Our Health and the Planet

“Aren’t environmental issues primarily about health? Detractors like to trivialize environmentalists as “tree huggers,” but the bottom line is that pollution makes us sick, right? Wouldn’t people care more if they had a better understanding of that?” — Tim Douglas, Stowe, Vt.

The potential disastrous health effects of global warming are staggering. Carbon dioxide emissions may not be directly responsible for health problems at or near their point of release, but in aggregate they can cause lots of distress. According to the Center for Health and the Global Environment at Harvard Medical School, climate change over the coming decades is likely to increase rates of allergies, asthma, heart disease and cancer, among other illnesses. Also, it is quite likely that, as global temperature rises, diseases that were previously found only in warmer areas of the world may show up increasingly in other, previously cooler areas, where people have not yet developed natural defenses against them. And the loss of rain forest that accompanies increases in temperature means less access to undiscovered medicines and degradation of the environment’s ability to sustain our species.

According to the International Journal of Environmental Research and Public Health, a review of the evidence shows strong associations between nature exposure and health, which include but are not limited to:

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Affective State: “In a study investigating forest bathing, or shinrin-yoku, researchers found that time spent in forests was associated with a reduction in reported feelings of hostility, depression, and anxiety among adults with acute and chronic stress. Another study examining walking in different environments observed the largest and most consistent improvements in psychological states associated with forest walks. Forest bathing may play an important role in health promotion and disease prevention.”

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Blood Pressure: “Two meta-analyses found evidence suggesting that exposure to a natural environment reduced blood pressure. Song et al. reviewed the research in Japan from 52 studies on the physiological effects of nature therapy and found overwhelming evidence that blood pressure levels decreased when participants were exposed to a natural environment. Decreases in both systolic and diastolic blood pressure levels were observed across young healthy populations, as well as populations with hypertension. This suggests that forest walking may lead to a state of physiological relaxation. The authors found that both systolic and diastolic blood pressure taken in the forest environment were significantly lower than in non-forest environments.”

Immune Function: “In Japan, forest bathing has been positively associated with human immune function… A potential pathway for improved immune function is exposure to phytoncides (a substance emitted by plants and trees to protect themselves from harmful insects and germs), which could decrease stress hormones in the human body and increase NK cell activity. Additionally, the findings indicated that a day trip to a forest park also increased the levels of intracellular anti-cancer proteins.”

Mental Health: “Novel research has examined green outdoor settings as potential treatment for mental and behavioral disorders, such as attention-deficit/hyperactivity disorder (ADHD). One study demonstrated associations between green space exposure and improvement in behaviors and symptoms of ADHD and higher standardized test scores. A recent systematic review found significant evidence for an inverse relationship between green space exposure and emotional and behavioral problems in children and adolescents. In addition, natural features near schools, including forests, grasslands, and tree canopies, are associated with early childhood development, preschoolers’ improvement in socio-emotional competencies, and a decrease in autism prevalence.”

Obesity: “In one study of U.S. children, increasing greenness was associated with lower BMI z-scores and lower odds of increasing BMI z-scores between two follow-up times. Another study of schoolchildren in Spain found that greenness and forest proximity were associated with lower prevalence of being overweight or obese. One study found that street tree density was associated with lower obesity prevalence in New York City (U.S.) children. In an Australian study, the prevalence of being overweight was 27–41% lower in girls and boys who spent more time outdoors at the study baseline than those who spent less time outdoors.”

Conclusion: We found evidence for associations between exposure to nature and improved cognitive function, brain activity, blood pressure, mental health, physical activity, and sleep. Results from experimental studies indicated protective effects of nature exposure on mental health and cognitive function. Cross-sectional observational studies provide evidence of positive associations between nature exposure, higher levels of physical activity and lower levels of cardiovascular disease. Observational studies, natural experiments, and randomized controlled trials are starting to assess the longitudinal effects of exposure to nature on depression, anxiety, cognitive function, chronic disease, and other health outcomes. This review synthesizes recent literature, primarily from Western countries.

“Given the link between environmental problems and human health, more of us are realizing that what may seem like exorbitant up-front costs for environmental clean-up may well pay us dividends in the end when we see our overall health care costs go down and our loved ones living longer, healthier lives (ScientificAmerican.com).”

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Sources:

https://pmc.ncbi.nlm.nih.gov/articles/PMC8125471/

https://www.scientificamerican.com/article/environment-and-our-health/

http://chge.med.harvard.edu/

http://www.environmentalhealthnews.org/

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