[in] individuals’ self-report but also [in] measures of pulse rate, blood pressure, and stress-related patterns of nervous system and endocrine system anxiety, as well as physician-diagnosed anxiety disorders,” wrote Frances Kuo, director of the Landscape and Human Health Laboratory at the University of Illinois at Urbana-Champaign, in a research report for the National Association of Parks and Recreation.
One study by Kuo even showed that greenery has enough of a calming effect to reduce crime. At one Chicago public housing development, there were significantly fewer crime incidents in and around buildings surrounded by trees and greenery than in a nearby identical building surrounded by barren land.
Some researchers are exploring how to make forests even more healthful. Researchers at the Finnish Forest Research Institute created a well-being-themed forest trail. To help hikers get the most from their walk, signposts offer suggestions such as: “Listen to one of the voices of nature, the changes in the soundscape or the silence. … Youmay squat down and feel a plant, a rock, or the surface of a tree. Feel yourmood improve.”
“According to our questionnaire, a majority of the visitors felt that the trail enhanced their restorative experience and improved their mood,” says Tytti Sarjala, senior researcher at the institute.
Though the potential for preventive medicine is huge, the relationship between health and forests is often downplayed or ignored. Godbey suggests that since healthcare is among the largest expenditures by Americans, there’s an untapped health asset in forests that has tangible economic value, “but the case hasn’t been made yet.”
SOMETHING IN THE AIR
In Japan, researchers are finding strongmedical connections between being in a forest and having a healthy immune system. In one Japanese tradition — shinrinyoku, or forest bathing — individuals spend time in a forest to relieve stress and strengthen their immune system.
According to Yoshifumi Miyazaki, a professor at the Center for Environment, Health, and Field Sciences at Chiba National University in Japan, forest bathing has “preventive medical effects” such as relieving stress and recovering an immune system that has declined due to stress. He adds, “Artificialization is taking place at such a rapid rate that we now find ourselves in stressful situations in our daily lives and are forced to deal with the resultant pressure.” Proponents of forest bathing assert that a short trip to a forest offers relaxation as well as natural aromatherapy in the form of antimicrobial organic compounds derived from trees: woodessential oils called phytoncides.
A man runs on a trail through old-growth forest in Mt. Hood Wilderness Area, Oregon. Credit: Danny Warren/iStockphoto
In 2009, Qing Li from Nippon Medical School in Tokyo published a paper highlighting a series of studies that followed groups who took a threeday/ two-night trip to forested areas. Researchers took blood and urine samples at various intervals. Li found that an individual’s levels of natural killer cells — a type of white blood cell that releases anticancer proteins to attack tumors and cells infected by viruses — were significantly higher on the forest bathing days. Moreover, natural killer-cell levels stayed elevated for 30 days after the trip. In addition, Li found that levels of urine adrenaline, which the body releases in response to anxiety, had dropped after forest bathing trips — a sign that forests lower stress.
Li’s findings suggest a monthly “forest bathing trip” would help people maintain a higher level of natural killer-cell activity. “Forest bathing trips have become a popular and recognized relaxation and stress management activity in Japan,” says Li.
Though the forests in Li’s research held Japanese cypress, Japanese cedar, and Japanese beech, he said that other types of forests should have similar effects, though researchers haven’t yet studied other tree species’ phytoncides.
In a similar 2005 study in Japan, Miyazaki and colleagues conducted week-long studies in 44 different forest sites throughout Japan. In one study, groups took a seat in the forest to absorb natural surroundings, while an urban-based control group viewed city life. Researchers found the forest group to have decreases in cortisol (stress hormone) levels, sympathetic nervous activity, blood pressure, and heart rate; parasympathetic nervous activity was enhanced by 55 percent, indicating a relaxed biological system.
“This proves that stressful states can be relieved by forest therapy,” Miyazaki says.
A RENEWED MIND
“Just being around living green things has an effect mentally and emotionally,” says Linda Kruger, who takes advantage of the numerous trails near Juneau.
A number of studies have examined the effects of natural settings on children with attention deficit disorders and found that spending time in green areas helps calm their symptoms. In one, seven- to 11-year-olds with ADHD showed improved concentration after taking a 20-minute guided walk in a park, as opposed to 20-minute walks in a downtown area or an urban park. “A lot of times, kids will respond to being out in nature and will do better in school if they have ‘green breaks’ — a chance to walk through the forest during the day,” says Kruger. “It helps them to have better mental functioning during the school day.”
Many people accustomed to encountering forests and green spaces on a regular basis feel a subconscious yearning to get outdoors. Says Kruger, “When I don’t get out, I get restless, and mentally, I don’t function as well; physically and mentally, I feel better if I can spend time out in the forest every day or two.”
Carrie Madren writes from Olney, Maryland, and can be reached at firstname.lastname@example.org.