The Benefits of Green Spaces

In 2012, a group of backpackers embarked on a multi-day journey into the wilderness, leaving behind phones and electronics. Before their adventure, they took a creativity and problem-solving test. After four days in nature, their scores improved by 50%, rising from an average of 4.14 correct answers out of 10 to 6.08.

As with many psychological studies, this one could not definitively establish cause and effect. It could not ascertain whether the nature experience itself, the disconnection from technology, or the physical activity contributed to the improvement. However, the researchers from the University of Kansas and the University of Utah shared their intuition:

“Our modern society is inundated with abrupt stimuli (sirens, horns, ringing phones, alarms, television, etc.) that disrupt our attention,” they wrote in PLOS ONE. “Conversely, natural settings are associated with gentle, soft fascination, allowing the executive attentional system to rejuvenate.”

“Spending time in, or living near, natural green spaces is linked to diverse and significant health benefits.”

Prior studies have demonstrated that the advantages of green spaces are not limited to seasoned adventurers like Marlin Perkins or Bear Grylls. Even small patches of greenery can make a difference.

In 2006, research led by behavioral scientist Jolanda Maas at Vrije University Amsterdam found that the amount of green space within a two-mile radius significantly correlated with perceived overall health. This conclusion stemmed from actual greenery measurements compared to questionnaire responses from 250,782 individuals in the Netherlands.

Maas and her team conducted another study in 2009, analyzing morbidity data. Of the 24 diseases examined, the incidence of 15 was lower among individuals residing in greener areas, with the strongest links found for anxiety disorders and depression, as reported in the Journal of Epidemiology & Community Health.

Further studies have shown that views of gardens and access to green spaces can alleviate stress and pain in hospital patients, enhancing immune function and facilitating recovery.

Interestingly, a small study in 2011 revealed that gardening reduced stress more effectively than reading. In this experiment, 30 participants performed a stressful task, then either gardened outdoors or read indoors for 30 minutes. The researchers measured cortisol levels, a stress hormone, and assessed mood before and after.

“Both gardening and reading led to reductions in cortisol during recovery, but the decrease was significantly more pronounced in the gardening group,” the scientists noted in the Journal of Health Psychology. “Positive mood returned completely after gardening, whereas it further declined during reading.”

A comprehensive review last year, involving data from over 290 million individuals across 20 countries, highlighted the physical health benefits of nature.

Lead author Caoimhe Twohig-Bennett from the University of East Anglia stated, “We found that time spent in, or living near, natural green spaces is associated with a variety of significant health benefits,” including decreased risks of type II diabetes, cardiovascular diseases, early mortality, and preterm births, as well as improved sleep quality. Those living closer to nature also exhibited lower diastolic blood pressure, heart rate, and stress levels, as indicated by cortisol measurements.

The Role of Physical Activity

An important caveat in many of these studies is that being outdoors often involves physical activity.

Whether hiking, gardening, or simply walking briskly in a park, participants in these studies may be engaging in what scientists refer to as “moderate physical activity,” which is known to enhance mood, improve cognitive function, support physical health, and increase longevity.

“Individuals living near green spaces likely have more chances for physical activity and social interactions,” Twohig-Bennett acknowledged, emphasizing the challenge of establishing cause-and-effect relationships.

Research remains inconclusive regarding whether it’s the natural environment itself or the physical activity associated with it that yields health benefits. Douglas Becker, a graduate student at the University of Illinois, recently published a study on nature's impact on healthcare costs.

Becker analyzed health and environmental data from nearly all 3,103 counties in the continental U.S. He discovered that counties with more forests and shrublands incurred lower Medicare costs per capita. Notably, each 1% increase in forest cover in a county correlated with an average savings of $4.32 per person annually.

Becker performed additional calculations, which suggested that if multiplied by the number of Medicare beneficiaries in a county and the average forest coverage, the total savings could reach approximately $6 billion in reduced Medicare expenditures nationwide each year.

