Most people realize that trees provide a number of environmental and economic benefits, but few realize that trees also provide health benefits for those living near them. However, a recent national study, conducted by the United States Forestry Service and the Davey Institute, is likely to change that. Given that Los Angeles is bathed in the country’s most polluted air, this study is especially important for those of us living and working in Southern California. (BARBOZA, 2014)
Unlike many other studies, which have concentrated on quantifying the ability of trees to reduce energy costs, sequester carbon or improve water quality, this study sought to quantify the physiological benefits that humans enjoy, thanks to the air-cleaning abilities of trees. As explained in the study, trees not only help to reduce the costs associated with health care, but they actually reduce the rate of illness in the community and actually save lives.
According to the study, trees reduce national healthcare expenditures by nearly 7 billion dollars each year. More impressively, the study found that trees eliminate nearly 670,000 cases of acute respiratory symptoms. Nevertheless, the most impressive statistic produced by the study showed that trees were responsible for preventing approximately 850 human deaths each year.
How They Help
Trees provide these health benefits (among other ways) by helping to remove pollution from the air. Trees remove particulates in the air, such as soot, easily enough – the pollutants simply stick to the bark, leaves and branches of the trees. Eventually, the particulates fall to the ground or they are washed away with the rain. Trees remove toxic gases, such as carbon monoxide and sulfur dioxide, by drawing the pollutants into small pore-like openings called stomata. Once inside the trees, different species safely quarantine or discard the substances in a variety of ways. Additionally, trees reduce the local air temperature, which reduces the amount of pollutants entering the atmosphere by reducing the rate of the pollution-causing chemical reactions take place.
While 34 percent of the continental United States is covered with trees, the amount of coverage varies from one area to the next (as of 2006, 21 percent of Los Angeles was covered by tree canopy). (Million Trees LA, 2006) While some urban environments, particularly those in the southeast and along the Atlantic seaboard, have robust tree populations, most urban areas have fewer trees than rural areas do. Ironically, these urban areas are the ones most in need of the services of trees. While the bulk of the air pollution removed from the air by trees takes place in the relatively unpolluted air of rural areas, the greatest positive health effects (in terms of both reduced illnesses and reduced costs) occurred in urban areas.
You can read the entire study here (PDF).
BARBOZA, T. (2014). L.A., Central Valley have worst air quality, American Lung Assn. says. Retrieved from LAtimes.com: http://www.latimes.com/science/la-me-0430-air-pollution-20140430-story.html
David J. Nowak, ,. S. (2014). Tree and forest effects on air quality and human health in the United States. Environmental Pollution.
Million Trees LA. (2006). Tree Canopy Analysis. Retrieved from milliontreesla.org: http://www.milliontreesla.org/mtabout3.htm