CommentaryOpen Access

Nature Contact and Human Health: A Research Agenda

is companion of
- From Intuitive to Evidence Based: Developing the Science of Nature as a Public Health Resource

Address correspondence to H. Frumkin, Dept. of Environmental and Occupational Health Sciences, University of Washington School of Public Health, Box 354695, Seattle, WA 98195-4695 USA; Telephone: 206-897-1723; Email:

E-mail Address: [email protected]

Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, Seattle, Washington, USA

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Gregory N. Bratman

Center for Conservation Biology, Stanford University, Stanford, California, USA

Center for Creative Conservation, University of Washington, Seattle, Washington, USA

School of Environmental and Forest Sciences, University of Washington, Seattle, Washington, USA

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Sara Jo Breslow

Center for Creative Conservation, University of Washington, Seattle, Washington, USA

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Bobby Cochran

Willamette Partnership, Portland, Oregon, USA

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Peter H. Kahn Jr

School of Environmental and Forest Sciences, University of Washington, Seattle, Washington, USA

Department of Psychology, University of Washington, Seattle, Washington, USA

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Joshua J. Lawler

Center for Creative Conservation, University of Washington, Seattle, Washington, USA

School of Environmental and Forest Sciences, University of Washington, Seattle, Washington, USA

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Phillip S. Levin

School of Environmental and Forest Sciences, University of Washington, Seattle, Washington, USA

The Nature Conservancy, Seattle, Washington, USA

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Pooja S. Tandon

Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, Seattle, Washington, USA

Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington, USA

Seattle Children’s Hospital, Seattle, Washington, USA

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Usha Varanasi

School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington, USA

Department of Chemistry, University of Washington, Seattle, Washington, USA

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Kathleen L. Wolf

School of Environmental and Forest Sciences, University of Washington, Seattle, Washington, USA

Pacific Northwest Research Station, USDA Forest Service, Seattle, Washington, USA

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, and

Spencer A. Wood

Center for Creative Conservation, University of Washington, Seattle, Washington, USA

School of Environmental and Forest Sciences, University of Washington, Seattle, Washington, USA

The Natural Capital Project, Stanford University, Stanford, California, USA

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Published:31 July 2017CID: 075001https://doi.org/10.1289/EHP1663Cited by:584

Abstract

Background:

At a time of increasing disconnectedness from nature, scientific interest in the potential health benefits of nature contact has grown. Research in recent decades has yielded substantial evidence, but large gaps remain in our understanding.

Objectives:

We propose a research agenda on nature contact and health, identifying principal domains of research and key questions that, if answered, would provide the basis for evidence-based public health interventions.

Discussion:

We identify research questions in seven domains: a) mechanistic biomedical studies; b) exposure science; c) epidemiology of health benefits; d) diversity and equity considerations; e) technological nature; f) economic and policy studies; and g) implementation science.

Conclusions:

Nature contact may offer a range of human health benefits. Although much evidence is already available, much remains unknown. A robust research effort, guided by a focus on key unanswered questions, has the potential to yield high-impact, consequential public health insights. https://doi.org/10.1289/EHP1663

Introduction

Humans are increasingly disconnected from nature. Most people—over half globally, and approximately four in five Americans—live in urban areas, where nature contact is typically limited (United Nations 2015). Surveys reveal that Americans spend greater than 90 percentage $greater than 90 percentage$ of their time indoors: most of that time is spent in buildings, and a smaller portion in vehicles (Klepeis et al. 2001). Screen time has reached daily averages of 1 h 55 min for children younger than 8 y old (Rideout 2013) and 7 h 38 min for those between 8 and 18 y old (Rideout et al. 2010). In 2016, the average “total media consumption” was 10 h 39 min per day among adults and was rising (Nielsen 2016). Park visitation, hunting, fishing, camping, and children’s outdoor play have all declined substantially over recent decades (Clements 2004; Frost 2010; Pergams and Zaradic 2008).

In this context, recent years have seen a blossoming of scientific interest in the benefits of nature contact for human health and well-being. Several recent reviews have summarized and evaluated the growing evidence base (Bowler et al. 2010; Hartig et al. 2014; James et al. 2015; Lee and Maheswaran 2011; Martens and Bauer 2013; Russell et al. 2013; Seymour 2016). This literature reveals an extraordinarily broad range of benefits, albeit with varying levels of evidentiary support (Table 1).

Table 1 Summary of evidence-based health benefits of nature contact.

No.	Health/well-being benefits	References
1	Reduced stress	Berto 2014; Fan et al. 2011; Nielsen and Hansen 2007; Stigsdotter et al. 2010; van den Berg and Custers 2011; van den Berg et al. 2010; Ward Thompson et al. 2016
2	Better sleep	Astell-Burt et al. 2013; Grigsby-Toussaint et al. 2015; Morita et al. 2011
3	Improved mental health:
	Reduced depression	Astell-Burt et al. 2014c; Beyer et al. 2014; Cohen-Cline et al. 2015; Gascon et al. 2015; Kim et al. 2009; Maas et al. 2009b; McEachan et al. 2016; Nutsford et al. 2013; Sturm and Cohen 2014; Taylor et al. 2015; White et al. 2013
	Reduced anxiety	Beyer et al. 2014; Bratman et al. 2015a; Maas et al. 2009b; Nutsford et al. 2013; Song et al. 2013; Song et al. 2015
4	Greater happiness, well-being, life satisfaction	Ambrey 2016; Fleming et al. 2016; Larson et al. 2016; MacKerron and Mourato 2013; Van Herzele and de Vries 2012; White et al. 2013
5	Reduced aggression	Bogar and Beyer 2016; Branas et al. 2011; Kuo and Sullivan 2001a, b; Troy et al. 2012; Younan et al. 2016
6	Reduced ADHD symptoms	Amoly et al. 2014; Faber Taylor et al. 2001; Faber Taylor and Kuo 2009; Faber Taylor and Kuo 2011; Kuo and Faber Taylor 2004; Markevych et al. 2014b; van den Berg and van den Berg 2011
7	Increased prosocial behavior and social connectedness	Broyles et al. 2011; Dadvand et al. 2016; de Vries et al. 2013; Fan et al. 2011; Holtan et al. 2015; Home et al. 2012; Piff et al. 2015; Sullivan et al. 2004
8	Lower blood pressure	Duncan et al. 2014; Markevych et al. 2014a; Shanahan et al. 2016
9	Improved postoperative recovery	Park and Mattson 2008; Park and Mattson 2009; Ulrich 1984
10	Improved birth outcomes	Reviewed by Dzhambov et al. 2014
11	Improved congestive heart failure	Mao et al. 2017
12	Improved child development (cognitive and motor)	Fjørtoft 2001; Kellert 2005
13	Improved pain control	Acutely (Diette et al. 2003; Lechtzin et al. 2010) and chronically (Han et al. 2016)
14	Reduced obesity	Bell et al. 2008; Cleland et al. 2008; P. Dadvand et al. 2014a; Lachowycz and Jones 2011; Sanders et al. 2015; Stark et al. 2014
15	Reduced diabetes	Astell-Burt et al. 2014a; Bodicoat et al. 2014; Brown et al. 2016; Thiering et al. 2016
16	Better eyesight	French et al. 2013; Guggenheim et al. 2012; He et al. 2015
17	Improved immune function	Li et al. 2006; Li et al. 2008a; Li et al. 2008b; Li et al. 2010; Li and Kawada 2011
18	Improved general health:
	Adults	Brown et al. 2016; de Vries et al. 2003; Kardan et al. 2015; Maas et al. 2006; Maas et al. 2009b; Stigsdotter et al. 2010; Wheeler et al. 2015
	Cancer survivors	Ray and Jakubec 2014
	Children	Kim et al. 2016
19	Reduced mortality	Coutts et al. 2010; Gascon et al. 2016b; Hu et al. 2008; James et al. 2016; Takano et al. 2002; Villeneuve et al. 2012
20	Asthma and/or allergies (studies show both improvements and exacerbations)	Andrusaityte et al. 2016; Dadvand et al. 2014a; Fuertes et al. 2014; Fuertes et al. 2016; Lovasi et al. 2013; Lovasi et al. 2008; Ruokolainen et al. 2015

Note: ADHD, attention-deficit hyperactivity disorder. The references in Table 1 are illustrative rather than exhaustive; they include both recent reviews and research reports and older, widely cited publications.

Despite this considerable body of evidence, key questions remain unresolved (Frumkin 2013). In this paper, we propose a research agenda on nature contact and health, with the aim of systematically identifying key questions that merit research attention.

Definitions and Scope

A necessary starting point is the definition of nature contact. In general, by “nature” we mean “areas containing elements of living systems that include plants and nonhuman animals across a range of scales and degrees of human management, from a small urban park through to relatively ‘pristine wilderness’” (Bratman et al. 2012), together with abiotic elements such as sunset or mountain views. We acknowledge that multiple definitions of nature are appropriate, varying with the form of nature contact being studied and the ways in which people relate to nature. We note the far-reaching discourse on nature as a social construct (Cronon 1996), which is beyond the scope of this paper. Similarly, there is a philosophical argument that humans are a part of nature, a view that calls into question any distinction between humans and nature, and hence the very possibility of “nature deficit” (Fletcher 2016). This argument is beyond the scope of this paper. The important category of animal contact, the subject of a large body of literature (Barker and Wolen 2008; Kamioka et al. 2014; Matchock 2015), is beyond the scope of this paper, as are the health benefits of the food and materials resulting from harvesting activities such as foraging, fishing, and hunting.

