What Dose of Nature Do We Need to Feel Better?

06/24/2015 10:19 pm ET | Updated Jun 24, 2016


Central Park, New York City / Drive the District

There has been a boom in studies demonstrating the health benefits of spending time in nature, or even just looking at nature. But a group of ambitious landscape architects and psychologists are actually trying to determine how to prescribe a "nature pill." The big remaining questions are: What dose of nature exposure is needed to achieve maximum mental and physical health benefits (how long and how frequently)? And what form of nature works best? In a talk at the Environmental Design Research Association (EDRA) conference in Los Angeles, MaryCarol Hunter, a landscape architect and ecologist at the University of Michigan, described her efforts to create the guidelines for landscape designs that can lead to the greatest impact.

Hunter and her team examined 44 people over 8 weeks. She asked them to go out and immerse themselves in urban natural environments at least 2.5 times per week for a minimum of 10 minutes. Using a custom-designed smartphone app, these people walked or sat in nature and then answered questions about their mental well-being, both before being exposed to nature and then after. They were asked to record the types of landscapes they saw, the weather, and then take photographs of their preferred views, "scenes they were drawn to, that gave them that 'ahhhh' feeling." As the walked and recorded their thoughts, the app also tracked their location.

The early results show that the "nature pill works." Among all participants, they reported significantly less stress, an increased ability to focus, and increased satisfaction with their mood and energy levels after being exposed to nature. But Hunter admitted that "self-reported data is viewed as worthless; people want physical proof," so before and after the nature exposure, they also studied participants' cortisol levels, a physical indicator of stress, which correlated with the self-reported responses more than 60 percent of the time. She said this shows the data is largely credible.

Hunter said it's still too soon to tell what the optimal dose of the nature pill is, but even just "10 minutes is effective." While the data is still being analyzed, Hunter and her colleagues also found that "there was no correlation between weather and the restorative effects." There were greater restorative effects in residential landscapes or small parks. In fact, the benefits seemed to be greater in "small, enclosed spaces," but this could also be a function of how the participants' neighborhoods were set-up. It's not clear whether large parks were actually nearby those studied.

The definition of nature was loose, so, in the next stages of the research, Hunter is trying to define it more specifically. For example, vegetation, hills, rivers, or large bodies of water can all be considered nature, so she began a process of listing all the physical attributes defining the environment to find out which have the most restorative benefits. She categorized the 470 photographs study participants took through the app with 60 attributes, covering factors like naturalness, complexity, structural coherence, form, proportion, openness, access, and engagement. There were some 23 structural attributes, like "horizontal line, skyline, or canyon form," 13 contextual attributes, and another 30 landscape attributes.

Now that there are a set of photographs with clear attributes, Hunter can begin testing theories. For example, Roger Ulrich, who is perhaps the most celebrated health and nature researcher, posited that symmetries, repeated elements, and focal points helped stress recovery more than other forms. Using the categorized photographs, she can begin to see whether this is true.

Hunter hopes to have her exciting findings ready to present at the ASLA Annual Meeting in Chicago in November. "We are still working on deciphering the nature pill." Her eventual goal is to create a methodology that can be replicated all over the world, given other cultures have such a different appreciation of nature. "Other researchers can use the procedure but adapt specifics."

Here are brief summaries of other fascinating health and nature studies at EDRA:

Dongying Li, a landscape architecture PhD student at the University of Illinois at Urbana-Champaign, examined whether exposure to nature for high school students improved their ability to deal with stress. She tracked 150 high school students in Illinois with GPS devices and asked them to keep an active diary each night. Li also collected various mood-related data every day. In her exploration of a new "time/space model," she found that simply estimating the level of use of green spaces in an area based on proximity to those spaces doesn't really work. Students with three-hour windows of opportunity who could have accessed green spaces often didn't in reality. "Potential versus realized exposure can be different." For Li, the take-home message was "design green spaces that are walking distance. Parks in neighborhoods may not be enough." William Sullivan, professor of landscape architecture at the University of Illinois at Urbana-Champaign, who is doing much of the exciting research on nature and health, added that "nature needs to be at every doorstep. We don't know where people will wander."

Jane Buxton, a PhD student in regional planning at University of Massachusetts at Amherst, conducted a novel study to find out whether increased tree canopy influences people's preferences for urban density. She found that "trees will help people accept density." Buxton showed 24 photographs, some of which were manipulated to incorporate more trees, to 70 residents of Worcester, Massachusetts, the second largest city in New England, asking them to circle the choices that "best describe where you want to live." The highest preference was for single-family homes set in a rich tree canopy; the lowest preference was for apartments close to street with a lack of trees. Greening made a difference. In almost all cases, the scores went up as more trees were added. She concluded that "there is a tension between higher density and what people actually want: single-family homes. Trees can ameliorate that tension up to a point." She also believes that "people will need to chose higher density if it's going to work. It can't be seen as something that will be forced on people."

Pongsakorn "Tum" Suppakitpaisarn, a PhD student in landscape architecture at the University of Illinois at Urbana-Champaign, and Bin Jiang, a professor at the University of Hong Kong, want to figure out if people's preferred landscapes reduce stress. Preference, as defined, is "spontaneous, aesthetic," but also about survival. Suppakitpaisarn showed slides of a winding open path in a park versus a dark hallway through a crumbling building, explaining how most everyone will prefer the open path, because it appears less dangerous. There's a reason for that preference: it's about survival. Through a set of studies, he stressed people out by asking them do math and perform in a job interview in front of unresponsive, unhelpful people and then asked them to watch nature videos and rank their preferences for the green scenes, which aided in stress recovery. He found that preference predicts stress recovery in women but "we're not sure about men." Why should we care? "Stress is expensive to measure, with all the physiological measurement equipment, but preference is easy to measure."

Sara Hadavi, a research associate at the University of Michigan, looked at various types of green spaces in 3,400 acres of Chicago. Using mail-in surveys and on-the-street-interviews, she got 434 people to respond to her questions about nearby nature and well-being. Hadavi found that "open lawns with trees had a positive effect on well-being, even if they aren't used. Just knowing that they are there is enough to inspire satisfaction with public spaces, which in turn improves well-being." She said this kind of information is important for planners and landscape architects who may think the only measure of success for a public space is direct use. But she added if city leaders really want to boost well-being, landscape architects should create spaces where people can socialize and then encourage them to visit through lots of programs. Hadavi called for more widespread use of "user-oriented design, which will have better outcomes than designer-oriented design."

Eva Silveirinha de Oliveira, a landscape architect and researcher at Open Space in Scotland, is testing out a new environmental audit tool on woodlands. "Urban woodlands are part of green infrastructure systems, but their quality varies. They are not usually managed or maintained in Scotland." Sending out two trained landscape architects, she completed 18 audits, and found the tool works in helping us to "get a sense of whether a place will attract or repel us." She said the views of the urban woodlands among the landscape architects and the locals she surveyed who live near them were different though. "Landscape architects recorded much lower ratings than the community." Like Hadavi, Silveirinha de Oliveira found that people valued nearby nature even if they didn't use it.