How forests can benefit our health

Tree canopy density as a factor

‘Our study clearly shows that the health benefits of forests depend heavily on the characteristics of the respective forest ecosystems and that forest managers can use local conditions and needs to design forests in such a way that, in addition to other forest functions, the health and recreational functions of forests can also be promoted,’ says Prof. Dr. Michael Scherer-Lorenzen, Professor of Geobotany at the University of Freiburg and coordinator of the project. ‘This is particularly important for the development and design of so-called spa and healing forests.’

The scientists were able to show that forest structure is the most influential factor for health effects, in particular tree canopy density and the ratio of stem area to basal area in a forest. However, there is no ideal density level, as a particularly dense forest has disadvantages as well as health benefits.

Better air quality, less particulate matter, fewer ticks

A dense canopy reduces heat stress by providing more shade and creating a more stable microclimate. This effect is particularly important in urban areas, where heat waves occur more frequently. It also improves air quality by increasing the leaf surface area available for the deposition of fine dust, which has been shown to reduce air pollutants. However, a dense canopy also means that less light reaches the forest floor, which can hinder the growth of medicinal plants that are beneficial to health. It also increases the risk of Lyme disease transmission because the higher humidity in the forest favours the presence of ticks.

According to the study, tree species diversity has a rather weak but positive effect on health and well-being. Increasing tree species richness is therefore a safe and beneficial measure for forest managers, offering numerous advantages beyond human health, such as promoting associated biodiversity beyond trees. The perceived biodiversity of a forest, in turn, has a significant impact on people’s psychological well-being. They experience a forest as healthier if they perceive it as diverse, even if this is not reflected in the actual tree species diversity.

Forest bathing. Photo: Aurore Delsoir

Health benefits depend on local priorities

Among other things, Scherer-Lorenzen’s team in Freiburg contributed to determining the health effects of so-called soundscapes, i.e. sound landscapes, and showed that structurally rich forests have a diverse soundscape, which in turn has a positive effect on recreational function. “Overall, it was particularly exciting for us to coordinate such a diverse and interdisciplinary team of scientists and to incorporate the different perspectives from the natural sciences, psychology and medicine into the project planning and evaluation of the results,” says Scherer-Lorenzen.

The study offers practical guidance for forest management and urban planning and provides policy makers and forest managers with concrete strategies for designing forests that are tailored to the specific health needs of different regions. “Our results show that there is no such thing as an ‘ideal forest.’ The health benefits of a forest always depend on local priorities,” explains Scherer-Lorenzen. In urban environments, for example, reducing heat and improving air quality may be priorities, while in rural landscapes the focus may be more on reducing the prevalence of Lyme disease and increasing the yield of medicinal plants.