NYT:

In a series of studies, scientists found that when people swap their concrete confines for a few hours in more natural surroundings — forests, parks and other places with plenty of trees — they experience increased immune function.

Stress reduction is one factor. But scientists also chalk it up to phytoncides, the airborne chemicals that plants emit to protect them from rotting and insects and which also seem to benefit humans.

One study published in January included data on 280 healthy people in Japan, where visiting nature parks for therapeutic effect has become a popular practice called “Shinrin-yoku,” or “forest bathing.”

Forest bathing was once almost possible in Freeway Park, but now all of the big trees are gone. There is no place in the heart of the city where one can come even close to enjoying the benefits of being around many trees—trunks, bark, branches, and leaves.

• Casey Yee