There are many forms of nature contact, varying by spatial scale, proximity, the sensory pathway through which nature is experienced (visual, auditory, etc.), the individual’s activities and level of awareness while in a natural setting, and other factors. Figure 1 displays various examples of nature contact along just two of these two scales, spatial and temporal. Much contemporary research focuses on greenspace as the exposure of interest, perhaps because of ease of measurement, but we take a broader approach, ranging from plants in a room to views through windows to camping trips to virtual reality imagery. Researchers must define and operationalize the specific form of nature contact they are studying. We return to this point below in our discussion of exposure assessment.

Plot showing forms of nature contact, namely, wilderness adventures; outings in natural settings; activities in natural settings, e.g. hiking, green exercise; land care activity e.g. civic stewardship; hands-on activities, e.g. gardening, fishing; residing in a green neighborhood; visiting a public garden; nature-based education; potted plants; window views of nature; and green school or work setting, along spatial scale (y-axis) and frequency (x-axis). — **Figure 1.** A spectrum of forms of nature contact.

With regard to outcomes, we take a broad definition of health, including physical and mental health, social well-being, academic and job performance, and happiness. The effects of nature contact on proenvironmental knowledge, attitudes, and behavior are the subject of an extensive body of literature (Collado et al. 2015; Wells and Lekies 2006) but are beyond the scope of this paper. Similarly, the outcomes we consider are limited to those affecting humans, excluding impacts of human–nature contact on other species or on natural systems more generally.

Methods

We assembled a multidisciplinary group at the University of Washington including expertise in epidemiology, environmental health, clinical medicine, psychology, ecology, landscape architecture, urban studies, public policy, and anthropology. The group studied published reviews of the nature–health connection, as well as primary research reports, and discussed research needs with end-users ranging from conservationists to nature preschool administrators to parks officials. Through iterative discussion and consensus formation, we sought to identify domains in which important questions remain unanswered, and in which research would advance the field. Within each domain, we identified specific research priorities.

Several principles guided the formulation of this research agenda. First, we recognized the value of diverse disciplines and professions. Second, we recognized the need to balance linear, reductionist approaches to research with complex, systems-based approaches, as advocated in other relevant domains of research (Dooris 2006; Liu et al. 2007), and we entertained research topics and strategies reflecting both approaches. Third, we recognized the need to integrate quantitative and qualitative data, and we entertained research topics that would draw on both kinds of data. Fourth, we emphasized research topics that are relevant and useful for decision makers and affected communities so that research results might have the greatest likelihood of being applied and benefiting people. Fifth, we emphasized research topics that, when appropriate, could engage affected populations both in defining research questions and methods and in conducting the research. For example, community-based participatory research, a well-established set of methods that improve the quality and relevance of research (Blumenthal et al. 2013; Jason and Glenwick 2016), has been applied to the study of nature contact (Bijker and Sijtsma 2017).

We identified seven domains of research on nature contact and health, as shown in Table 2. We considered ranking topics within each domain in order of importance but elected not to do so, mindful that in this highly interdisciplinary and context-dependent field, different investigators and decision makers likely differ in their scientific perspectives and information needs. However, we did identify top-level research questions based on scientific importance, tractability, and potential public health impact; these questions are designated with bold-face type in the listings that follow.

Table 2 Nature contact and health research domains.

Domain
1. Mechanistic biomedical studies
2. Exposure science
3. Epidemiology of health benefits
4. Diversity and equity considerations
5. Technological nature
6. Economic and policy studies
7. Implementation science

Domain 1: Mechanistic Biomedical Studies

A central aspect of health research is identifying the mechanisms that account for observed health effects: for example, the components of cigarette smoke that are carcinogenic and the immunologic pathways by which the smallpox vaccine confers protection. With respect to nature contact and health, the diversity of benefits suggests a broad, nonspecific physiological pathway of action, a multiplicity of pathways, or a combination of these. These pathways may have an evolutionary origin, as proposed by the biophilia hypothesis (Kellert and Wilson 1993; Wilson 1984). The mechanisms are only partially understood, and authors are unanimous in noting the need for deeper understanding (Dadvand et al. 2016; de Vries et al. 2013; Groenewegen et al. 2012; Hartig et al. 2014; Keniger et al. 2013; Lachowycz and Jones 2013; Shanahan et al. 2015b; Sullivan and Kaplan 2016). Such understanding would be invaluable in designing and testing strategies for delivering beneficial nature contact.

Several mechanisms have been hypothesized: psychological pathways, enhanced immune function, physical activity, social contact, and improved air quality. Each of these is considered below.

Psychological Pathways

Two complementary theoretical frameworks, both invoking psychological mechanisms, have been identified (Berto 2014). Stress Recovery Theory (SRT) emphasizes the role of nature in relieving physiological stress, whereas Attention Restoration Theory (ART) emphasizes the role of nature in relieving mental fatigue.

Stress reduction is both a health benefit in and of itself and a potential mechanism for other health benefits (Lovallo 2015). Some research has focused on short-term indicators: for example, experiments that expose subjects to stressful stimuli with and without nature contact and measure acute responses such as skin conductance and salivary cortisol levels (Parsons et al. 1998; Ulrich et al. 1991; van den Berg and Custers 2011). Other research has focused on a longer time frame: for example, comparing people living in more- and less-green neighborhoods with regard to subjective levels of stress (Nielsen and Hansen 2007; Stigsdotter et al. 2010; Ward Thompson et al. 2016) or ability to cope with stressful life events (van den Berg et al. 2010; Ward Thompson et al. 2016). The results consistently show that nature contact reduces stress; the relative importance of this direct pathway, and mediation through social contact, physical activity, and/or other factors, is less clear (Ward Thompson et al. 2016).

Attention restoration was proposed as a mechanism by Kaplan and Kaplan (Kaplan and Kaplan 1989; Kaplan 1995). This theory holds that excessive concentration can lead to “directed attention fatigue,” and that contact with nature—specifically with sufficient extent to feel immersed, and in ways that confer a sense of being away, that capture attention effortlessly (“soft fascination”), and that are compatible with personal preferences—engages a less taxing, indirect form of attention, thereby facilitating recovery of directed attention capacity. Empirical support has come from studies of attention deficit disorder (Faber Taylor and Kuo 2009, 2011; van den Berg and van den Berg 2011) and from diverse settings and populations (Brunson et al. 2001; Evensen et al. 2015; Li and Sullivan 2016). There is some evidence that the two mechanisms—stress reduction and attention restoration—may operate concurrently, yielding cognitive and affective benefits independently or through an interaction of the psychological processes involved (Li and Sullivan 2016).

Additional psychological mechanisms might interact with (or be independent of) stress reduction, attention restoration, or both. What is the role of awe—the sense of wonder, amazement, and smallness that may occur in response to perceptually vast stimuli (Keltner and Haidt 2003; Piff et al. 2015; Rudd et al. 2012; Shiota et al. 2007)? What is the role of mystery—the allure of seeing and knowing more by entering more deeply into a setting (Herzog and Bryce 2007; Szolosi et al. 2014)? How does nature contact influence the regulation of emotions (in adaptive and/or maladaptive ways) (Bratman et al. 2015a)? How might personality structure mediate the benefits of nature contact (Ambrey and Cartlidge 2017)? How might stress reduction and attention restoration operate differently in different groups, based on such factors as cultural background and socioeconomic position (Russell et al. 2013)?

Each of these constructs—stress reduction, attention restoration, awe, mystery—is based in theory. With increasing use of more precise psychophysiological measures in both laboratory and field settings, it is likely that they will evolve toward operationally defined constructs grounded in specific neural pathways.

Enhanced Immune Function

In a recent review, Kuo (Kuo 2015) argued that improved immune function accounts for many of the health benefits of nature, based on meeting three criteria: accounting for the magnitude of observed health benefits; accounting for the specific health outcomes observed; and subsuming other possible pathways. Nature contact may enhance immune function in at least two ways on very different time scales. First, consistent with the “hygiene hypothesis,” contact with microbial and other antigens in natural settings during particular developmental windows may modify immune function over the lifespan (Hanski et al. 2012; Kondrashova et al. 2013; Nicolaou et al. 2005; Rook 2013; Ruokolainen et al. 2015; Stiemsma et al. 2015), perhaps operating through effects on the microbiome (Lee and Mazmanian 2010). Second, short-term exposures to some natural substances (such as phytoncides from trees) have been associated with improved natural killer (NK) cell activity (Li et al. 2006, 2008a, 2008b, 2010; Li and Kawada 2011). Stress recovery and immune function mechanisms may not be distinct because of reciprocal relationships between these two physiologic systems (Irwin and Cole 2011; Nusslock and Miller 2016).

