James Hamblin explains:
It is becoming increasingly clear that trees help people live longer, healthier, happier lives—to the tune of $6.8 billion in averted health costs annually in the U.S., according to research published this week. And we’re only beginning to understand the nature and magnitude of their tree-benevolence. In the current journal Environmental Pollution, forester Dave Nowak and colleagues found that trees prevented 850 human deaths and 670,000 cases of acute respiratory symptoms in 2010 alone. That was related to 17 tonnes of air pollution removed by trees and forests, which physically intercept particulate matter and absorb gasses through their leave.
(Photo by Flickr user Ian Sane)