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 trees’ 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 tons of air pollution removed by trees and forests, which physically intercept particulate matter and absorb gasses through their leaves.
The culmination of the research is the map below, delineating where trees are most protective. In general, the more trees are in an area, the more pollution those trees remove. But they also remove more pollution per tree in areas where population density is high, and the health value derived from pollution removal is highest in urban areas.
“In terms of impacts on human health, trees in urban areas are substantially more important than rural trees due to their proximity to people,” the researchers wrote. “The greatest monetary values are derived in areas with the greatest population density (e.g. Manhattan).”