Areas with higher numbers of well-arranged trees have lower mortality rates than areas with more sparse coverage. The findings were published in The Lancet Planetary Health.
Duration and frequency of contact with green spaces have been linked to better cardiovascular health, mental health, and general health. Although tree clusters constitute a major part of green spaces, until now, nationwide longitudinal studies investigating the link between residential tree canopy configuration and mortality have not been conducted.
In the current study, researchers analyzed high-resolution tree canopy data within a radius of 500 meters of a person’s area of residence alongside mortality data from 6.2 million Swiss adults collected between 2010 and 2019. Canopy data included the total area covered by all tree clusters as well as their proximity, connectedness, geometrical complexity, and level of fragmentation.
Ultimately, the researchers found that tree canopy cover and their spatial arrangement correlated with mortality. Neighbourhoods with large, contiguous, and well-networked areas of free canopies had a significantly lower mortality risk than neighborhoods with fewer fragmented areas of tree canopies with complex geometries. The link was especially evident in densely-developed peri-urban urban areas with poor air quality and high temperatures.
They additionally found that the effects of tree canopy coverage and mortality varied by cause of death and buffer size. For example, while greener areas may benefit mental health and neurological conditions, they may not always have the same protective effects for cardiovascular health. This, the researchers noted, indicates that tree canopy configuration may affect different diseases via different pathways.
"Although we can't yet define a direct causal link, when we have addressed factors such as age, gender and socio-economic status, the data shows clear correlations. Our results provide plausible indications that human health may be influenced not only by the quantity of trees but also by their spatial distribution,” said first author of the study, Dengkai Chi, a postdoctoral researcher of Comparative Ecology of Cities at the Swiss Federal Institute of Technology in Zurich, in a press release.
The study provides ' valuable insights into optimizing forested greenspaces' and 'should be of interest to policymakers and designers of urban greenspaces,' wrote the researchers in their study.
Sources: Science Daily, The Lancet Planetary Health
