1. The health benefits of time spent in nature have been the subject of intense study in recent years, and have proven to be broad. The largest meta-analysis of its kind, including data from 143 international studies published in the journal Environmental Research in 2018, concluded that increased green space exposure was associated with decreased cortisol (stress) levels, heart rate, diastolic blood pressure, HDL cholesterol, risk of pre-term birth, Type 2 diabetes and all-cause and cardiovascular mortality, and increased incidence of good self-reported health. Canada’s first large-scale nature prescription program, just launched in British Columbia, empowered health-care practitioners to formally prescribe time outdoors for the physical and mental health of patients. Side effects may include greater longevity, increased energy and improved pain management. https://www.nationalobserver.com/2020/12/07/canada-nature-prescription-program-outdoors-health

2. Some of the plausible pathways from contact with nature to improved health stem from specific environmental conditions. Natural environments contain chemical and biological agents with known health implications. Many plants release phytoncides — antimicrobial volatile organic compounds — which reduce blood pressure, alter autonomic activity, and boost immune functioning, among other effects (Komori et al., 1995; Dayawansa et al., 2003; Li et al., 2006, 2009). 

3. The air in forested and mountainous areas, and near moving water, contains high concentrations of negative air ions (Li et al., 2010), which reduce depression (Terman et al., 1998; Goel et al., 2005), among other effects (Table 2 in the Supplementary Materials). These environments also contain mycobacterium vaccae, a microorganism that appears to boost immune functioning (see Lowry et al., 2007 for review). 

4. The sights and sounds of nature also have important physiological impacts. Window views and images of nature reduce sympathetic nervous activity and increase parasympathetic activity (e.g., Gladwell et al., 2012; Brown et al., 2013), restore attention (e.g., Berto, 2005), and promote healing from surgery (Ulrich, 1984). Sounds of nature played over headphones increase parasympathetic activation (Alvarsson et al., 2010). Published online 2017 Jul 28: Int J Environ Res Public Health. 2017 Aug; 14(8): 851.  Doi: 10.3390/ijerph14080851

5. Park BM, et al. (2009). The physiological effects of (taking in the forest atmosphere or forest bathing): Evidence from field experiments in 24 forests across Japan.


6. Livni E. Trees Please: The Japanese Practice of ‘Forest Bathing’ Is Scientifically Proven to Improve Your Health. [(accessed on 26 April 2017)];2016 Available online: https://qz.com/804022/health-benefits-japanese-forest-bathing/

7. Li Q., Morimoto K., Kobayashi M., Inagaki H., Katsumata M., Hirata Y., Hirata K., Suzuki H., Li, Y.J., Wakayama Y., et al. Visiting a forest, but not a city, increases human natural killer activity and expression of anti-cancer proteins. Int. J. Immunopathol. Pharmacol. 2008;21:117–127. doi:10.1177/039463200802100113. 

8. Stigsdotter U.K., Ekholm O., Schipperijn J., Toftager M., Kamper-Jørgensen F., Randrup T.B. Health promoting outdoor environments—Associations between green space, and health, health-related quality of life and stress based on a Danish national representative survey. Scand. J. Public Health.2010;38:411–417. doi: 10.1177/1403494810367468.