Date of the last update: 27.09.2022
Photo: Slawomir Murawiec, MD
Mental health of the country’s population is influenced by biodiversity of plant and bird species, the results of a nationwide study from Germany reveals. As this is Poland’s neighbouring country, this correlation may very likely refer to Polish society, too, only there is no relevant data to confirm that.
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A study by a team of researchers led by Joel Methorst from Frankfurt am Main reports that the number of bird and plant species in the surroundings correlates with socioeconomic data on people’s mental health.
Methorst and his co-workers point out that there is a large number of studies confirming that connecting with nature is positively related to people’s health. The positive impact has been documented in relation to both mental and physical health, for example in the context of people living near urban parks or water bodies. Most of these studies, however, focus on selected aspects, such as proximity to natural places or their size. By contrast, little is known about the relationship between mental and physical health and species richness in the given area (biodiversity).
Research to date has indicated that a high bird and plant species diversity in parks and urban environment in general is related to improved psychological well-being in people. Two theories are mentioned to explain this phenomenon: ART (Attention Restoration Theory) and Stress Reduction Theory. In terms of broader health, visitors to parks with greater biodiversity reported better overall health, both in reference to mental and physical health aspects, and higher perceived restoration.
The authors also noted the effect of subjectively perceived species richness on health. Thus, it is the subjective perception of biodiversity (abundance of plant, bird and butterfly species) rather than its objective measurement that influences the psychological well-being of people visiting green areas.
The researchers decided to investigate these relationships on a country-wide level in a survey conducted all across Germany. For this purpose, the study combined macro-ecological data and socio-economic data from the German Socio-Economic Panel (SOEP). As for biodiversity assessments, the team focused on plants and birds. They considered both the number of species and quantity (abundance) of birds.
Data on the health of population across country was taken from the German Socio-Economic Panel. The data provide information on the socio-economic, demographic and health status of the German population. The data are organised territorially. The information available from this panel addressed 8 domains of physical and mental health. Factors such as population density, GDP per capita, unemployment rates and the size of the country’s different territorial units, were also taken into account.
Data on bird species richness and abundance were obtained from the “Atlas of German Breeding Birds”(Gedeon et al. 2014). The richness of bird species in a county ranged from 59 to 146, while bird abundance ranged from 1000 to 6000 breeding pairs. To assess plant species biodiversity the researchers used data on species occurrence in Germany.
The results obtained by the researchers indicate a statistically significant correlation between richness of bird and plant species in an area and inhabitants’ mental health. No such correlation was found in relation to bird abundance.
Regarding physical health, no relationship was confirmed between plant and bird species biodiversity and this dimension of health.
The study found that a short distance to public parks has a positive influence on mental and physical health, while, on the other hand, people’s health is at lower levels when they live further away from parks. If green spaces are not accessible at a walking distance, this has a definitely negative impact on physical health.
In the conclusion, the authors indicate that there is a positive relationship between plant and bird species richness in an area and inhabitants’ mental health. Thus, there is a strong and proven link between biodiversity and mental health.
These results are in line with data available in numerous previous publications, which indicate that biodiversity of plant and bird species positively affects psychological well-being of people living in a rich natural environment.
The authors also comment on the lack of effect of bird abundance on people’s psychological well-being. One possible explanation is that some common bird species, such as crows or seagulls, do not necessarily evoke positive associations in people. Consequently, in this context, it is bird biodiversity (species richness) that has an impact on people’s well-being and mental state (in the context of contact with nature discussed here).
Therefore, protecting sites that promote high species biodiversity (plants and birds) matters not only for reasons related to nature conservation, but also significantly improves human well-being and good mental health-related quality of life. This factor may positively affect population’s mental health, especially given the accumulation of highly stressful social and economic factors experienced by Europeans. As a consequence of the results obtained, the authors propose the use of biodiversity as an indicator of salutogenic (health-promoting) characteristics of natural areas, landscapes and green spaces in cities.
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Article review: Joel Methorst, Aletta Bonn, Melissa Marselle, Katrin Böhning-Gaese, Katrin Rehdanz: Species richness is positively related to mental health – A study for Germany. Landscape and Urban Planning, 2021;211: 104084
The review by: Sławomir Murawiec, MD