to less than 2°c, which would be in line with the Paris Agreement.

To achieve net-zero urban emissions by 2050, the World Economic Forum is partnering with other stakeholders to drive various initiatives to promote sustainable urban development. Here are just a few:

To learn more about our initiatives to promote zero-carbon cities and to see how you can be part of our efforts to facilitate urban transformation, reach out to us here.

Writing in the journal Nature, the report’s authors say “a growing body of epidemiological evidence” suggests greater exposure to places such as parks, woodlands and beaches increases health and well-being – “at least among populations in high income, largely urbanized, societies”.

In adults, living in greener urban areas is associated with lower probabilities of cardiovascular disease, obesity, diabetes, asthma hospitalization, mental distress and, ultimately, mortality, the report says. In children, the associated outcomes are lower risks of obesity and myopia (short-sightedness).