Quantifying Nature: Introducing NatureScoreTM and NatureDoseTM as Health Analysis and Promotion Tools

Abstract

The Value of Nature Exposure in the 21st Century

Humanity is undergoing a monumental shift. People have rapidly moved from a largely natural, outdoor existence to life in built, urban settings. Most places where people live and work differ dramatically from the ones we occupied for 99.9% of human history, and our current surroundings often physically separate us from the natural world. Most people—over half globally and approximately 4 in 5 in the United States—now live in urban areas,¹ where nearby nature exposure tends to be limited² and unequally distributed across socioeconomic and racial/ethnic subgroups.^3-6 Adults in higher-income countries spend 80%-90% of their lives sedentary and indoors,^7-9 with 6 to 8 hours or more spent each day looking at screens.^10-12 The same is increasingly true for our developing youth,^10,13,14 who may experience poorer health across their life span as a result.¹⁵

Over the last 30 years, physicians, scientists, and journalists have come to suspect that we are experiencing a “nature deficit disorder,” or “extinction of experience”.^16-22 With the loss of direct exposure to nature has also come diminished knowledge of where food comes from, an inability to recognize plants and animals, fewer opportunities to experience awe (being in the presence of something vast that transcends current understandings of the world), and a failure to develop positive emotions and empathy toward other people and the non-human world.^23-25

In response to growing concerns about this radical shift, scientists worldwide have studied how nature exposure is associated with human health.^26-31 The links between declining nature exposure and increasing depression, anxiety, heart disease, and premature mortality are increasingly clear.^26,32 A large and growing body of scientific literature demonstrates that exposure to nature, broadly encompassing green spaces, trees, parks, water bodies, deserts, wilderness areas, wildlife, and more,^30,33 is associated with measurable and meaningful benefits to dozens of facets of psychological and physical health.^31,33-35 These benefits can follow from nature exposure in a variety of forms, from passively viewing nature from a park bench to walking along a tree-lined street or practicing shinrin-yoku (“forest bathing”)³⁶ in an urban forest. At a population level, the presence of nature has also been linked to important societal benefits, such as higher property values,³⁷ lower healthcare expenses,^38,39 lower levels of air pollution, noise, and heat,^40-43 as well as lower crime rates,^44,45 enhanced social mobility,⁴⁶ more cohesive communities,^47-50 and resilience to public health crises, such as the COVID-19 pandemic.^50,51 These beneficial associations are believed to result from natural areas mitigating environmental hazards, restoring cognitive capacity, reducing stress reactivity, facilitating interactions with commensurate microbiota, and promoting healthy behaviors, such as physical activity and social interaction.^30,34,52,53

Like exercise, sleep, and a healthy diet,⁵⁴ nature exposure may well be a necessary health behavior to promote longevity, prevent disease, and enhance wellbeing.^55-57 “Nature prescribing” by healthcare providers, a growing movement, can serve as a tool for health promotion with minimal cost, side effects, equipment needs, or training requirements. Few medications or existing interventions can match these qualities. For instance, the American Heart Association’s “Life’s Essential 8” asserts that the following can help achieve an “ideal” cardiovascular health: a healthy diet, ≥150 minutes of moderate exercise or ≥75 minutes of vigorous exercise per week, not smoking or vaping, sleeping 7 to 9 hours each night, maintaining a healthy body mass index, and regularly checking and maintaining cholesterol, fasting blood sugar, and blood pressure levels.⁵⁴ Nature exposure might be comparable to several of these recommendations in terms of potential health benefits and come with fewer barriers to starting and maintaining a regular practice.