Urban forests contribute to human health by reducing harm, restoring capacities, and building capacities

Wolf, K. L., Lam, S. T., McKeen, J. K., Richardson, G. R. A., van den Bosch, M., & Bardekjian, A. C. (2020). Urban trees and human health: A scoping review. International Journal Of Environmental Research And Public Health, 17. https://doi.org/http://dx.doi.org/10.3390/ijerph17124371

Urban forests are comprised of diverse tree species and vegetation structures distributed across public and private properties throughout a city. Urban forests provide multiple services in the environmental, economic, social and health dimensions of the city. While these services and related benefits have been studied and analyzed in literature reviews, to date no review has focused specifically on how trees in urban areas affect human health. This scoping review addressed this gap in the literature.

An initial search identified over 3000 related peer-reviewed articles. After duplicate, non-relevant, and studies not published in English were removed, the list was reduced to 201 studies. These studies were conceptually sorted into three categories: Reducing Harm, Restoring Capacities, and Building Capacities. Reducing Harm addressed such concerns as air pollution, ultraviolet radiation, heat exposure, and pollen. Topics relating to Restoring Capacities included attention restoration, mental health, stress reduction, and clinical outcomes. Building Capacities included such topics as birth outcomes, active living, and weight status.

While the literature search placed no limitations as to when the studies were published, all the included studies were published since 1980. Most of the studies (96%), however, were published since 2000, and many in 2010 or later. Approximately one third of the studies were based in North America, one third in Asia, and one fourth in Europe. The remaining studies were based in Australia and South America. While studies addressed all ages, most of the studies focused on adults. Only 13% of the studies focused on children. Eighty-two of the 201 studies were classified within the Reducing Harm domain, 63 in Restoring Capacities, and 56 in Building Capacities. While studies across all three categories (Reducing Harm, Restoring Capacities, Building Capacities) incorporated the full range of tree settings, some types of tree settings appeared more frequently in certain domains than in others. Forest immersion, for example, is associated predominantly with Restoring Capacities, while canopy/land cover was used more often in studies categorized as Reducing Harm and Building Capacities.

The findings of this review support the understanding that exposure to trees is associated with improved human health for people living in urban environments. Urban forest planning and management should thus “strategically promote trees as a social determinant of public health.”

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