A cable ski lagoon in Singapore, May 6, 2014. Wong Maye-E / AP

What does it mean for public health officials?

The connection between green space and human well-being is so intuitive as to seem axiomatic. Cities abound with stressors, countless studies suggest, and contact with natural environments can help residents take the edge off.

But according to a recent study published in PLOS ONE, it’s not as simple as “nature makes people happy.”

Scientists at the National University of Singapore surveyed students across the island state to determine the relationship between their use of natural parks and their self-reported well-being.

The respondents were asked for background information including age, income, physical activity, personality traits (extraversion and neuroticism), and emotional stability. They also provided their postal codes, allowing researchers to map their proximity to four types of green spaces: protected nature reserves, regional parks, neighborhood parks, and park connectors. Respondents rated their subjective life satisfaction and their positive and negative affect (measures of emotional state). Stress was measured on a separate scale.

Ultimately, the researchers found that neither access to nor use of Singapore’s green spaces had a significant impact on the respondents’ well-being. The most significant influence on well-being, in fact, was the underlying emotional stability and personality of the respondent. Stable, extraverted people tend to feel happier—and this doesn’t necessarily have anything to do with nature.

These results fly in the face of numerous studies extolling the benefits of green space on human health. And while the research in Singapore doesn’t invalidate those claims, it does complicate the conventional wisdom—especially as it applies to tropical cities.

Gardens by the Bay in Singapore, March 6, 2014. (Edgar Su / Reuters)

Different climates, different outcomes

The Singapore study highlights the geographical limits of previous research in this realm. Many studies that linked contact with nature to well-being focused on temperate regions such as the U.K. and the U.S., where greenery can mitigate the urban heat island effect.

That’s true in Singapore, too, but because of the city-state’s perpetually hot and humid climate, people typically head indoors for air-conditioned relief. The study’s authors write that this behavior could be “subverting the cooling benefits that green spaces offer” and that “climatic differences may explain the variation in the quality of one’s experience when using urban green spaces within different parts of the world.” In other words, Singaporeans may derive less enjoyment from the outdoors than their European counterparts—simply because it’s so damn hot outside.

Green, green everywhere

On the other hand, it could be the very ubiquity of green spaces in Singapore that makes their effect on well-being difficult to detect on a citywide scale. Singapore is one of the greenest cities in the world, with parks and gardens occupying 47 percent of all land. (Compare that to 14 percent public green space in New York and 29 percent in Rio de Janeiro.) Because green space is everywhere, the authors write, “people may easily feel refreshed and restored by the surrounding greenery without the need to be sited within a green space with predefined boundaries.” Singaporeans may see so much plant and animal life that they take it for granted, such that the health benefit of natural environments is imperceptible on the city level. It’s the law of diminishing returns, for green spaces.

Policy implications

Far from obviating the need for urban greenery, however, this study opens the door to future inquiries into the benefits of a holistic approach to green space. Singapore’s lushness is no accident; it has been a cornerstone of public policy from prime minister Lee Kuan Yew’s “Garden City” movement of the 1960s to the enlarged “City in a Garden” vision of today. Through tree planting, wildlife conservation, park construction, and other green initiatives, Singapore has worked to create a modern metropolis intertwined with the natural world. And it’s worth exploring whether other cities ought to strive for Singapore’s overwhelming verdancy, in the interest of public health.

Researcher Luis Roman Carrasco is careful to note that the study raises more questions than it answers. “We need to think carefully of future temperatures in the light of climate change with regards to thermal comfort, especially in the tropics,” he said in an email. “Design should consider air circulation and use plants to reduce heat. We have also to think how people move in the city and consider ways to bring nature to those that do not go to parks, looking at commuting routes and working places, for example.”

But perhaps the most important takeaway is also the most basic: We need to look beyond the Western world to understand the effects of green space on health and well-being.

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