Forests play a crucial role in promoting health and wellbeing, but not all forests provide the same benefits. A large-scale international study, co-led by the University of Surrey and the University of Ghent, demonstrates how specific forest characteristics – such as canopy density and tree species diversity – can affect various health outcomes.

The research, published in Nature Sustainability, was carried out by a range of international partners within the Dr. Forest research project, investigated 164 forests across five European countries, offering valuable insights for forest management and urban planning. The study examined seven ecological characteristics of forests and their influence on different human health effects.

Tree species diversity was found to have a limited but positive effect on human health and wellbeing. Increasing tree species diversity is therefore considered a safe and beneficial intervention for forest managers, which also provides multiple co-benefits beyond human health, such as supporting associated non-tree biodiversity.

Forest structures – particularly, the canopy structure – were found to have the strongest health impact, both with its own benefits and drawbacks. Dense canopy reduces heat stress by providing more shade and creating a more stable microclimate, while also improving air quality by increasing leaf surface area for fine particulate matter deposition – both crucial elements in urban areas where heatwaves and airborne pollutants are more frequent.

On the other hand, a dense canopy can also increase the risk of Lyme disease – as ticks thrive in humid climates – and lead to less light reaching the forest floor, which can hinder the growth of medicinal plants, affecting their potential health benefits.

From a mental health standpoint, just being in a forest was found to be beneficial, reducing anxiety and stress, and increasing positive emotions. Forests that people perceived to be more biodiverse and natural were also found to be the most beneficial for mental health.

Dr Melissa Marselle, Lecturer in Environmental Psychology at the University of Surrey, said:

“Our study shows that forests generally provide a mental health benefit, reducing anxiety and stress, regardless of their biodiversity or structure. As one in six people in England experience anxiety and depression each week, this research suggests that simply being in a forest can improve mental health. For the UK, this means preserving urban forests so people can easily access forests where they live, work and play for their mental wellbeing. Contact with forests could be prescribed by the NHS, as research shows that NHS nature prescriptions are effective at improving mental health.”

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