TIME SPENT IN the natural world can help build our physical, emotional, and family fitness. The mind/body connection, of course, is a familiar concept, but research and common sense suggest a new container: the mind/body/nature connection.
Over two thousand years ago, Chinese Taoists created gardens and greenhouses to improve human health. In 1699, the book English Gardener advised the reader to spend “spare time in the garden, either digging, setting out, or weeding; there is no better way to preserve your health.” And a century ago, John Muir observed that: “Thousands of tired, nerve-shaken, over-civilized people are beginning to find out that going to the mountains is going home; that wilderness is a necessity; and that mountain parks and reservations are useful not only as fountains of timber and irrigating rivers, but as fountains of life.”1
Today, the long-held belief that nature has a direct positive impact on human health is making the transition from theory to evidence and from evidence to action. Certain findings have become so convincing that some mainstream health care providers and organizations have begun to promote nature therapy for an array of illnesses and for disease prevention. And many of us, without having a name for it, are using the nature tonic. We are, in essence, self-medicating with an inexpensive and unusually convenient drug substitute. Let’s call it vitamin N—for Nature.2
New research supports the contention that nature therapy helps control pain and negative stress; and for people with heart disease,3 dementia,4 and other health issues, the nature prescription has benefits that may go beyond the predictable results of outdoor exercise.5 The restorative power of the natural world can help us heal, even at a relative distance. On the surgical floors of a two-hundred-bed suburban Pennsylvania hospital, some rooms faced a stand of deciduous trees, while others faced a brown brick wall. Researchers found that, compared to patients with brick views, patients in rooms with tree views had shorter hospitalizations (on average, by almost one full day), less need for pain medications, and fewer negative comments in the nurses’ notes.6 In another study, patients undergoing bronchoscopy (a procedure that involves inserting a fiber-optic tube into the lungs) were randomly assigned to receive either sedation, or sedation plus nature contact—in this case, a mural of a mountain stream in a spring meadow and a continuous tape of complementary nature sounds (e.g., water in a stream or birds chirping). The patients with nature contact had substantially better pain control.7
Nearby nature can be an antidote to obesity. A 2008 study published in American Journal of Preventive Medicine found that the greener the neighborhood, the lower the Body Mass Index of children. “Our new study of over 3,800 inner city children revealed that living in areas with green space has a long term positive impact on children’s weight and thus health,” according to senior author Gilbert C. Liu, MD. While the investigation didn’t prove a direct cause-and-effect, it did control for many variables, including the neighborhood’s population density. The results support those who believe that changing the built environment for inner-city kids is just as important as attempts to change family behavior.8
While it’s true that too much exposure to sunshine can lead to melanoma, too little time outside can also have a negative health impact. According to one study, as many as three-quarters of U.S. teens and adults are deficient in vitamin D, which is obtained naturally from sunshine and some foods, or supplements. African Americans are especially at risk, one researcher explains in Scientific American, because “they have more melanin or pigment in their skin that makes it harder for the body to absorb and use the sun’s ultraviolet rays to synthesize vitamin D.”9 Some scientists question the percentage of people who may be at risk (which may be closer to half than three-quarters), but there is agreement that vitamin D blood levels are dropping and that deficiency is associated with a large number of health problems, including cancers, arterial stiffness in African American teens, type 2 diabetes, lower mood levels during winter, decreased physical strength in young people, and decreased lung function for children with asthma. Vitamin D also has been found beneficial in reducing risk for some infectious diseases, autoimmune diseases, fractures, and periodontal disease.
More research has been conducted on the impact of nature time on mental health than on physical health; the two arenas (along with mental acuity) are interrelated. The science isn’t all in, and available evidence is not entirely consistent. Much of it is correlative, not causal. However, an honest reading of the science can yield cautious conclusions.
