It’s well accepted that time spent in nature is good for mental and physical health. In cities, living in a neighborhood with parks helps to reduce air pollution, improve moods, and keep residents fit. While green spaces should be encouraged in whatever form possible, they’re not all created equal. One surprising finding is that just size and location, but also shape, matters when it comes to parks’ effects on human health.
In November, The Lancet Planetary Health published an intriguing study by Huaqing Wang and Louis G Tassinary on how the shape of greenspace in a Philadelphia neighborhood relates to mortality reduction. This was based on landcover images, census tract data on causes of death, and residence in a neighborhood with green spaces bigger than 900 square feet.
The researchers found that size isn’t the only important influence on health, although size does matter. Coauthor Wang studied landscape architecture in China and now combines this with urban planning research as a PhD researcher at Texas A&M University. Wang puts the effects into perspective, giving the example of a community with 100,000 residents and an average of 878 deaths per year. “In this kind of community, a 1% increase in the percentage of greenspace is expected to reduce 3.67 deaths per year,” Wang explains.
Surprisingly, squigglier parks benefit health as well. Connected, clustered, and irregularly shaped green spaces also significantly (though modestly) reduce mortality rates.
There are several possible reasons:
– large and linear parks are more appealing to walk and cycle in than compact ones
– residents are more likely to stumble across parks that have odd shapes and many entry points compared to perfectly geometric ones
– the urban microclimate is more varied, and potentially less prone to air pollution, when green spaces sprawl
Fairmount Park in Philadelphia. (Photo by Bastiaan Slabbers)
NurPhoto via Getty Images
More research is needed to tease out the effects. The Philadelphia study is a neighborhood-level analysis, not one that looks at the city as a whole. It would be interesting to see how different kinds of neighborhood, with different demographic and spatial patterns, are affected by the shape of greenspace.
The authors chose Philadelphia because of the availability of highly specific data, but this research has since expanded to other cities in the US, including both major metropolises and smaller cities. Wang says that the results are consistent: parks with more complex shapes are associated not just with lower mortality rates, but also lower prevalence of certain chronic diseases.
Wang’s primary recommendation for planners and landscape architects is straightforward: “Keep greenspace as connected as possible.” This could involve, for instance, linking small and fragmented parks with greenways, or natural corridors.
She also suggests embracing complex shapes. In a residential area, for example, “a small number of larger parks will be much better than many small lawn parcels.” Tiny pocket parks, while delightful, just don’t offer the same opportunities for recreation and exercise.
Of course, there are practical obstacles to rejigging the layout of parks. For one thing, there may be security concerns or staffing costs involved with adding lots of entrances. But Wang’s suggestions aren’t inherently expensive.
The best park is a park that many people use. But when it comes to designing urban parks, perfect symmetry may not be the best way to go.