In January, with the landscape barren, it’s hard to imagine that living near a tree-lined street can have a positive impact on your health. But, in a new study by the U.S. Forest Service, researchers found that the presence of trees may be linked to human health.
Numerous studies have shown that exposure to the natural environment improves human health. In one study, patients recovered faster from surgery and took fewer pain medications in a room with a view of a natural scene than those with a view of a brick wall.
Other studies have found a positive association between “greenness” and lower overall mortality. In a study that looked at health records of almost 350,000 people, those living in greener areas were less likely to be diagnosed with 15 of the 24 health outcomes examined.
A recent natural phenomenon provided researchers with an opportunity to examine this causal link. Since 2002, over 100 million emerald ash trees in the U.S. have been killed by a type of beetle. This huge loss of trees, which occurred primarily in the east and mid-west, provided researchers with a unique opportunity to evaluate the effect of changes to the natural environment on public health.
In particular, the study focused on how the loss of trees influenced mortality related to cardiovascular disease and lower-respiratory-tract illnesses (e.g., bronchitis or pneumonia).
These two health issues were chosen because they are the #1 and #3 killers in the U.S. and these types of deaths are linked to trees. Studies have shown that the natural environment helps reduce stress, increase physical activity and improve air quality, variables that are linked to both health outcomes.
Data was collected from 1990 to 2007 from 15 states that had diseased emerald ash trees. Analysis of changes in ash tree canopy along with mortality statistics were conducted in 2011 and 2012.
Scientists found that widespread death of ash trees led to an increase in deaths related to cardiovascular disease and lower-respiratory-tract illness. Conversely, in counties with more ash trees, the rate of death from both of these health issues was lower.
Over a 5 year period, researchers estimated that the number of excess deaths due to the loss of ash trees to be almost 22,000 (6,113 from respiratory illness, 15,080 from cardiovascular disease).
Lead author Geoffrey Donovan said, “There’s a natural tendency to see our findings and conclude that, surely, the higher mortality rates are because of some confounding variable, like income or education, and not the loss of trees. But we saw the same pattern repeated over and over in counties with very different demographic makeups.”
Interestingly, the effect of tree loss on public health was more pronounced in wealthier counties. One reason may be that peopling living in wealthier counties have greater access to ash trees so the death of this foliage has a greater impact on the population. Also, the existence of trees can increase the value of homes in a wealthy community. In an urban setting, parks can attract crime so the local residents don’t benefit as much from the foliage.
While the study did not provide any insight as to why trees would improve public health, study authors offered a number of mechanisms including improving air quality, reducing stress, increasing physical activity, moderating temperature and buffering stressful life events.
The Bottom Line
Although I’ve lived in several areas of the country, no matter where I’ve made a home, my number one priority has been to live near trees and greenery. Being close to nature provides me with a refuge from the day’s stressors and allows me to get grounded.
While I’m not surprised that a forest pest that destroys thousands of trees would have a negative impact on the community, I didn’t think this event could be associated with an increase in death.
What this study and others point out is the importance natural surroundings to our physical and mental health. What is you work or live in a city far away from nature? Decorate your space with some plants or flowers. On the weekends, jump in the car and drive to a park where you can run, walk or bike. Just be sure to regularly get your “fix” of Mother Nature as part of a healthy lifestyle.
David H. Rahm, M.D. is the founder and medical director of The Wellness Center, a medical clinic located in Long Beach, CA. Dr. Rahm is also president and medical director of VitaMedica. Dr. Rahm is one of a select group of conventional medical doctors who have education and expertise in functional medicine and nutritional science. Over the past 20 years, Dr. Rahm has published articles in the plastic surgery literature and educated physicians about the importance of good peri-operative nutrition.