In our increasingly urbanized world, it turns out that a little green can go a long way toward improving our health, not just that of the planet.
That could mean something as simple as a walk in the park or just a tree viewed through a window. It's not necessarily the exercise that is the key. It's the refreshing contact with nature and its uncomplicated demands on us.
Here is how it works: Modern life — commuting, computing, paying taxes — can place a burden on our brains and bodies. In recent years, scientists at the University of Illinois at Urbana-Champaign's Landscape and Human Health Laboratory and elsewhere have compiled evidence that suggests that a connection to nature is vital to our psychological and physical health because it helps recharge our brains so that we're better able to cope with the stresses in life.
This ingrained dependence on our environment is like that of any other animal it seems, because like other organisms, we evolved to thrive in our natural surroundings, said Frances (Ming) Kuo, director of the laboratory. Kuo's colleague William Sullivan discussed this topic earlier this month at a symposium, "Exploring the Dynamic Relationship Between Health and the Environment," at the American Museum of Natural History here.
"It's out there in real life; people can see it," Kuo told LiveScience.
In 2007, it was estimated that more than half of the world's population lived in urban, rather than rural, areas for the first time in human history.
Urban environments, with their traffic and harried pace, are a constant drain on our mental resources because we have to work to pay attention to a myriad of stimuli.
Similarly, animals taken out of their natural habitats can start to degrade mentally and physically — parenting skills decline, aggression increases and playful activity stops. Some of these same symptoms can be seen in particularly stressed human populations.
Nature, on the other hand, is a little kinder to our craniums.
"In evolution, those of us who found it — nature — sort of inherently interesting probably were more likely to remember where the berries were" or where a specific threat was, Kuo explained. "And so the idea is that we're selected for being interested in relevant natural phenomena."
So thanks to evolution, we don't have to work to pay attention to nature — it, well, naturally interests us. Several studies conducted by Kuo and her colleagues show that exercising this easy interest in nature, even unconsciously, seems to improve our ability to pay attention and react to stressful situations.
Green vs. non-green
In a 2001 study detailed in the journal Environment and Behavior, Kuo and her colleagues surveyed parents of children aged 7 to 12 who had been diagnosed with an attention deficit disorder. They asked the parents to rate activities that seemed to alleviate their child's symptoms and which seemed to aggravate them.
They found the children functioned better after a "green" activity (i.e. one that likely took place in a natural setting, such as fishing or soccer) than a "non-green" one (such as watching TV or playing video games).
Kuo and her colleagues think the improvement stems from nature's ability to capture our attention involuntarily, giving the hard-working, overtaxed part of our brain used to voluntarily focus our attention on more demanding tasks a break, essentially allowing it to recharge.
A series of studies conducted by Kuo's lab in public housing around Chicago found similar results.
The researchers interviewed a number of female residents of public housing projects. Each subject was randomly assigned to rooms that had views of trees or grass outside and ones that looked out on barren courtyards.
People living in public housing "have fatiguing lives, and not particularly rejuvenating home circumstances," Kuo said. "They're just much more likely to be at the end of their rope on any given day."
Through the interviews, the researchers found that residents whose apartments were exposed to green spaces reported fewer aggressive conflicts, including domestic violence, than those who that had no views of green spaces. They also procrastinated less on major goals, such as finding a job or a new home, and were less likely to think their problems were unsolvable.
Having our capacities for attention restored, "allows us to be our best selves, so we are able to inhibit impulses that we want to be able to inhibit; we can take the long view of things; we can think better," Kuo said.
These benefits can reach beyond an individual person to the community or even society, by strengthening community ties and helping disadvantaged populations better cope with and solve their problems.
"When you take the individual effects, and then you magnify it by the fact that people around you share that same environment, you can actually imagine that they're really, really significant effects," Kuo said.
For example, greener areas also had lower crime rates and more socializing between neighbors.
Where there are trees and other greenery outside buildings, "what you see is people are using the outdoor spaces more often, and as a consequence, they actually run into each other," Kuo said. And with more people using the spaces, there are more "eyes on the street," which could deter crime.
The green spaces are "kind of the seed around which strong neighborhoods grow," Kuo said.
Access to green spaces can lead to improvements in physical health too, other studies have found.
One study of 80- to 85-year-olds conducted in Tokyo found that those with access to green space had a lower rate of mortality, even when socioeconomic status was taken into account.
Another study in the United Kingdom found that the health disparities normally seen between the wealthy and non-wealthy disappeared when access to green areas was factored in.
One study conducted in Indianapolis found that children in greener neighborhoods had a reduced risk of being overweight or obese.
"All their findings are kind of pointing in the same direction," Kuo said.
Kuo said that the connections between green spaces and health could be applied to daily life, both at the individual and community levels.
After a hard day at work, maybe do a little gardening before starting in on the taxes, or, if you're a student, play some soccer before studying for that test. (Kuo said that nature isn't the only thing that can help us rejuvenate in this way — reading a book for pleasure, listening to music or spending quiet time with friends and family can also help by easily engaging us while letting our brains rest.)
Cities and other communities can also use this information, and several already have.
Chicago recently undertook a $10 million tree-planting initiative — the largest in city history. They also used a large chunk of the federal funds for rehabbing the city on landscaping, which Kuo was told was done partly because of the findings of her studies.
Washington, D.C., Philadelphia and New York also have city greening initiatives running or in the works.
"So it seems like policy folks are paying attention," Kuo said.
But even with the benefits that Kuo and others have seen their studies, there still may be more links not yet discovered.
"We're finding all these ways in which the environment matters to us and affects, but I don't think we're done," she said.