Increased Physical Activity

Physical activity confers a broad range of health benefits, including prevention and/or amelioration of obesity, cardiovascular disease, some cancers, diabetes, some mental illness, osteoporosis, gall bladder disease, and other conditions (Bauman et al. 2016; Lee et al. 2012; WHO 2010). Natural surroundings such as vegetated streetscapes, parks, and schoolyards are generally associated with higher levels of physical activity in both children and adults, a plausible mechanism for many of the observed health benefits of nature contact (Bancroft et al. 2015; Bingham et al. 2016; Calogiuri and Chroni 2014; Fraser and Lock 2011; Gray et al. 2015; Hunter et al. 2015; Kaczynski and Henderson 2007; Koohsari et al. 2015; Lee et al. 2015; O'Donoghue et al. 2016; Shanahan et al. 2016; Sugiyama et al. 2014). The mechanisms by which green surroundings might facilitate physical activity are not well understood; aesthetic preference may play a role (Shanahan et al. 2016). In children, evidence suggests that play in natural environments is associated with the development of motor skills such as balance and coordination, which in turn enable and predict physical activity (Fjørtoft 2001; Fjørtoft 2004). The dynamic and irregular characteristics of natural play spaces may explain this observation. Some studies have demonstrated a benefit from green neighborhoods independent of physical activity (Cohen-Cline et al. 2015; Fan et al. 2011; Feda et al. 2015; Nielsen and Hansen 2007), and some studies have found weak or no association between nature contact and physical activity (Gubbels et al. 2016; Hillsdon et al. 2006; Witten et al. 2008), suggesting that physical activity only partially accounts for health benefits. A challenge in interpreting these results is the possibility of reverse causation: people inclined to be physically active may seek recreation in green, outdoor settings. Moreover, the nature approaches physical activity approaches health $nature \to physical activity \to health$ pathway may vary across subpopulations, settings, levels of access, programming, and other factors.

A promising line of research regarding physical activity in natural settings pertains to “green exercise.” There is some evidence that physical activity in outdoor, natural settings confers more benefits than equivalent exertion in indoor or constructed settings (Barton et al. 2016; Coon et al. 2011). A better understanding of this phenomenon might help clarify the mechanisms by which nature contact benefits health.

Social Connectedness

Social connectedness is strongly associated with health (Kawachi et al. 2008). To the extent that nature contact promotes social connections, this may be a mechanism for associated health benefits (Maas et al. 2009a).

Support for this pathway comes from studies of prosocial behavior and of social capital (networks of social relationships and the norms of trust and reciprocity). With regard to prosocial behavior and attitudes, observational studies of residential greenness (Dadvand et al. 2016; Kweon et al. 1998; Sullivan et al. 2004) and of nearby parks (Fan et al. 2011) and experimental studies of brief nature exposures (Piff et al. 2015; Zelenski et al. 2015) have found an association between nature contact and prosocial outcomes. [One exception was a study of children in Kaunas, Lithuania, which found the opposite result (Balseviciene et al. 2014)]. With regard to social capital, studies have found that living in greener neighborhoods (de Vries et al. 2013; Holtan et al. 2015; Kemperman and Timmermans 2014) and using parks (Broyles et al. 2011; Home et al. 2012; Kaźmierczak 2013) are associated with greater social cohesion, with the strength and extent of social networks, or with both. Further research could clarify the ways in which natural features promote social connectedness and how this pathway interacts with other possible mechanisms of benefit.

Improved Air Quality

Air quality in rural or wilderness settings is generally superior to that in urban settings. In urban settings, tree canopy may reduce ambient levels of particulate matter and gaseous air pollutants, although most studies find this air-quality improvement to be slight (Nowak et al. 2013; Nowak et al. 2014). Moreover, any benefits must be weighed against potential disbenefits. Trees can in some cases worsen asthma (Andrusaityte et al. 2016; Dadvand et al. 2014a; Kimes et al. 2004; Lovasi et al. 2013), a likely result of pollen, soil fungi, other vegetation-associated allergens, the production of hydrocarbons (ozone precursors), or a combination of these factors (Grote et al. 2016). Trees can also impede air circulation, reducing the dispersion of air pollutants in urban canyons (Vos et al. 2013). To the extent that vegetation improves air quality, nature contact may offer protection against respiratory and cardiovascular disease.

Other Benefits of Nearby Nature

There are myriad other benefits of nearby nature that extend beyond these psychological and physical health mechanisms (Bolund and Hunhammar 1999; Livesley et al. 2016; Tzoulas et al. 2007). For example, urban vegetation, particularly trees, can reduce and filter storm-water runoff (Berland et al. 2017); regulate local temperatures, resulting in attenuated heat island effects (Bowler et al. 2010) and reduced energy demand (Nowak et al. 2017); provide pollination services (Hall et al. 2017; Threlfall et al. 2015) and wildlife habitat (Alvey 2006; Murgui and Hedblom 2017); reduce urban noise (Margaritis and Kang 2017); and sequester and store carbon (Davies et al. 2011). Larger natural areas outside of cities can contribute even more to carbon sequestration and storage, water filtration, and timber and game production.

Proposed research priorities

1.1

To what extent does stress reduction mediate observed health benefits of nature contact?

1.1a	Both short-term and long-term
1.1b	Which natural elements are most associated with stress reduction?
1.1c	Which markers of stress reduction are most useful in studying this effect?

1.2

To what extent does improved immune function mediate observed health benefits of nature contact?

1.2a	Both short-term and long-term
1.2b	Which natural elements are most associated with improved immune function?
1.2c	Which markers of immune function are most useful in studying this effect?
1.2d	What is the role of the human microbiome in mediating this effect?

1.3

To what extent does social connectedness account for, or mediate, observed health benefits of nature contact?

1.3a	Both short-term and long-term
1.3b	Which social arrangements or activities best optimize the benefits of nature contact through this pathway?

1.4

Does nature-based physical activity confer benefits above and beyond equivalent physical activity in nature-free settings?

1.4a

If so, which natural elements best account for the additional benefits?

1.5

For each of these potential mechanisms, how do other factors—demographic, social, biomedical, and ecological—affect the associations between nature contact and health?

Domain 2: Exposure Science

Exposure science (or exposure assessment) is: “the process of estimating or measuring the magnitude, frequency, and duration of exposure to an agent, along with the number and characteristics of the population exposed. Ideally, it describes the sources, pathways, routes, and the uncertainties in the assessment” (Zartarian et al. 2005). This discipline is a sine qua non of research on environmental impacts on people, whether the research focus is on pathogens, medications, toxic chemicals, social circumstances, or salutary exposures such as nature (Armstrong et al. 2008; Lioy and Weisel 2014; Nieuwenhuijsen 2003). Despite the centrality of exposure assessment in epidemiologic research, there is little agreement on how best to define nature contact for research purposes (Hunter and Luck 2015; Taylor and Hochuli 2017), let alone how to measure it (Mitchell et al. 2011; Wheeler et al. 2015). Various approaches have been used.

In some research, quantitative measures of natural elements serve as metrics of nature contact. Most recent research has measured greenspace; as noted above, greenspace is a more limited construct than nature contact. Two main kinds of exposure metrics are typically used: “cumulative opportunity” and distance (Ekkel and de Vries 2017). Cumulative opportunity refers to the total amount of nearby greenness (on the assumption that nature contact is proportional to this parameter). The most frequently used measure is the Normalized Difference Vegetation Index (NDVI), which assesses the density of photosynthetically active biomass based on satellite imagery (Gascon et al. 2016a; Rhew et al. 2011). Related metrics include the Enhanced Vegetation Index (EVI) (Huete et al. 2002), the Leaf Area Index (LAI) (Hu et al. 2014), the Building Proximity to Green Spaces Index (BGPI) (Li et al. 2014), and Object-Based Image Analysis (OBIA) using light detection and ranging (LiDAR), a laser-based imaging technology (MacFaden et al. 2012). To date, most studies have defined exposure to these quantitative measures based on the residential environment, an approach limited by spatial resolution and subject to misclassification (if people spend highly variable amounts of time at home). However, such data can be combined with Global Positioning System (GPS) tracking using devices such as smartphones to characterize individual exposure patterns as people move about during defined periods of observation (Chaix et al. 2013). The second quantitative approach, distance to greenspace, such as distance from home to a park, uses geospatial information. Few studies have compared cumulative opportunity and distance as exposure assessment strategies, but in studies that used both (Amoly et al. 2014; Coutts et al. 2010; Dadvand et al. 2014b; Jonker et al. 2014; Triguero-Mas et al. 2015), cumulative opportunity was a better predictor of health outcomes (Ekkel and de Vries 2017) [with at least one exception (Grazuleviciene et al. 2015)].

Semiquantitative measures of nature contact are also used. Examples include the presence or absence of plants in a classroom (Han 2009), the presence or absence of a tree view from a window (Ulrich 1984), the proportion of aquatic elements in a picture (White et al. 2010), or the density of fish in an aquarium (Cracknell et al. 2016). At a larger spatial scale, land-use or land-cover maps are often used. These maps classify landscape elements as “dense urban,” “forest,” “cropland,” and so on. An extensive listing of such databases is available for the United States at the U.S. Geological Survey Land Cover Institute web site ( https://landcover.usgs.gov/) and for the United Kingdom at the U.K. Office for National Statistics Generalised Land Use Database ( https://data.gov.uk/dataset/land_use_statistics_generalised_land_use_database). “Exposure” is approximated by integrating the time spent in each setting. Innovative technology permits more complex characterizations. For example, Google Street View can be used to assess the degree of nature encountered by a person at street level (Li et al. 2016). Similarly, social media data can help quantify visits to natural areas and behavior patterns within those areas (Sessions et al. 2016; Wood et al. 2013).

