Research supports a positive connection between urban greenspace and human health across the age span. The pathways in which greenspace benefits health, however, are unclear. This report provides a framework to demonstrate the many potential pathways by which greenspace can beneﬁt health. The potential pathways are organized into three domains: reducing harm, restoring capacities, and building capacities. This report also includes a discussion of the potential challenges and opportunities of greenspace research and provides recommendations for future research eﬀorts.
Examples of how urban greenspace can reduce harm to human health include reducing exposure to air pollution, noise and heat. Residences and schools with higher surrounding greenness have lower traﬃc-related air pollution exposures. This, in turn, benefits children's health and development, including cognitive development. Surrounding greenness also has a cooling eﬀect on urban environments, reducing heat-related mortality.
The restoring capacities of green space include attention restoration and physiological stress recovery -- referred to in the environmental psychology literature as stress reduction theory (SRT) and attention restoration theory (ART). SRT is based on the idea that viewing vegetation and other natural-appearing environmental features can evoke positive emotions that block negative thoughts and emotions. These responses shut down the stress response which includes negative hormonal, cardiovascular and musculoskeletal parameters. ART is based on the understanding that vegetation and other natural-appealing environmental features attract and hold a person's attention without eﬀort. This form of attention allows the neurocognitive mechanism involved in eﬀortful directed attention to rest.
The building capacities of green space include the way green space encourages physical activity and facilitates social cohesion. These capacities have implications for healthy child development. Outdoor play not only promotes more physical activity than indoor play, but also provides varied opportunities for social interactions, which support socio-emotional development and social cohesion.
The impact of green space on human health may vary by population group. Some studies, for example, indicate that the beneﬁcial associations between greenspace and health are strongest for those with low socio-economic status (SES) and those living in more deprived neighborhoods. Size, quality, and location of green space can also impact potential outcomes. Larger greenspace with fewer opportunities for surveillance can serve as a place for crime or as a place feared due to the potential for crime. This can be especially troublesome for vulnerable populations, including women, children and the elderly. Young children and senior citizens – due to limited mobility options -- may also depend more on nearby greenness for engagement with nature than other population groups.
Existing evidence affirms beneficial impacts of greenspace on health and supports possible pathways linking greenspace to health. More research is needed, however, to gain a better understanding of how such benefits may vary by context, population groups, and health outcomes. This report offers recommendations for further research with the goal of generating new evidence to guide policy makers in making full use of the various potential beneﬁcial impacts of urban greenspace on a large range of health factors.