Several reports, including a thorough literature review by researchers at Deakin University in Melbourne, Australia, chart what is known.10 According to the Deakin review, each of the following health benefits, among others, is supported by anecdotal, theoretical, and empirical research:
• Exposure to natural environments, such as parks, enhances the ability to cope with and recover from stress and recover from illness and injury.11
• Established methods of nature-based therapy (including wilderness, horticultural, and animal-assisted therapy) have success healing patients who previously had not responded to treatment of some emotional or physical ailments.12
• People have a more positive outlook on life and higher life satisfaction when in proximity to nature, particularly in urban areas.13
In 2007, naturalist Robby Astrove and I were driving through West Palm Beach, Florida, on our way to an event promoting the preservation of the Everglades. He told me: “As a kid, I was always glued to the car window, taking notice. I still do this and must sit in a window seat when flying. Looking back, it’s no wonder I’m a naturalist, having trained my senses to detail, patterns, images, sounds, and feelings.” In fifth grade, a school field trip to the Everglades led to his career choice. After college, he surveyed hundreds of miles of the Everglades. As an educator, he has taken thousands of students to the Everglades, to learn about the great river of grass, the threats to it, and its recovery. In 1979, when he was fifteen, Astrove was diagnosed with HIV and hepatitis C, which he contracted from three life-saving blood transfusions for a staph infection that had spread from a blister on his thumb. Following the blood test that revealed HIV, he was called into the doctor’s office. He found his parents in tears. “The doc sat me down and shared the news. My first words were, ‘What are we going to do now?’”
During the ensuing years, he found himself drawn, more and more, to the river of grass. “It’s hard to explain, but acknowledging the cycles, patterns, and interconnectedness of the world has provided healing to me,” he said. “Sometimes I awake in the middle of the night and find myself putting on boots, grabbing a raincoat and collection containers. I don’t question actions like that. I’m excited to hike in the dark not knowing what I’ll find. It might not be until I hear the call of a barred owl that I realize why I came. Or seeing a familiar tree that I’ve studied a million times during the day that reveals something new at night. I go because I trust my instincts, have patience, and allow for things to happen. Well, there’s luck, too. But the same trust and instinct is required to manage a disease. When I haven’t gotten enough nature time, my body tells me. I listen.”
Astrove, who is attending Emory University to study international public health, finds HIV biologically fascinating. “It’s able to reproduce rapidly and can mutate, always creating the demand for new medicines. In a weird way, HIV is elegant, beautiful. I understand what this monster is capable of, so I establish limits. Not staying out too late, eating healthy, not ever smoking.” Avoiding these behaviors as a teenager was difficult for him, but respect for the virus trumped peer pressure. “Nature is always making adaptations, so why can’t I do the same? I listen. When I hear ‘rest,’ I rest. When I see macroinvertebrates in a stream indicating clean water, that reminds me to pay attention to indicators for my own health. Stumbling upon a rare plant reminds me of the uniqueness of my situation. No two people are the same in their response to a virus.”
In his role as an educator, he teaches his students that wetlands serve as “nature’s liver” and relates to the system personally. “The wetlands purify water and trap pollutants.” He explains that the rain forests and other natural places are the source of many of our medicines, that spending time in that world reduces stress. “We feel good from the endorphin release it stimulates, and it inspires us. Inspiration is another giver of health. I go to the woods knowing I will receive healing. And the benefits come in the form of physical, psychological, and spiritual gains. It’s a natural high sometimes when I get the feeling of light, energy, and awe.” He looked out the truck window at the passing landscape as he drove. “Now that I’ve been taking meds for some time, sensitive blood tests can’t find the virus; I test ‘undetectable.’”
