12/10/2015 05:27 pm ET Updated Dec 06, 2017

Which Aspects of Nature Improve Our Health?

Landscape attributes / MaryCarol Hunter

"We know that exposure to nature enhances our well-being, but we know less about the specific features that create these positive effects," said MaryCarol Hunter, ASLA, University of Michigan, at the ASLA 2015 Annual Meeting in Chicago. A set of fascinating studies by Hunter and Marc Berman, a psychologist and neuroscientist at the University of Chicago, are beginning to converge on what those feature are. The goal is to translate knowledge of these features into design guidelines landscape architects and other designers can apply. All of this research is happening under the rubric of the TKF Foundation, which has invested millions over the past two decades creating more than 130 small, healing parks and financing research studies on the health benefits of green spaces in dense, urban areas. The TKF Foundation wants to know: with increasingly limited space in cities for green space, how can we have the biggest impact?

Humans evolved in wild lands, but we mostly live in urban environments now. While we inherently connect with our ancestral landscapes, we are constantly exposed to cacophonous city life. Wild landscapes can't be fully translated into urban environments, but "some elements can be transported to downtowns. We can get close to the effects of wild places," said Hunter.

Exposure to Nature Improves Our Sense of Well-being and Ability to Focus

First, we should look at some of the research Hunter and Berman are conducting to demonstrate the health benefits of nature. Hunter and her collaborators from many fields created a mobile-phone app that study subjects used to record their responses to nature and also photograph scenes of nature they connected with. This experiment is detailed in an earlier post, but the key finding so far is that just a 10 minute exposure to nature 2-3 times per week was "sufficient to produce restoration benefits." Furthermore, subjects were most likely to experience the effect of this "nature pill" in a small urban park or residential yard instead of a large park. The findings from those using the app were confirmed by cortisol and saliva samples taken to measure the physiological effects of stress.

Marc Berman then described his own research at the University of Chicago. In one experiment, a set of subjects were asked to take a 2.5 mile walk, which took about 50 minutes, through a dense urban environment, and another set were asked to take another 2.5 mile walk through an arboretum. Subjects taking either path converged on a lab at the University of Chicago where they were put through the stressful "backward digit span" test of working memory, which Berman uses to measure capacity to concentrate or focus. The test involves reciting back a set of numbers in reverse. As number strings become longer, it becomes more mentally taxing to recite them backwards. Berman found that subjects who walked through the arboretum had a 20 percent improvement in working memory. A further study that showed subjects either photos of urban areas or nature scenes had a similar effect.

Elements of Nature that Boost Health Benefits

Hunter and Berman both seek to zoom in on the specific elements of nature that create a sense of well-being and improve the ability to concentrate. But there are so many outstanding questions. Just consider the question: "why do trees have a beneficial effect?" Berman said possible answers could be: "they make places beautiful so we want to go out and exercise; they clean the air; they help us reach resting attention rates; or perhaps all of the above." Now think of all the other elements of nature that need to be isolated and considered.

Still, Berman suspects that the effect of nature has something to do with the "soft fascination" it creates for us. "Nature captures our attention but not all of our attention. We can watch a waterfall, but our minds can wander and we can think about other things. In contrast, in Times Square, New York City, our minds can't wander. There, we can't daydream."

Berman is creating a taxonomy of natural and urban image elements, coding them by brightness and color value, saturation, hue, and then calculating the standard deviation of these elements. He's also analyzing the images' "grey scale entropy," removing all the color and just looking at the complexity of the content in the images. He said that "images of nature are more complex and therefore have a higher grey scale entropy." He's also evaluating images based on whether they have curved or straight edges. "Color, structure, and their interactions all matter." Running all this data through an algorithm, Berman says he can predict "how natural we think a scene is. These preferences can be measured with 80-90 percent accuracy."

Berman's algorithm tells him that color has less of an effect on our perceptions of naturalness than whether there are straight or hard edges. This means that designers of all kinds can "mimic the edge-making of nature" and have some beneficial effect.

Hunter is doing her own taxonomy, too, because her goal is to "bring science into landscape architecture." She is pulling the physical landscape attributes out of the photographs collected through her app study, categorizing them based on "naturalness, complexity, structural coherence, form, proportion, openness, access, safety, and engagement."

While her analysis is ongoing and the full design guidelines aren't ready yet, Hunter found through her research that "vibrancy" is something to maximize whenever possible. She defined vibrancy as "the interaction between the sky and the surface water or waxes of foliage, which creates a sparkle effect that engenders soft fascination."

Maximizing vibrancy / MaryCarol Hunter

And framing -- in which an object near the viewer partially obscures and also reveals what's beyond -- also creates a sense of safety and continuity and is a design element that should be incorporated in landscape architecture.

Example of framing / MaryCarol Hunter

The Long View

But these are really just starting points, as the full design guidelines are still forthcoming. And Hunter said there are many others also involved in this research, with some looking at the role sound plays in the health benefits of nature. An audience member wondered when they would look at tactile elements of nature and smell. Hunter said they were starting first with visual components but the goal is to broaden the reach to other senses.

Jay Graham, FASLA, Graham Landscape Architecture, and long-time adviser to the TKF Foundation, said their efforts will show how "scientific research can lead to more successful sanctuaries." All the research -- which also includes a study by Roger Ulrich of a healing garden created by Brian Bainnson, ASLA, at Legacy Emanuel Hospital in Portland, and another of a healing pathway by Jack Sullivan, FASLA, University of Maryland at Walter Reed Army Medical Center in Washington, D.C. -- is due in 2018. Then, the TKF Foundation will promote these findings to the media, policymakers, and the broader public.

As Graham explained, the TKF Foundation seeks to educate the public about why small urban green spaces are important, because according to their internal research, "the public doesn't comprehend the health benefits of nature." Landscape architects then play a leading role, given they "bring nature into cities, and create spaces that show people the transformational effects." The idea is if lots more of these evidence-based urban green spaces are created and the benefits of them are made clear through research, the public will demand even more of them.