The Effects of Trees on Human Health 

Want to increase longevity?  Consider planting trees.

Set the apple down. The tree might be able to ward off the doctor.  Trees provide shade for sidewalks, absorb air pollution, reduce noise pollution from vehicles, and are simply beautiful to look at. Furthermore, trees benefit the environment because they remove carbon from the atmosphere, which warms the climate. 

The benefits of all that flora add up in terms of health.  According to a recent Portland, Oregon, research, fewer deaths occurred in neighborhoods where an organization had planted more trees.  The United States Forest Service researchers’ paper contributes to the growing body of studies on the advantages of living near greenery for health.  Its conclusions essentially suggest that legislators plant more trees. 

The study’s lead author, Geoffrey Donovan of the Forest Service, stated that urban trees “should be treated as an essential part of our public health infrastructure” and that it was published in the December 2022 issue of Environment International. 

Trees, after all, have a great deal of significance in our lives. The most evident is that trees help create oxygen for us to breathe and store carbon dioxide to keep our environment safe. However, research indicates that trees also have other significant advantages. 

The most well-studied benefit of nature exposure is that it appears to help reduce stress, rumination, and anxiety. Much of the study has taken place in the forests.  In a recent study, following a 15-minute walk through an urban or forest setting, 585 young adult Japanese participants commented on their moods. About twelve participants strolled through each of the 52 distinct locations of the woodlands and urban centers across the nation. When compared to walking in an urban environment, all of the participants who were walking in a forest reported feeling more vigorous and experiencing less anxiety, aggression, exhaustion, bewilderment, and depression symptoms.  For those who were already more nervous, the effects were significantly more pronounced when in urban settings. 

According to the authors, “walking through garden and tree forests has significant psychological benefits, and forest environments are expected to have very important roles in promoting mental health in the future.” In fact, a number of other studies indicate that intentionally spending time in the woods, or “forest bathing,” may help us cope with the pressures and demands of life. 

In a different study, participants from Poland looked at either an urban forest in winter or an unforested urban landscape for fifteen minutes. There was no other flora beneath the trees in the forest; thus, there was no greenery–the urban environment was made up of buildings and roads. The trees in the forest had straight trunks and no leaves because it was winter. The participants answered questionnaires on their feelings and moods both before and after. Compared to those who looked at the urban landscape, those who looked at a winter forest reported far improved moods, more positive emotions, more energy, and a larger sense of personal repair thereafter.  It’s possible that some of these advantages stem from the ways that trees and forests influence our brains. According to one study, those who live close to trees have stronger “amygdala integrity,” or a brain structure that can withstand stress. 

Short visits to forests appear to strengthen our immune systems, according to a study conducted by the Centers for Disease Control and Prevention. According to one study, visiting forests as opposed to cities was associated with lower levels of pro-inflammatory cytokines, granzyme B, and perforin expressions in elderly patients with chronic obstructive pulmonary disease. These findings are all linked to improved immune function. A previous study indicated that trees may boost immunity because of particular aromatic molecules they release, however, it’s unclear exactly why this would be the case. 

Additionally, trees appear to benefit heart health. In one study, participants took walks in an urban setting one day and a forest the next, and researchers recorded the differences in their physical responses. Strolling among trees reduced people’s blood pressure, cortisol levels, heart rates, and sympathetic nervous system activity (associated with stress)while elevating their parasympathetic nervous system activity (associated with relaxation) in contrast to walking in cities. Since improved heart health is associated with all of these physiological markers, walking in the woods may be beneficial to cardiovascular health. 

People who live near trees report better overall health than those who live near green, grassy spaces, though it’s possible that natural spaces, in general, have more of a role in these health benefits than trees specifically. Additionally, a different study discovered that women who reside in regions where tree loss has occurred are more likely to develop cardiovascular disease according to the CDC. 

In a recent study, researchers examined Chicago’s crime data and assigned a score to each census tract. They then contrasted that with each tract’s percentage of enclosed parkland and tree canopy cover. They discovered that crime rates decreased in a number of categories—11.3% for robberies, assaults, and drug-related offenses, and 10.3% for battery—for every 10% increase in tree canopy cover.  These results persisted even after adjusting for variables that could have influenced the outcome, such as the residents’ socioeconomic status, level of education, unemployment, and poverty. Furthermore, having a park nearby had no effect on other types of crimes, despite the fact that burglary rates decreased by 6.3% for every 10% increase in park space. Put differently, trees were a better indicator of decreased crime than parks. 

According to earlier studies, vegetation around homes can help lower people’s levels of fear, rudeness, and aggression—all of which can be seen as risk factors for crime. Additionally, trees may entice people to leave their houses by putting more “eyes on the street,” which helps to lower crime rates. In any case, planting some trees could be a useful strategy for maintaining community safety. 

Numerous studies have shown that being in nature makes us feel kinder towards other people, and many of these studies involve trees. 

In one experiment, scientists gave a group of college students one minute to gaze up at a tall structure or a grove of towering eucalyptus trees. Researchers discovered that awe—a sense of wonder and being in the presence of something greater than oneself—was more prevalent in students who studied the trees.  Later, the students who had been in awe of the trees helped pick up more pens than the students who had only looked at the building when one of the experimenters pretended to drop a bunch of pens by accident. 

Researchers also discovered that people were more inclined to assist someone who had misplaced a glove if they had just been strolling through a park with trees as opposed to being close to the park’s entrance. Regrettably, the advantages of trees over green space in general are not mentioned in this study or in many others. Therefore, the precise role that trees play in encouraging helpful and kind behavior is unknown. However, it’s likely that their presence improves social interactions at the very least. 

For all these reasons, let’s all make interacting with trees a nearly daily habit. Whether it’s as simple as gazing out your office window or going for a quick walk around the block to see your favorite oak, let’s give the trees in our immediate environment a quick pat or hug for improving our health and being our allies in lowering global warming through the process of afforestation and reforestation, which is frequently hailed as one of the most important answers to the eradicating climate crisis. 

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