Nebraskan Julius Sterling Morton believed that planting trees could save America, and he convinced the state to celebrate Arbor Day in April 1872. By planting trees, Morton hoped to prevent erosion, preserve the topsoil, and break some of the raging winds across the plains. While Arbor Day wasn’t officially adopted in the United States until 100 years later, Morton was onto something. A recent study finds that trees can save America, though not quite in the ways Morton envisioned. Instead, the study found that trees contribute to good health.
Researchers led by David Nowak, a forestry researcher, conducted four analyses on the county level, comparing urban to rural areas to understand the overall impact of trees on human health. The analyses included a look at the daily “total tree cover and leaf area index,” “the hourly flux of pollutants to and from the leaves,” “the effects of hourly pollution removal on pollutant concentration in the atmosphere,” and “the health impacts and monetary value of the change in [pollutants].”
The study provides some surprising results. Trees scrub the air of pollution, removing as much as 17.4 million tons of pollution in 2010. This translates to health savings of about $6.8 billion annually. In addition to saving money, trees prevent as many of 850 deaths and help avoid 670,000 cases of acute respiratory symptoms.
While more trees are located in rural areas, those which have put down roots in urban areas work harder and have a bigger influence. “Thus, 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 write. "The greatest monetary values are derived in areas with the greatest population density (e.g. Manhattan)."
Trees contribute to overall health, but the monetary savings from U.S. trees alone amounts to $86 billion annually. While the authors admit that their analysis has some limitations, the message seems clear: Trees do change American lives.