Trees: Good for the Planet, Good for Your Health

by Hanna Morris – August 14, 2014

First-of-its-kind study quantifies urban trees’ benefits to public health

Trees planted in metropolitan areas can feel like little more than ornamentation, an artsy effort to enliven the urban jungles of concrete and asphalt. But it turns out that city trees have real, quantifiable health benefits that exceed expectations. According to a new study by the US Forest Service, some 850 human deaths and 670,000 incidences of serious respiratory illness are avoided each year within the United States thanks to our towering, green friends.

Photo by Mathew Knott, FlickrNew York City’s Central Park. According to the study, the value of a tree in terms of human health benefits increases with the density of population.

This is the first time scientists have quantified the exact amount of noxious air pollution removed by trees. The amount is substantial, weighing in at 17.4 million tons. With less harmful toxins floating around and irritating our lungs and sinuses, $7 billion per year is saved in unneeded trips to the doctor.

The value of a tree in terms of human health benefits, the study says, increases with density of population. So, if more trees are planted in New York City as opposed to, say, Ithaca, a far greater health benefit can be achieved. “In terms of impacts on human health, trees in urban areas are substantially more important than rural trees due to their proximity to people,” says Dave Nowak of the US Forest Service’s Northern Research Station in a press release announcing the report.

Unfortunately, there aren’t as many trees as there could be in many American cities today. This poses a serious national health risk. “With more than 80 percent of Americans living in urban areas, this research underscores how truly essential urban forests are to people across the nation,” says Michael T. Rains, director of the Forest Service’s Northern Research Station and the Forest Products Laboratory. 

So, how exactly do trees manage to remove such an incredible amount of dangerous air pollutants? The science lies in the green, glossy surface of each tree’s leaves. “Trees remove air pollution by the interception of particulate matter on plant surfaces and the absorption of gaseous pollutants through the leaf stomata,” the study explains. While this process is well documented, the new study is first to calculate the total public health benefit from tree canopy.

“Air pollution is a significant problem in the United States that affects human health and well-being, ecosystem health, crops, climate, visibility and man-made materials,” the study asserts. If these other variables are considered in addition to human wellbeing, the study’s researchers estimate a whopping 13-fold increase in the value of trees, to an estimated $86 billion.

The study advises American urban planners and policymakers to consider not only the aesthetic value of urban forests, but also their practical function and medical benefits. The new numbers prove that trees matter when it comes to human health, especially in highly populated urban areas. Evidently money does grown on trees.

Hanna Morris
Hanna Morris is an intern at Earth Island Journal. She is studying Society and Environment with a focus in Global Environmental Politics at the University of California, Berkeley. Hanna is the communications director for the UC Berkeley Student Environmental Resource Center and founder of the Communicating Sustainability DeCAL.

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