Nearby green space and human health: Evaluating accessibility metrics

More evidence-based nature accessibility metrics are needed for developing healthy urban neighborhoods

This review paper is based on the research-based understanding that nature positively contributes to human health and well-being. This paper is also based on the premise that for the design of healthy cities, appropriate accessibility metrics are needed to guide the planning process. Accessibility metrics discussed in this paper include types of nature, size of green space, and distance.

Types of nature include urban parks, countryside, blue space (water) and small natural areas (public and private). Within each of these types, there are also sub-types. Both domestic gardens and street trees, for example, are sub-types of small natural areas. In addition to types of nature, there are different types of engagement or involvement with nature. Engagement can vary from viewing nature from a window to being actively engaged with nature through a hands-on activity such as gardening.

The question of size of green space is also raised as an accessibility-metric issue. Is there a minimum size required for a green area to have an effect on health and well-being? While many studies report an association between urban green space and health, most do not quantify size of green space. From these studies, a quantifiable cut-off point can’t be determined. Studies have also reported on distance as influencing the frequency of use of green space, with increasing distance being associated with decreased use.

This review includes a comparison of residential proximity accessibility metrics with cumulative opportunity metrics indicators (considering all the green space within a certain distance). A conclusion drawn by the authors is that a residential proximity indicator may not be the best choice in analyzing the impact of nature on human health and well-being. Cumulative opportunity indicators, they suggest, tend to show better results. Several reasons are offered for this, including different types of green areas offering different types of engagement possibilities and appealing to different interests.

Their recommendations for further research include comparing different types of accessibility metrics and, at the very least, describing in full detail the accessibility metric that is used. Considering the question “How precisely does contact with nature impact health and what type and qualities are relevant in this regard?” will, they suggest, lead to more evidence-based accessibility metrics that will advance the field of landscape and urban planning.