So, is the solution to plant more trees? While Becker's analysis, set to be detailed in the May 2019 issue of Urban Forestry and Urban Greening, does not establish a direct link between increased tree cover and lower healthcare costs, it adds to the evidence supporting the health benefits of green spaces, particularly forests.

“Being near nature indeed provides advantages,” he stated.

Twohig-Bennett introduced another potential factor from her literature review, suggesting that exposure to diverse bacteria present in natural areas might boost immune function and reduce inflammation. She noted that studies have indicated potential benefits from “forest bathing,” a popular therapeutic practice in Japan that involves immersing oneself in nature.

“Much of the research from Japan suggests that phytoncides—organic compounds with antibacterial properties released by trees—could explain the health-enhancing effects of forest bathing,” Twohig-Bennett remarked. While research on this therapy is ongoing, “our findings indicate they might be onto something,” she added.

The Psychological Impact of Nature

In 2015, Stanford University researchers contributed to the growing body of evidence highlighting the unique benefits of nature itself, beyond just the physical activity involved in reaching it. They studied the effects of hiking in a natural environment (oak trees and shrubs) versus an urban setting (along a busy roadway). Participants were surveyed before and after their hikes, and their heart rates, respiration, and brain activity were monitored.

The study, published in the Proceedings of the National Academy of Sciences, found no significant physiological differences between the two groups post-hike. However, those who hiked in natural settings exhibited decreased activity in the subgenual prefrontal cortex, the brain region associated with persistent negative thoughts. Reduced activity in this area is considered beneficial.

“This demonstrates how experiencing nature influences emotion regulation—providing insight into how nature contributes to our well-being,” stated lead author Gregory Bratman, then a graduate student.

Bratman’s co-author, Stanford psychology professor James Gross, highlighted the implications of these findings:

“These results are significant as they align with, yet do not definitively prove, a causal relationship between urbanization and rising mental health issues.”

Furthermore, early immersion in nature seems beneficial.

A study involving nearly one million Danes revealed that growing up in greener environments is linked to up to a 55% lower risk of mental health disorders in adulthood. Kristine Engemann of Aarhus University, who led the study, stated, “Our research indicates that the natural environment significantly influences mental health more than previously recognized. Our data shows that the risk of developing mental disorders decreases incrementally the longer one is surrounded by green spaces from birth to age 10.”

Educators have long acknowledged the positive impact of nature on children’s well-being. As scientific support for this premise grows, the number of nature-based preschools and “forest kindergartens” in the U.S. has surged by over 60% in recent years, allowing more children to experience education largely outdoors.

The Nature Prescription

How much time is necessary in nature to experience these benefits? While the consensus suggests that more time is advantageous, recent findings indicate that even brief encounters can be effective.

A study published on April 4, 2019, in Frontiers in Psychology revealed that spending just 20-30 minutes in a natural setting can lower cortisol levels, the stress hormone. Researchers had 36 urban residents take breaks of 10 minutes or longer, three times a week over eight weeks, in locations that felt natural to them. Participants were instructed to avoid aerobic exercise, reading, talking, and using their phones during these breaks.

The study concluded that the most significant stress-reducing effects occurred among those who spent 20 to 30 minutes in nature.

“While it’s known that time in nature alleviates stress, the optimal duration, frequency, and nature experiences for benefits have been unclear,” stated lead author MaryCarol Hunter from the University of Michigan. “Our study indicates that for maximum stress reduction, spending 20 to 30 minutes in a natural setting is ideal.”

Hunter and her colleagues propose that healthcare providers could prescribe a “nature pill” based on these findings.

Coupled with regular exercise, sufficient sleep, and a balanced diet, a “nature pill” could serve as a cornerstone of science-backed well-being strategies. For my son and me, visiting our favorite fishing spot daily isn’t feasible. However, there’s a hiking trail near our home leading into the desert and up a mountain. We’ll make sure to explore it.