Standard approaches to exposure measurement share at least five limitations. First, they fail to capture variations in how people experience nature, nuances that may be highly relevant to health benefits (Kahn 2010). Suppose that one person sits in a car atop a seaside bluff and admires the view of the beach (while checking e-mail on a smartphone), a second person walks barefoot along the shore, enjoying not only the view but the feel of the sea breeze and the lapping waves, and a third person plunges in for a swim. The designation “beach contact” or a measure of “time at the beach” would fall far short of capturing the variation in their experiences. Among the relevant variables are the specific sensory modalities involved. Most research assumes that people’s contact with nature is visual, but other modes, such as auditory (Conniff and Craig 2016; Feld 2015), tactile, and olfactory, likely play a role. Specific forms of nature contact (Step 4 in Figure 2) need to be identified and measured.

Flow diagram. — **Figure 2.** A proposed framework for studying the health benefits of nature contact (adapted from Shanahan et al. 2015b).

Second, commonly used exposure measures have low reproducibility. Several studies have assessed the concordance among various measures of greenspace or tree canopy. These measures include direct observation; the use of Google Street View, Google Earth, or similar technologies; and the use of secondary sources such as land-cover data sets (Ben-Joseph et al. 2013; Charreire et al. 2014; Clarke et al. 2010; Pliakas et al. 2017; Rundle et al. 2011; Taylor et al. 2011). These measures have generally shown poor to fair agreement among the different approaches, suggesting a pervasive problem with measuring greenspace exposure (much less nature contact).

Third, commonly used exposure measures cannot quantify the “dose,” that is to say, what a person experiences during an episode of nature contact. If two people—one observant and highly attuned to nature, the other oblivious or distracted—both walk down the same forest path, they are likely to “absorb” differing levels of nature. “Nature connectedness” and/or awareness may be important (and highly culture-specific) mediators of “dose,” and through it of health benefits (Cervinka et al. 2012; Lin et al. 2014; Perrin and Benassi 2009). Even among people who are highly attuned to nature, perceptions may vary substantially (Beaudreau et al. 2011; Stier et al. 2017). Qualitative measures may have a role in addressing such limitations. Indeed, subjective ratings of vegetation or scenery (Hoyle et al. 2017; Seresinhe et al. 2015) may approximate “dose” as well as, or better than, objective measures. Emerging technologies such as smartphone apps that allow people to describe their surroundings may play an important role here (Schootman et al. 2016). Such crowd-sourced data need to be evaluated in terms of validity and generalizability.

Fourth, standard exposure measures typically focus more on physical than on temporal attributes. As in pharmacology and toxicology, the duration and frequency of exposure are important components of dose. If two people live in the same neighborhood with a certain amount of tree canopy, but one has lived there for 20 y and takes a 30-min walk each day, whereas the other just moved there a year ago and only ventures outside twice a month for 10 min each time, the two people have substantially different exposure profiles, a difference not captured by measures of their neighborhood street canopy.

Fifth, standard exposure measures are not grounded in the ecological elements most relevant to human health and well-being. What is it about a walk in the forest that confers benefits? Is it the vegetation type (Wheeler et al. 2015)? The level of biodiversity (Dallimer et al. 2012; Lovell et al. 2014; Rook 2013)? Does it matter if the trees are in leaf, or is a wintertime walk equally effective? Is wildness required, or does an orderly tree farm or agricultural field suffice? Precisely which elements of exposure need to be measured?

The choice of exposure metrics is consequential; there is evidence that research findings may vary with the exposure metrics used. For example, a study of green space exposure in relation to general health (Akpinar et al. 2016) found that “aggregated green space” performed differently from “forest,” and that urban green space performed differently from rural green space, in predicting mental health complaints.

Research is needed across all metrics of nature exposure to identify the metrics that are most accurate and precise and that best predict human responses of interest. The resulting insights, coupled with better knowledge of mechanisms of benefit, are needed to guide the provision of “the best dose of the best exposures.”

Proposed research priorities

2.1	Which metrics of nature best predict various health benefits?
2.2	For each such metric, what is its accuracy? What is its precision?
2.3	What is the role of subjective assessments, and of “nature connectedness,” in measuring nature contact?
2.4	How do exposure metrics vary in their performance by population and other factors?
2.5	What are the roles of duration and frequency of exposure in predicting health benefits?

Domain 3: Epidemiology of Health Benefits

The State of Research

Although recent research has identified many associations between nature contact and health, much remains to be learned. The body of epidemiologic research consists principally of three categories of study: true experiments, “natural experiments,” and observational studies, with observational studies accounting for the preponderance of the literature.

True experiments are the gold standard in science. In the nature and health domain, examples include clinical trials of nature imagery for pain relief during medical procedures (Diette et al. 2003; Lechtzin et al. 2010), of nature adventure therapy in the treatment of post-traumatic stress disorder (PTSD) in veterans (Gelkopf et al. 2013), of horticultural therapy in pain management (Verra et al. 2012), and of park walks in workplace stress management (de Bloom et al. 2017). The challenges of such experiments include their cost and the difficulty of assessing long-term outcomes; indeed, most reported trials have been limited to relatively short-term outcomes. Opportunities include the emergence of innovative techniques for measuring outcomes that can be readily applied in experimental settings (see below).

Natural experiments are study opportunities that resemble experiments but that arise through circumstances outside the investigator’s control (Dunning 2012). In the nature and health domain, examples include a comparison of surgical outcomes in patients with and without views of trees through their hospital room windows (Ulrich 1984); a comparison of women’s health in counties with and without tree loss resulting from emerald ash borer infestation (Donovan et al. 2015); a comparison of self-discipline in children living in public housing with and without nearby trees (Taylor et al. 2002); and a study of crime and stress in relation to the greening of neglected vacant lots, comparing blocks already treated with blocks not yet treated (Branas et al. 2011). In each instance, the strength of the study depends on the extent to which the two groups compared do not differ in ways other than the exposure of interest. Natural experiments have important advantages: they are opportunities to study realistic exposures in realistic settings, they can study long-term outcomes more readily than true experiments, and they can be far less expensive than true experiments. They can yield powerful insights, as illustrated by John Snow’s classic study of water sources during the 1854 cholera epidemic in London (Snow 1855). However, natural experiments pose several challenges for researchers. Practically, they require a nimble and rapid response once a study opportunity is recognized, often exceeding the capacity of funders, ethics committees, and other institutional structures. The more thorny challenge is conceptual: natural experiments are highly susceptible to bias, that is to say, to the tendency for exposure to vary across a study population by factors that are also associated with outcomes (Craig et al. 2012; Rutter 2007). Confounding and reverse causation can be difficult to exclude. For example, if people who walk in natural settings evince lower levels of stress than those who do not, is that because the nature contact has a salutary effect, or is it because people who are better at managing their stress choose to take more nature walks?

Finally, retrospective observational studies comprise the bulk of the literature on nature contact and health. Examples include the many recent studies of various health outcomes according to the greenness of residential neighborhoods. These studies have several advantages. They are practical. They can be conducted more rapidly than prospective studies. They can readily address long-term health outcomes. By using data collected for other purposes, they reduce costs. However, they also face the considerable challenges of controlling bias and confounding as well as the potential limits of data not designed specifically for testing nature–health hypotheses.

Directions for Future Research

Potential enhancements in epidemiologic research on the nature–health connection include innovative data sources, more diverse study settings, improved exposure assessment (discussed above), innovative outcome measures, and improved analytical approaches.

With respect to data sources, one option is tapping into large, ongoing cohort studies. For example, a recent analysis of the Nurses’ Health Study (NHS) examined the association between residential greenness and causes of death (James et al. 2016). This analysis benefited from the well-established, high-quality exposure and outcome data in an ongoing study. A related option is adding measures of nature contact to ongoing studies. For instance, both the Behavioral Risk Factor Surveillance System (BRFSS) and the National Health Interview Survey (NHIS) inquire about physical activity, but until now, neither has inquired about whether that activity takes place outdoors.

Improved computing capabilities offer the possibility of acquiring and analyzing “big data” from innovative sources. Examples include administrative data from health care systems (Birkhead et al. 2015; Mazzali and Duca 2015), mobile health data (Chen et al. 2012; Hayden 2016), environmental sources such as Google Street View and webcams (Schootman et al. 2016), and social media sources such as Twitter (Hamad et al. 2016). For instance, with smartphone apps such as Mappiness ( http://www.mappiness.org.uk/), Track Your Happiness ( https://www.trackyourhappiness.org/), and Urban Mind ( https://www.urbanmind.info/), users record their emotions. These responses are geolocated, permitting the study of minute-to-minute associations between proximity to nature and emotional states. The same is true for disease-specific apps such as Share the Journey, developed to study breast cancer ( http://sharethejourneyapp.org/).

