This brief review of the literature focuses on ways in which contact with nature promotes human health and seeks to identify the mechanisms or pathways underlying this link. Twenty-one different pathways are identified and discussed. They include environmental factors, physiological and psychological states, and behaviors or conditions -- each empirically linked to nature and each with implications for specific physical and mental health outcomes.
Some of the specific environmental factors linked to human health include certain chemical and biological agents. Many plants, for example, give off phytoncides (antimicrobial volatile organic compounds) known to reduce blood pressure, alter autonomic activity, and boost immune functioning. Other environmental factors with positive effects on immune functioning include negative air ions present to a high degree in forested and mountainous areas and near moving water. These ions are also linked with reduced depression. The sights and sounds of nature are also known to have positive physiological effects, including enhanced healing from surgery and a boost in immune functioning.
Psychological effects of nature include the experience of awe, enhanced vitality, and attention restoration. These effects are linked to increased resistance to infection and lowered risk of mortality. Attention restoration could theoretically prevent accidents caused by fatigue and reduce risky health-related behaviors such as smoking and drug or alcohol abuse. Contact with nature is also associated with stronger social ties, better sleep, and increased physical activity.
While the author indicates that some pathways may play a larger role than others in promoting human health, she also suggests that there is, perhaps, a central pathway. Specific criteria for a central pathway proposed by the author include the size of nature's impacts on health, an account for nature's specific health outcomes, and the fact that it subsumes other pathways. Applying these criteria, what emerges as a central pathway is enhanced immune functioning. The author recognizes that there may be others.
Presented in the final section of this review are some implications for promoting human health, including the importance of access to “everyday” nature – that is, the views and greenspaces where we live. The findings suggest a need for greenspaces that, not only provide opportunities for physical activities, but also invite quiet contemplation and promote feelings of deep relaxation, awe, and vitality. “Providing these green oases,” the author suggests, “especially in areas where health risks are high and landscaping is sparse, might be an inexpensive, powerful public health intervention and address persisting health inequalities.”
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