Does research give weight to Astrove’s experience? Possibly. A study of 260 people in twenty-four sites across Japan found that, among people who gazed on forest scenery for twenty minutes, the average concentration of salivary cortisol, a stress hormone, was 13.4 percent lower than that of people in urban settings.14 “Humans . . . lived in nature for 5 million years. We were made to fit a natural environment. . . . When we are exposed to nature, our bodies go back to how they should be,” explained Yoshifumi Miyazaki, who conducted the study that reported the salivary cortisol connection. Miyazaki is director of the Center for Environment Health and Field Sciences at Chiba University and Japan’s leading scholar on “forest medicine,” an accepted health care concept in Japan, where it is sometimes called “forest bathing.” In other research, Li Qing, a senior assistant professor of forest medicine at Nippon Medical School in Tokyo, found green exercise—physical movement in a natural setting—can increase the activity of natural killer (NK) cells. This effect can be maintained for as long as thirty days.15 “When NK activity increases, immune strength is enhanced, which boosts resistance against stress,” according to Li, who attributes the increase in NK activity partly to inhaling air containing phytoncides, antimicrobial essential wood oils given off by plants. Studies of this sort deserve closer scrutiny. For example, in the study of natural killer cells, there was no control group, so it is hard to say if the change was due to time off work, exercise, nature contact, or some combination of influences.
Nonetheless, for Astrove, wilderness has helped create a context for healing—and may have strengthened his immune system and offered protective properties that he, and the rest of us, do not yet fully understand.
Terry Hartig, currently professor of applied psychology at Sweden’s Uppsala University, offers a cautionary note. He sometimes gets the impression “that what the ‘nature’ people have in mind, when they talk about nature and health, is a ‘pasteurized’ nature —no teeth, claws, or stingers, offering no demands.” He also points out that by far the largest amount of research on nature and health concerns topics like infectious illnesses and natural catastrophes. “It’s important to bear in mind that people have been working hard over thousands of years to protect themselves from the forces of nature,” he says.
An important point. But here’s another view. From the backyard to the backcountry, nature comes in many forms. The negative impacts of the risks that do occur in wilderness (from large predators, for example) should be balanced by the positive psychological benefits of that risk (humility, for one). And, yes, most research on nature and human health has focused on pathology and natural disasters, but this preference by researchers has something to do with where the research funding comes from. Researchers looking at the health benefits of nature are, in fact, addressing a knowledge imbalance.
Relating to Hartig’s concern, science does have a difficult time defining how we perceive nature. A few years ago, I worked with a council of neuroscientists, experts on the childhood development of brain architecture. When asked how the natural world itself affects brain development, they would usually draw a blank. “How do you define nature?” they asked, rhetorically. However, these same scientists simulate “natural conditions” in their labs, for control groups. A friend of mine likes to say that nature is anything molecular, “including a guy drinking beer in a trailer park and a debutante drinking highballs in Manhattan.” Technically, he’s right. For the most part, we’ve left the definition of nature up to philosophers and poets. Gary Snyder, one of our finest contemporary poets, has written that we attach two meanings to the word, which comes from the Latin roots natura and nasci, both of which suggest birth.
Here’s my definition of nature: Human beings exist in nature anywhere they experience meaningful kinship with other species. By this description, a natural environment may be found in wilderness or in a city; while not required to be pristine, this nature is influenced at least as much by a modicum of wildness and weather as by developers, scientists, beer drinkers, or debutantes. We know this nature when we see it.
And centuries of human experience do suggest that the tonic is more than a placebo. How, then, when it comes to health does the nature prescription work?
The answers may be hidden in our mitochondria. As hypothesized by Harvard’s E. O. Wilson, biophilia16 is our “innately emotional affiliation to . . . other living organisms.”17 His interpreters extended that definition to include natural landscape. Several decades of research inspired by Wilson’s theory suggests that, at a level we do not fully understand, the human organism needs direct experience with nature.
Gordon H. Orians, a renowned ornithologist, behavioral ecologist, and professor emeritus in the Department of Biology at the University of Washington, maintains that our attraction to the natural environment exists at the level of our DNA, and, in its many genetic forms, haunts us. He points out that, between the first appearance of agriculture and this morning’s breakfast, only about ten thousand years have elapsed. “The biological world, like the mental world of Ebenezer Scrooge, is replete with ghosts,” he says. “There are ghosts of habitats, predators, parasites, competitors, mutualists, and conspecifics past, as well as ghosts of meteors, volcanic eruptions, hurricanes, and droughts past.”18 These ghosts may reside in our genetic attic, but sometimes they speak to us, whispering the past is prologue.