With regard to study settings, most studies of nature contact and health have been carried out in cool, temperate climates, generally in high-income countries. Relatively little research has evaluated desert, mountainous, or shoreline landscapes—places where major population centers are located. Similarly, little research has been based in low- and middle-income settings, with their distinct profiles of environmental conditions and health vulnerabilities. Epidemiologic research in such settings will extend knowledge considerably.

Innovative outcome measures offer great promise when applied to health research on nature exposure (Haluza et al. 2014). These measures include stress indicators such as cortisol, amylase, and skin conductance (Beil and Hanes 2013; Jiang et al. 2014; JJ Roe et al. 2013); measures of brain activity including novel EEG methods (Aspinall et al. 2015; J Roe et al. 2013; Tilley et al. 2017) and functional brain imaging (Bratman et al. 2015b); genetic markers such as leukocyte basal gene expression profiles (Fredrickson et al. 2013); and telomere shortening (Woo et al. 2009). The use of physiological measurements may help elucidate mechanisms of action, as discussed above.

Finally, because nature contact invariably operates as part of a complex web of health determinants, statistical analysis must address this complexity. Analytical techniques including multilevel analysis (Diez-Roux 2000), complex causal process diagrams (Joffe and Mindell 2006), path analysis and structural equations, and the use of counterfactuals (Berzuini et al. 2012; Pearl 2009; Pearl et al. 2016) may all be useful in controlling bias and confounding; in disentangling multivariate, multilevel, bidirectional associations; and in clarifying causal pathways.

Advancing epidemiologic research requires both the improved methods described above as well as confirmation and clarification of specific associations. Figure 2 (based on Shanahan et al. 2015b) shows a model for this research. In this figure, a natural element such as tree canopy is identified and associated with defined functions (such as casting a shadow) that have direct or indirect effects on people (such as reducing UV radiation exposure) that in turn affect health (such as reducing skin cancer risk). The association between ecosystem functions and human effects may be subject to mediation and effect modification by a range of factors; these are encompassed by the term “moderating factors” in Figure 2.

Of the innumerable potential associations between nature contact and health, which are the most important to study? Although priorities will vary from setting to setting, the most common exposures (for example, urban greenspace, given the preponderance of people who live in cities) and the most common and/or high-consequence outcomes (such as conditions that account for a high burden of suffering) should be research priorities. Research should also focus on characterizing associations in ways that are relevant to practice, such as by defining dose–response relationships. Additionally, as discussed below, research should focus on subpopulations at particular risk or on those that could benefit disproportionately from nature contact, such as children, the elderly, and deprived groups.

Proposed research priorities

3.1

How is nature contact associated with specific health outcomes of public health importance, such as cardiovascular disease, cancer, depression, anxiety, well-being, and happiness?

3.a	How do these associations vary across different populations, life stages, and other factors?
3.b	Which forms of nature contact are most beneficial?

3.2

What “dose” and duration of exposure are needed to yield a benefit? How long does the beneficial effect last? Can habituation occur, with attenuated benefit over time?

3.3

If people born and raised in one setting relocate to a setting with different natural features, do the benefits of nature contact still operate?

3.4

Are there particular benefits from contact with landscapes or ecosystems that align with human evolutionary origins and/or with conservation priorities?

3.5

What are the adverse effects, if any, of nature contact?

Domain 4: Diversity and Equity—The Role of Nature Contact

At least four major strands of research are needed with respect to diversity and equity: a) patterns of disproportionate exposure; b) cultural and contextual factors that affect nature preferences and the experience of nature; c) differing patterns of benefit across different populations; and d) the possibility that improved access to nature may have unintended negative consequences on vulnerable populations.

With respect to disparities in access to nature, there is considerable evidence that disadvantaged urban populations are relatively deprived of access to nature and greenspace (Astell-Burt et al. 2014b; Boone et al. 2009; Dahmann et al. 2010; Heynen et al. 2006; Jennings and Gaither 2015; Jennings et al. 2016; Li et al. 2016; Pedlowski et al. 2002; Schwarz et al. 2015; Wolch et al. 2014). Much of this research centers on park access in urban settings. In some circumstances, studies have shown disadvantaged populations to have equal or greater proximity to parks and tree canopy (Barbosa et al. 2007; Cutts et al. 2009; Rigolon 2016; Schwarz et al. 2015; Vaughan et al. 2013; Wen et al. 2013), but typically in these situations, the quality of the parks, the level of programming, and/or park access remain significant barriers to park use.

There is also evidence that nature preferences vary across ethnic, cultural, and racial backgrounds. Tragically, the legacy of forced labor, lynchings, and other violence may evoke deeply disturbing associations with trees, fields, and forests among some African Americans (Johnson et al. 1997; Johnson and Bowker 2004). Diverse populations also express diverse preferences with respect to greenspace: a baseball diamond for some, a soccer field for others, picnic facilities for still others (Gobster 2002; Ho et al. 2005; Payne et al. 2002; Smiley et al. 2016). Similarly, the preferred forms of nature contact may vary: a group activity for some, solitary hikes for others. Such differences are deeply rooted in historical and geographic context (Buijs et al. 2009; Byrne and Wolch 2009). Livelihood may play an important role: a rural farmer likely has quite different preferences regarding nature from those of an urban computer programmer. These cultural and other filters may help determine whether, and how, nature contact confers health benefits. (There are limits to this approach: people may not fully recognize and report their own preferences, and attention restoration or other mechanisms could operate independently of preference or even awareness.) Research is needed to clarify the origin and durability of such preferences and their effects on health benefits. In practical terms, research on how best to engage communities in planning parks and greenspace will likely yield the best-performing facilities in terms of park use, health, and well-being.

There is evidence that contact with nature and greenspace may disproportionately benefit disadvantaged populations, attenuating the toxic effects of poverty and reducing health disparities—the so-called “equigenic” effect (Lachowycz and Jones 2014; Maas et al. 2006; Mitchell and Popham 2007, 2008; Mitchell et al. 2015). This effect needs to be confirmed and clarified in different settings, using a variety of study designs. If nature contact can help mitigate the toxic effects of poverty, this information could help guide interventions both to achieve both social justice goals and to realize the greatest return on investment in terms of human well-being.

Finally, improvements in access to greenspace may lead to “green gentrification,” an increase in property values that displaces low-income residents from their neighborhoods (Anguelovski 2017; Lewis and Gould 2017; Miller 2016; Wolch et al. 2014). This process needs to be studied and understood so that its adverse effects can be prevented.

Research on these dimensions of equity with respect to nature contact will permit both understanding the interplay of social disadvantage and nature contact and designing and targeting the most effective strategies for improving health and well-being for all (Rutt and Gulsrud 2016; Smiley et al. 2016).

Potential research priorities

4.1	How does access to nature vary by socioeconomic status, ethnicity, cultural background, and other social factors, in specific settings?
4.2	How do preferences and perceptions of nature vary by socioeconomic status, ethnicity, and other demographic factors, in specific settings, and how do these differences affect choices regarding time in nature?
4.3	What are the obstacles, both subjective and objective, to increasing the frequency of nature contact for disadvantaged communities?
4.4	How do the benefits of nature contact vary by socioeconomic status, ethnicity, and other demographic factors, in specific settings?
4.5	What unintended negative consequences flow from “green gentrification,” and what policies and practices help avoid those consequences?

Domain 5: Technological Nature

Modern information and communication technology that leverages digital computation is becoming exponentially more sophisticated and pervasive and may profoundly alter the human relationship with nature (Kahn 2011; Kurzweil 2005). Increasing use of technology—as exemplified by growing “screen time,” particularly among children—can compete with such activities as play in natural settings (Radesky and Christakis 2016; Vanderloo 2014) enough to have prompted the American Academy of Pediatrics to recommend limits on children’s screen time (Council on Communications and Media 2016).

However, technology does not only interfere with nature contact. “Technological nature” refers to technologies that mediate, simulate, promote, and/or augment the human experience of nature (Kahn 2011). Examples include real-time digital screen representations of local nature (digital nature “windows”), robot pets, and tele-robot-operated gardens. Virtual reality applications may simulate nature-based experiences (Guttentag 2010; Schutte et al. 2017), and the Pokémon Go game, during a peak in popularity in 2016, may have triggered outdoor activity (although the quality of the resulting nature interaction is unknown) (Althoff et al. 2016; Dorward et al. 2017; Howe et al. 2016). Other smartphone apps may facilitate or inform a connection with nature; examples include apps that assist with identifying trees, birds, or constellations.

Studies of people interacting with technological nature have begun to suggest that such interaction is better for people than no exposure to nature, but not as beneficial as genuine nature exposure (Kahn Jr et al. 2008; Kahn 2011; Melson et al. 2009). However, whether this initial trend generalizes across a wide range of human metrics, and if so, whether it will persist with increasing fidelity of technological nature, remain open questions. Research could also focus on the ways in which technological nature could broaden and even change the human experience of nature. One near-future example is linking apps with networked artificial intelligence conversational systems. Virtual reality is also a near-future pervasive form of interaction in social media and beyond, including in contact with the natural world (Guttentag 2010). Because of the growing role of technology in human–nature interactions, it is important to understand how best to harness technology to maximize health benefits.

