In Japan they call it shinrin-yoku, or forest bathing, the act of immersing oneself in the comforting vibes of a forest. In California I call it going to church. I have never been a religious person, but I've gathered from those who are that the feeling they have when in a temple or church is what I feel when in a forest.
It doesn't have to be a forest. It could be a desert, a mountain valley, or a beach, all of which work just fine. In a pinch a city park will do, any landscape dominated by natural features rather than man-made. I try to visit such places every day, places where the air itself seems designed to soothe.
Psychologists have long been aware of the calming effect of nature, but only recently has the science behind it been established. Japanese researchers have compared human physical responses in natural settings to those in urban settings. Important indicators of stress were measured, such as the amount of the stress hormone cortisol in the body, blood pressure levels, heart rate, and activity within the sympathetic nervous system. All were significantly lower when people were in natural settings. This had nothing to do with jogging or biking or some other form of strenuous exercise. The mere act of being out in nature did the trick.
None of this surprises me. We have, after all, evolved from and with nature, and it makes sense that we respond positively to it. On a molecular level we are not that different from everything else; most of what exists in nature swirls within us.
If there's ever been an argument for conserving natural areas all can agree on, this calming effect of nature might be it. Perhaps doctors of the future will prescribe a few weeks in the forest, at the mountains, or on the beach as a cure for what ails us. Maybe we'll be able to bill our insurance companies for such medicine. I'm not holding my breath, but for me it doesn't matter. I'll just continue to do what I've always done, forest bathing as often as I can.