This view, based on behavioral ecology or sociobiology, has its critics, who are suspicious that such thinking evokes genetic predeterminism. In recent years, though, the proponents of biophilia and its doubters appear to have come to something approaching agreement: long-term genetics may lay down a likely pathway for brain development, but the outcome is also determined by the more current environment —by attachment to nurturing human beings, for example. Orians argues that all adaptations are to past environments. “They tell us about the past, not the present or the future. . . . As Ebenezer Scrooge discovered, ghosts, no matter how inconvenient they may seem to be, can yield positive benefits.” He adds: “People have clearly intuitively understood the restorative value of interactions with nature for a long time.” Witness the gardens of ancient Egypt, the walled gardens of Mesopotamia, the gardens of merchants in medieval Chinese cities, the American parks of Frederick Law Olmsted, or even the choices we make when picking sites for our homes and our visual responsiveness to certain landscapes. Orians and Judith Heerwagen, a Seattle-based environmental psychologist, spent years surveying people around the world, testing their preference for different images. The researchers found that, regardless of culture, people gravitate to images of nature, especially the savanna, with its clusters of trees, horizontal canopies, distant views, flowers, water, and changing elevations.
Another explorer of human biophilic tendencies, Roger S. Ulrich, professor of landscape architecture and urban planning at Texas A&M University, proposed his psychophysiological stress recovery theory in 1983, suggesting that our responses to stress are located in the limbic system, which generates survival reflexes. Citing Ulrich, physician William Bird, an honorary professor at Oxford University and chief health adviser for Natural England, the British government’s environmental arm, explains: “The fight or flight reflex is a normal response to stress caused by the release of catecholamines (including adrenaline) and results in muscle tension, raised blood pressure, faster pulse, diversion of blood away from the skin to muscle and sweating. All of these factors help the body to cope with a dangerous situation. However, without rapid recovery this stress response would cause damage and exhaustion with limited response to a repeat dangerous situation.”19 Evolution favored our distant ancestors who could recover from the stress of natural threats by using the restorative powers of nature.
One of the best explanations I have heard for this process came from the late Elaine Brooks, a California educator who worked for years as a biologist at the Scripps Institution of Oceanography. In Last Child in the Woods, I described how Brooks would often climb to the highest knoll in the last natural open space of La Jolla. She told me how, particularly in times of personal stress, she would imagine herself as her own distant ancestor, high in a tree, recovering from the threat of some predator. At those times, she would look out over the rooftops —which she would imagine to be the open plains of savanna—to the sea. She would feel her breath slow and her heart ease. “Once our ancestors climbed high in that tree, there was something about looking out over the land —something that healed us quickly. Resting in those high branches may have provided a rapid comedown from the adrenaline rush of being potential prey,” she told me one day, as we walked that land. “We are still programmed to fight or flee large animals. Genetically, we are essentially the same creatures as we were at the beginning. Our ancestors couldn’t outrun a lion, but we did have wits. We knew how to kill, yes, but we also knew how to run and climb —and how to use the environment to recover our wits.” She went on to describe modern life: how today we find ourselves continually on the alert, chased, as she put it, by an unending stampede of two-thousand-pound automobiles and four-thousand-pound SUVs. Inside our workplaces and homes, the assault continues: threatening images charge through the television cable into our bedrooms. Probably, at the cellular level, we have inherited the efficient antidote to all of this: sitting on that knoll, as Brooks did.
It should be added here that there are many contexts in which nature can offset toxic stress that may entail no physical danger. Short, quiet encounters with natural elements can simply calm us and help us feel less alone.