Technological nature may be useful in another way: laboratory-based controlled experiments utilizing technology may help tease apart which aspects of the nature experience have which effects on people and how these effects are moderated according to individual differences. Here again, attention would need to be paid to how the technological nature experience compares to the actual nature experience.

Proposed research priorities

5.1	How can specific forms of technological nature increase and deepen the human experience of nature?
5.2	Where, how, and why does technological nature fall short in conferring human benefits relative to the actual experience of nature?
5.3	What forms of technological nature contact provide health benefits, and what are those benefits?
5.4	How do these findings vary by technology, context, and across age groups and other demographic factors?
5.5	What insights can virtual nature contact provide into the causal mechanisms of psychological benefits, and how ecologically valid will these insights be?

Domain 6: Economic and Policy Studies, Including Cobenefits

The benefits of nature contact need to be studied and tested not only as scientific hypotheses but also as policy propositions; this requires quantitative estimates of the value of these benefits. The principal intellectual framework for this approach comes from the field of ecological economics (Costanza 2015; Farley and Daly 2011; Stagl and Common 2005), and more particularly from the analysis and valuation of ecosystem services (Hester and Harrison 2010; Ninan and Costanza 2014; Ruckelshaus et al. 2015). Both civil society (Harnik and Welle 2009; NRPA 2015) and academic researchers (Naidoo et al. 2006; Roy et al. 2012; Shoup 2010) characterize the ecosystem services provided by parks and greenspace, tree canopy, open land, and other natural assets. However, these analyses generally focus on biophysical processes such as storm water management, air quality, and erosion control, omitting explicit consideration of human health and well-being. Key reports often fail even to mention human health, much less to quantify it as an ecosystem service (Fisher et al. 2009; Posner et al. 2016; Seppelt et al. 2011)—an omission that is likely to lead to incorrect conclusions and suboptimal policies.

Fortunately, recent publications have begun to integrate human health into ecosystem services analyses (Bayles et al. 2016; Breslow et al. 2016; Ford et al. 2015; Lindgren and Elmqvist 2017; Salmond et al. 2016; Sandifer et al. 2015; Willis and Petrokofsky 2017) and even to propose quantitative metrics (Jackson et al. 2013; Smith et al. 2013). In some cases, research identifies and quantifies the health cobenefits of green infrastructure and/or conservation efforts, providing a more complete picture than would otherwise be available (Coutts and Hahn 2015; Larsen et al. 2012; Wolf and Robbins 2015). Health economics research can help value both health gains and relatively intangible benefits such as aesthetic enjoyment and happiness, as well as help quantify avoided health care costs, attributable to nature contact. Although precise estimates may be elusive and uncertainty must be acknowledged, in many cases, health benefits will be large enough to rival other ecosystem services in value. Importantly, this work needs to take a life course approach; although average medical costs during childhood are low, investments in nature contact early in life may yield substantial health improvements, and avoided medical costs, later in life (Wolf et al. 2015). Moreover, analysis needs to account for disbenefits of nature contact, such as allergic reactions and excessive sunlight exposure. Much more research and analysis are needed to address these issues.

Cost–benefit analyses need to estimate how much benefit will flow from specific kinds of investments in nature contact and to make comparisons among policy alternatives, a key consideration for city officials, park managers, and other decision makers confronting the reality of limited resources (Ruckelshaus et al. 2015). This research requires mechanistic models that can predict a mix of monetary and nonmonetary ecosystem services. Teams of scientists and policy makers need to be highly multidisciplinary to perform “full benefit accounting” that considers both health benefits and nonhealth benefits (ranging from storm water management to biodiversity protection to enhanced property value) of nature’s services.

As noted above, policy research needs to include a strong focus on equity issues—from documenting disparities in nature access to testing solutions to preventing gentrification and other unintended consequences of interventions.

Proposed research priorities

6.1

What are the best methods for valuing the health benefits of nature?

6.2

What is the health-related value of various forms of nature contact?

6.2a	Cost–benefit analyses
6.2b	Cost-effectiveness analyses
6.2c	Long-term analyses across the life span
6.2d	Integration with other ecosystem services assessments

6.3

What are the optimal methods of combining both health and nonhealth cobenefits of various forms of nature contact?

Domain 7: Implementation Science—Studies of What Works

Research findings do not necessarily translate into action. According to one leading researcher, “[d]issemination and implementation of research findings into practice are necessary to achieve a return on investment in our research enterprise and to apply research findings to improve outcomes in the broader community” (Colditz 2012). This is the motivation for implementation science—research that “supports movement of evidence-based effective health care and prevention strategies or programs from the clinical or public health knowledge base into routine use” (Colditz 2012). Although descriptive studies can identify and quantify health benefits of nature contact, intervention studies are needed to determine what works in practice (Kondo et al. 2015).

Like translational research in medicine, designed to bring research findings “from the bench to the bedside” to improve patient outcomes, studies of the nature–health association can be designed with real-world application in mind. Such studies might be structured as true experiments, consistent with clinical trials used routinely in biomedical research. They might also take the form of program evaluations following a wide range of interventions. Integrated quantitative and qualitative research may provide the most comprehensive understanding of health impacts, from individual to community scales. Important products of such work are predictive models and decision tools for use by planners and decision makers. For example, some cities use tools such as the U.S. Forest Service’s i-Tree software ( http://www.itreetools.org/) to analyze environmental services associated with tree planting. Might further development of such tools incorporate additional mental and physical health benefits?

Proposed research priorities

(Examples only; research topics in this domain will vary by particular circumstances)

7.1

With respect to specific interventions designed to promote health and well-being through nature contact, how are they implemented (legal and administrative arrangements, partnerships, costs, and financial mechanisms), and how do they work (in terms of attracting people and yielding desired outcomes)? Examples of potential high-impact research include the following:

7.1a	Which trail and park designs perform best in promoting physical activity (Qviström 2016)?
7.1b	How should children’s play spaces be designed to optimize nature contact (Gundersen et al. 2016)?
7.1c	Which configurations of children’s outdoor schools optimize health, social relationships, and learning (Roe and Aspinall 2011; Söderström et al. 2013)?
7.1d	Which design features in natural settings (such as sweeping views, known as “prospect,” and safe places to hide, known as “refuge”) make them most restorative (Gatersleben and Andrews 2013)?
7.1e	What dose of nature is needed to optimize benefits (Hunter and Askarinejad 2015; Shanahan et al. 2015a, 2016)? How is that dose most effectively delivered? Are programs such as Park Prescriptions, in which health care providers direct their patients to spend time in natural settings, effective (Coffey and Gauderer 2016)?
7.1f	Which outdoor programs most effectively treat post-traumatic stress disorder in veterans (Poulsen et al. 2015)?
7.1g	What is the efficacy of horticultural therapy in treating dementia, anxiety, stress, and other conditions in the institutionalized and noninstitutionalized elderly (Detweiler et al. 2012)?

Conclusions

According to the best available evidence, nature contact offers considerable promise in addressing a range of health challenges, including many, such as obesity, cardiovascular disease, depression, and anxiety, that are public health priorities. Nature contact offers promise both as prevention and as treatment across the life course. Potential advantages include low costs relative to conventional medical interventions, safety, practicality, not requiring dispensing by highly trained professionals, and multiple cobenefits. Few medications can boast these attributes.

However, many questions regarding the health benefits of nature contact remain unanswered. A robust program of scientific research is needed to generate evidence-based answers to these questions. This paper has identified seven domains of research that, together, frame an agenda for needed research: mechanistic biomedical studies, exposure science, epidemiologic studies, studies focusing on diversity and equity, studies of technological nature, economic and policy studies, and implementation science. Although particular challenges exist in such areas as exposure assessment, innovative data sources and analytical techniques represent exciting opportunities. The results of such research will guide interventions across a wide range of settings, populations, spatial scales, and forms of nature. Health professionals, ecologists, landscape architects, parks staff, educators, and many others will in turn be able to apply these results to improve health and well-being on a large scale.

Acknowledgments

This research agenda was facilitated by the Center for Creative Conservation at the University of Washington, which receives partial support from REI. Support for K.L.W. was provided by the Pacific Northwest Research Station, U.S. Department of Agriculture Forest Service. Support for G.N.B. was provided by the Wallenberg Foundation.

