Biodiversity can provide mental health benefits.

Biological diversity in city parks and green spaces can have psychological benefits for humans, according to a new study from the United Kingdom. The researchers found that visitors to city parks with a greater diversity of birds, butterflies, plants, and other organisms reported feeling better than visitors to less-diverse green spaces. Such findings have important implications for urban planning and policy as the human population becomes increasingly urbanized, the study concludes.

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Lead author Richard Fuller and colleagues at the University of Sheffield analyzed levels of biodiversity at 15 parks and green spaces across the U.K., then questioned visitors on whether their outings helped them clear their minds, gain perspective, think easily about personal matters, or feel connected with nature. Visitors to places with greater biodiversity not only felt better, but were able to fairly accurately estimate the level of diversity in the area. "Public urban greenspaces provide one of the few avenues for direct contact with the natural environment," the researchers write, adding that "such contact has measurable physical and psychological benefits."

Earlier studies point to similar conclusions. A nine-year survey of U.S. gall bladder patients showed that patients recovered faster and required less pain medication if their hospital windows overlooked trees rather than brick walls. Other research indicated that inner-city residents who had some nearby nature outside their apartments showed significantly lower levels of aggression and violence. Similarly, workers in buildings that contained plant life were found to concentrate better and feel less anxiety on average than those working without plants.

Fuller's team found that the restorative benefits of biodiversity increase with the species richness of urban green spaces. As a result, the study concludes, successful management of these spaces "should emphasize biological complexity to enhance human well-being in addition to biodiversity conservation."