The connection between trees, human health and well-being dates back millennia. The ancient Celts worshiped in sacred groves, believing the trees would protect them from physical and spiritual harm. In Hebrew and Christian scriptures a tree of life in the Garden of Eden imparted immortality. Potted conifers helped to cleanse the air inside tuberculosis sanatoriums of nineteenth century Europe.

In recent years, scientists studying urban forests have turned up links between exposure to green space and health benefits, including fewer deaths from heart disease and respiratory diseases, fewer hospitalizations, better infant birth weights and even less crime.

“We’ve had this intuitive understanding that nature is good for us. Now we’re backing it up on an empirical level,” said Geoffrey Donovan, a resource economist with the U.S. Forest Service Pacific Northwest Research Station in Oregon.

Donovan and others are digging into the underlying science to understand the relationship between nature and health, a step they say will help guide the design of healthier cities and suburbs.