References

Akpinar A, Barbosa-Leiker C, Brooks KR. 2016. Does green space matter? Exploring relationships between green space type and health indicators. Urb Forestry Urb Greening 20:407–418, doi:10.1016/j.ufug.2016.10.013. Crossref, Google Scholar
Althoff T, White RW, Horvitz E. 2016. Influence of Pokémon Go on physical activity: Study and implications. J Med Internet Res 18:e315, PMID: 27923778, doi:10.2196/jmir.6759. Crossref, Medline, Google Scholar
Alvey AA. 2006. Promoting and preserving biodiversity in the urban forest. Urb Forestry Urb Greening 5:195–201, doi:10.1016/j.ufug.2006.09.003. Crossref, Google Scholar
Ambrey CL, Cartlidge N. 2017. Do the psychological benefits of greenspace depend on one's personality?. Pers Individ Dif 116:233–239, doi:10.1016/j.paid.2017.05.001. Crossref, Google Scholar
Ambrey CL. 2016. An investigation into the synergistic wellbeing benefits of greenspace and physical activity: moving beyond the mean. Urb Forestry Urb Greening 19:7–12, doi:10.1016/j.ufug.2016.06.020. Crossref, Google Scholar
Amoly E, Dadvand P, Forns J, Lopez-Vicente M, Basagana X, Julvez J, et al.2014. Green and blue spaces and behavioral development in Barcelona schoolchildren: The BREATHE project. Environ Health Perspect 122(12):1351–1358, PMID: 25204008, doi:10.1289/ehp.1408215. Link, Google Scholar
Andrusaityte S, Grazuleviciene R, Kudzyte J, Bernotiene A, Dedele A, Nieuwenhuijsen MJ. 2016. Associations between neighbourhood greenness and asthma in preschool children in Kaunas, Lithuania: a case–control study. BMJ Open 6(4):e010341, PMID: 27067890, doi:10.1136/bmjopen-2015-010341. Crossref, Medline, Google Scholar
Anguelovski I. 2017. Urban greening as the ultimate urban environmental justice tragedy?. Planning Theory 16(1):NP2–NP23, doi:10.1177/1473095216654448. Crossref, Google Scholar
Armstrong BK, Saracci R, White E. 2008. Principles of Exposure Measurement in Epidemiology: Collecting, Evaluating, and Improving Measures of Disease Risk Factors. 2nd ed. Oxford, UK:Oxford University Press. Google Scholar
Aspinall P, Mavros P, Coyne R, Roe J. 2015. The urban brain: analysing outdoor physical activity with mobile EEG. Br J Sports Med 49(4):272–276, PMID: 23467965, doi:10.1136/bjsports-2012-091877. Crossref, Medline, Google Scholar
Astell-Burt T, Feng X, Kolt GS. 2013. Does access to neighbourhood green space promote a healthy duration of sleep? Novel findings from a cross-sectional study of 259 319 Australians. BMJ Open 3(8):e003094, doi:10.1136/bmjopen-2013-003094. Crossref, Medline, Google Scholar
Astell-Burt T, Feng X, Kolt GS. 2014a. Is neighborhood green space associated with a lower risk of type 2 diabetes? Evidence from 267,072 Australians. Diabetes Care 37:197–201, PMID: 24026544, doi:10.2337/dc13-1325. Crossref, Medline, Google Scholar
Astell-Burt T, Feng X, Mavoa S, Badland HM, Giles-Corti B. 2014b. Do low-income neighbourhoods have the least green space? a cross-sectional study of Australia's most populous cities. BMC Public Health 14:292, PMID: 24678610, doi:10.1186/1471-2458-14-292. Crossref, Medline, Google Scholar
Astell-Burt T, Mitchell R, Hartig T. 2014c. The association between green space and mental health varies across the lifecourse. A longitudinal study. J Epidemiol Community Health 68:578–583, doi:10.1136/jech-2013-203767. Crossref, Medline, Google Scholar
Balseviciene B, Sinkariova L, Grazuleviciene R, Andrusaityte S, Uzdanaviciute I, Dedele A, et al.2014. Impact of residential greenness on preschool children’s emotional and behavioral problems. Int J Environ Res Public Health 11(7):6757–6770, PMID: 24978880, doi:10.3390/ijerph110706757. Crossref, Medline, Google Scholar
Bancroft C, Joshi S, Rundle A, Hutson M, Chong C, Weiss CC, et al.2015. Association of proximity and density of parks and objectively measured physical activity in the united states: a systematic review. Soc Sci Med 138:22–30, PMID: 26043433, doi:10.1016/j.socscimed.2015.05.034. Crossref, Medline, Google Scholar
Barbosa O, Tratalos JA, Armsworth PR, Davies RG, Fuller RA, Johnson P, et al.2007. Who benefits from access to green space? A case study from Sheffield, UK. Landscape and Urban Planning 83(2–3):187–195, doi:10.1016/j.landurbplan.2007.04.004. Crossref, Google Scholar
Barker SB, Wolen AR. 2008. The benefits of human-companion animal interaction: a review. J Vet Med Educ 35(4):487–495, PMID: 19228898, doi:10.3138/jvme.35.4.487. Crossref, Medline, Google Scholar
Barton J, Bragg R, Wood C, Pretty J, eds. 2016. Green Exercise: Linking Nature, Health and Well-Being. Abingdon, UK:Earthscan/Routledge. Crossref, Google Scholar
Bauman A, Merom D, Bull FC, Buchner DM, Fiatarone Singh MA. 2016. Updating the evidence for physical activity: Summative reviews of the epidemiological evidence, prevalence, and interventions to promote “active aging.”. Gerontologist 56(suppl2):S268–S280, doi:10.1093/geront/gnw031. Crossref, Medline, Google Scholar
Bayles BR, Brauman KA, Adkins JN, Allan BF, Ellis Am, Goldberg TL, et al.2016. Ecosystem services connect environmental change to human health outcomes. EcoHealth 13(3):443–449, PMID: 27357081, doi:10.1007/s10393-016-1137-5. Crossref, Medline, Google Scholar
Beaudreau AH, Levin PS, Norman KC. 2011. Using folk taxonomies to understand stakeholder perceptions for species conservation. Conserv Lett 4(6):451–463, doi:10.1111/j.1755-263X.2011.00199.x. Crossref, Google Scholar
Beil K, Hanes D. 2013. The influence of urban natural and built environments on physiological and psychological measures of stress- a pilot study. Int J Environ Res Public Health 10(4):1250–1267, PMID: 23531491, doi:10.3390/ijerph10041250. Crossref, Medline, Google Scholar
Bell JF, Wilson JS, Liu GC. 2008. Neighborhood greenness and 2-year changes in body mass index of children and youth. Am J Prev Med 35(6):547–553, PMID: 19000844, doi:10.1016/j.amepre.2008.07.006. Crossref, Medline, Google Scholar
Ben-Joseph E, Lee JS, Cromley EK, Laden F, Troped PJ. 2013. Virtual and actual: Relative accuracy of on-site and web-based instruments in auditing the environment for physical activity. Health Place 19:138–150, PMID: 23247423, doi:10.1016/j.healthplace.2012.11.001. Crossref, Medline, Google Scholar
Berland A, Shiflett SA, Shuster WD, Garmestani AS, Goddard HC, Herrmann DL, et al.2017. The role of trees in urban stormwater management. Landsc Urban Plan 162:167–177, doi:10.1016/j.landurbplan.2017.02.017. Crossref, Medline, Google Scholar
Berto R. 2014. The role of nature in coping with psycho-physiological stress: A literature review on restorativeness. Behav Sci (Basel) 4(4):394–409, doi:10.3390/bs4040394. Crossref, Medline, Google Scholar
Berzuini C, Dawid P, Bernardinelli L, Berzuini C. 2012. Causality: Statistical Perspectives and Applications. Hoboken, NJ:Wiley. Crossref, Google Scholar
Beyer KMM, Kaltenbach A, Szabo A, Bogar S, Nieto FJ, Malecki KM. 2014. Exposure to neighborhood green space and mental health: Evidence from the survey of the health of Wisconsin. Int J Environ Res Public Health 11(3):3453–3472, doi:10.3390/ijerph110303453. Crossref, Medline, Google Scholar
Bijker RA, Sijtsma FJ. 2017. A portfolio of natural places: using a participatory GIS tool to compare the appreciation and use of green spaces inside and outside urban areas by urban residents. Landsc Urban Plan 158:155–165, doi:10.1016/j.landurbplan.2016.10.004. Crossref, Google Scholar
Bingham DD, Costa S, Hinkley T, Shire KA, Clemes SA, Barber SE. 2016. Physical activity during the early years: a systematic review of correlates and determinants. Am J Prev Med 51(3):384–402, PMID: 27378255, doi:10.1016/j.amepre.2016.04.022. Crossref, Medline, Google Scholar
Birkhead GS, Klompas M, Shah NR. 2015. Uses of electronic health records for public health surveillance to advance public health. Annu Rev Public Health 36:345–359, PMID: 25581157, doi:10.1146/annurev-publhealth-031914-122747. Crossref, Medline, Google Scholar
Blumenthal DS, Diclemente RJ, Braithwaite R, Smith SA. 2013. Community-Based Participatory Health Research: Issues, Methods, and Translation to Practice. 2nd ed. New York, NY:Springer. Google Scholar
Bodicoat DH, O'Donovan G, Dalton AM, Gray LJ, Yates T, Edwardson C, et al.2014. The association between neighbourhood greenspace and type 2 diabetes in a large cross-sectional study. BMJ Open 4:e006076, doi:10.1136/bmjopen-2014-006076. Crossref, Medline, Google Scholar
