Urban green space next to the Vistula River in Kracow, Poland, 2023.
Photograph by Alessio Russo.

By F. Beute, M.R. Marselle, A. Olszewska-Guizzo, M.B. Andreucci, A. Lammel, Z.G. Davies, J. Glanville, H. Keune, L. O’Brien, R. Remmen, A. Russo, and S. de Vries.

Read the full paper here.

Cities are growing all around the world but the availability of urban green space (trees, plants, grass, vegetation) is shrinking. Research indicates that exposure to green space can improve mental health in multiple ways. But with less area available for green spaces in cities, we need to know which types of green spaces (e.g., park, forest) and which characteristics of green space (e.g., the density of the vegetation, openness, sounds) can improve mental health most. To understand this, we need to compare the mental health benefits of these different types and characteristics of green space.

Therefore, we conducted a scoping review and made an overview of studies that enabled this comparison between green space types and characteristics. In total, we found 215 papers. One of the most striking outcomes of our review is that only very few studies have compared the effects of different types or characteristics directly, meaning that they, for instance, compared a visit to the park with a visit to the forest. Many studies looked at different types or characteristics but did not directly compare them. For instance, a number of studies looked at the amount of grass and trees within 500 meters of the home. They looked at the effects of grass and trees separately, but did not investigate whether one was better than the other.

A second main finding of our review was that the studies were very different in terms of how they were designed and executed, and that they also differed greatly in where they were conducted. We found that these differences sometimes were systematic and specific for certain green space comparisons or green space types. For instance, the studies that did directly compare green space types were all experiments, looking at the effects of short-term visits to nature (e.g. 15 minutes) on short-term mental health outcomes (i.e., mood or stress).

Therefore, with the studies that have been conducted so far, we can’t conclude yet which green space type or characteristic is most important for mental health. Future studies are needed to enable this comparison.