The idea that getting out to the country is good for our health is as old as medicine itself. Modern science seems to bear out the idea, with a host of studies demonstrating the therapeutic effects of exposure to nature. Japanese scientists have demonstrated that long walks in the woods produce lower levels of cortisol—a hormone linked to stress—and reduce blood pressure. 

As to why nature makes us feel better, the verdict is still out. In 1984, biologist E.O. Wilson proposed the “biophilia” theory, which suggests that we evolved to prefer the sight of resource-rich environments—the blue of clean water, the green of fertile fields and forests—and that this has led to a salutary neural response.

On a gut level, many of us feel that organic things are just ineffably better th...