Bogar S, Beyer KM. 2016. Green space, violence, and crime. Trauma Violence Abuse 17(2):160–171, PMID: 25824659, doi:10.1177/1524838015576412. Crossref, Medline, Google Scholar
Bolund P, Hunhammar S. 1999. Ecosystem services in urban areas. Ecol Econ 29(2):293–301, doi:10.1016/S0921-8009(99)00013-0. Crossref, Google Scholar
Boone CG, Buckley GL, Grove JM, Sister C. 2009. Parks and people: an environmental justice inquiry in Baltimore, Maryland. Ann Assoc Am Geogr 99(4):767–787, doi:10.1080/00045600903102949. Crossref, Google Scholar
Bowler DE, Buyung-Ali L, Knight TM, Pullin AS. 2010. Urban greening to cool towns and cities: a systematic review of the empirical evidence. Landsc Urban Plan 97:147–155, doi:10.1016/j.landurbplan.2010.05.006. Crossref, Google Scholar
Bowler DE, Buyung-Ali LM, Knight TM, Pullin AS. 2010. A systematic review of evidence for the added benefits to health of exposure to natural environments. BMC Public Health 10:456, PMID: 20684754, doi:10.1186/1471-2458-10-456. Crossref, Medline, Google Scholar
Branas CC, Cheney RA, MacDonald JM, Tam VW, Jackson TD, Ten Have TR. 2011. A difference-in-differences analysis of health, safety, and greening vacant urban space. Am J Epidemiol 174(11):1296–1306, PMID: 22079788, doi:10.1093/aje/kwr273. Crossref, Medline, Google Scholar
Bratman GN, Daily GC, Levy BJ, Gross JJ. 2015a. The benefits of nature experience: improved affect and cognition. Landsc Urban Plan 138:41–50, doi:10.1016/j.landurbplan.2015.02.005. Crossref, Google Scholar
Bratman GN, Hamilton JP, Daily GC. 2012. The impacts of nature experience on human cognitive function and mental health. Ann N Y Acad Sci 1249:118–136, PMID: 22320203, doi:10.1111/j.1749-6632.2011.06400.x. Crossref, Medline, Google Scholar
Bratman GN, Hamilton JP, Hahn KS, Daily GC, Gross JJ. 2015b. Nature experience reduces rumination and subgenual prefrontal cortex activation. Proc Natl Acad Sci USA 112(28):8567–8572. Crossref, Medline, Google Scholar
Breslow SJ, Sojka B, Barnea R, Basurto X, Carothers C, Charnley S, et al.2016. Conceptualizing and operationalizing human wellbeing for ecosystem assessment and management. Environ Sci Policy 66:250–259, doi:10.1016/j.envsci.2016.06.023. Crossref, Google Scholar
Brown SC, Lombard J, Wang K, Byrne MM, Toro M, Plater-Zyberk E, et al.2016. Neighborhood greenness and chronic health conditions in medicare beneficiaries. Am J Prev Med 51(1):78–89, PMID: 27061891, doi:10.1016/j.amepre.2016.02.008. Crossref, Medline, Google Scholar
Broyles ST, Mowen AJ, Theall KP, Gustat J, Rung AL. 2011. Integrating social capital into a park-use and active-living framework. Am J Prev Med 40(5):522–529, PMID: 21496751, doi:10.1016/j.amepre.2010.12.028. Crossref, Medline, Google Scholar
Brunson L, Kuo FE, Sullivan WC. 2001. Resident appropriation of defensible space in public housing: implications for safety and community. Environ Behav 33(5):626–652, doi:10.1177/00139160121973160. Crossref, Google Scholar
Buijs AE, Elands BHM, Langers F. 2009. No wilderness for immigrants: cultural differences in images of nature and landscape preferences. Landsc Urban Plan 91:113–123, doi:10.1016/j.landurbplan.2008.12.003. Crossref, Google Scholar
Byrne J, Wolch J. 2009. Nature, race, and parks: past research and future directions for geographic research. Prog Hum Geogr 33(6):743–765, doi:10.1177/0309132509103156. Crossref, Google Scholar
Calogiuri G, Chroni S. 2014. The impact of the natural environment on the promotion of active living: an integrative systematic review. BMC Public Health 14:873, PMID: 25150711, doi:10.1186/1471-2458-14-873. Crossref, Medline, Google Scholar
Cervinka R, Röderer K, Hefler E. 2012. Are nature lovers happy? On various indicators of well-being and connectedness with nature. J Health Psychol 17(3):379–388, PMID: 21859800, doi:10.1177/1359105311416873. Crossref, Medline, Google Scholar
Chaix B, Meline J, Duncan S, Merrien C, Karusisi N, Perchoux C, et al.2013. GPS tracking in neighborhood and health studies: a step forward for environmental exposure assessment, a step backward for causal inference?. Health Place 21:46–51, PMID: 23425661, doi:10.1016/j.healthplace.2013.01.003. Crossref, Medline, Google Scholar
Charreire H, Mackenbach JD, Ouasti M, Lakerveld J, Compernolle S, Ben-Rebah M, et al.2014. Using remote sensing to define environmental characteristics related to physical activity and dietary behaviours: a systematic review (The Spotlight Project). Health Place 25:1–9, PMID: 24211730, doi:10.1016/j.healthplace.2013.09.017. Crossref, Medline, Google Scholar
Chen C, Haddad D, Selsky J, Hoffman JE, Kravitz RL, Estrin DE, et al.2012. Making sense of mobile health data: an open architecture to improve individual- and population-level health. J Med Internet Res 14(4):e112, doi:10.2196/jmir.2152. Crossref, Medline, Google Scholar
Clarke P, Ailshire J, Melendez R, Bader M, Morenoff J. 2010. Using Google Earth to conduct a neighborhood audit: reliability of a virtual audit instrument. Health Place 16(6):1224–1229, PMID: 20797897, doi:10.1016/j.healthplace.2010.08.007. Crossref, Medline, Google Scholar
Cleland V, Crawford D, Baur LA, Hume C, Timperio A, Salmon J. 2008. A prospective examination of children's time spent outdoors, objectively measured physical activity and overweight. Int J ObesRelat Metab Disord 32:1685–1693, doi:10.1038/ijo.2008.171. Crossref, Google Scholar
Clements R. 2004. An investigation of the status of outdoor play. Contemp Iss Early Child 5(1):68–80, doi:10.2304/ciec.2004.5.1.10. Crossref, Google Scholar
Coffey JS, Gauderer L. 2016. When pediatric primary care providers prescribe nature engagement at a state park, do children “fill” the prescription?. Ecopsychology 8(4):207–214, doi:10.1089/eco.2016.0019. Crossref, Google Scholar
Cohen-Cline H, Turkheimer E, Duncan GE. 2015. Access to green space, physical activity and mental health: a twin study. J Epidemiol Community Health 69(6):523–529, PMID: 25631858, doi:10.1136/jech-2014-204667. Crossref, Medline, Google Scholar
Colditz GA. 2012. The promise and challenges of dissemination and implementation research. Dissemination and Implementation Research in Health: Translating Science into Practice. Brownson RC, Colditz GA, Proctor EK, eds. Oxford, UK:Oxford University Press, 3–22. Google Scholar
Collado S, Corraliza JA, Staats H, Ruiz M. 2015. Effect of frequency and mode of contact with nature on children's self-reported ecological behaviors. J Environ Psychol 41:65–73, doi:10.1016/j.jenvp.2014.11.001. Crossref, Google Scholar
Conniff A, Craig T. 2016. A methodological approach to understanding the wellbeing and restorative benefits associated with greenspace. Urban For Urban Green 19:103–109, doi:10.1016/j.ufug.2016.06.019. Crossref, Google Scholar
Coon JT, Boddy K, Stein K, Whear R, Barton J, Depledge MH. 2011. Does participating in physical activity in outdoor natural environments have a greater effect on physical and mental wellbeing than physical activity indoors? A systematic review. Environ Sci Technol 45(5):1761–1772, doi:10.1021/es102947t. Crossref, Medline, Google Scholar
Costanza R. 2015. An Introduction to Ecological Economics. 2nd ed. Boca Raton, FL:CRC Press. Google Scholar
Council on Communications and Media. 2016. Media use in school-aged children and adolescents. Pediatrics 138(5):e20162592. Google Scholar
Coutts C, Hahn M. 2015. Green infrastructure, ecosystem services, and human health. Int J Environ Res Public Health 12(8):9768–9798, PMID: 26295249, doi:10.3390/ijerph120809768. Crossref, Medline, Google Scholar
Coutts C, Horner M, Chapin T. 2010. Using geographical information system to model the effects of green space accessibility on mortality in florida. Geocarto Int 25(6):471–484, doi:10.1080/10106049.2010.505302. Crossref, Google Scholar
Cracknell D, White MP, Pahl S, Nichols WJ, Depledge MH. 2016. Marine biota and psychological well-being: A preliminary examination of dose–response effects in an aquarium setting. Environ Behav 48(10):1242–1269, doi:10.1177/0013916515597512. Crossref, Medline, Google Scholar
Craig P, Cooper C, Gunnell D, Haw S, Lawson K, Macintyre S, et al.2012. Using natural experiments to evaluate population health interventions: New Medical Research Council guidance. J Epidemiol Community Health 66(12):1182–1186, PMID: 22577181, doi:10.1136/jech-2011-200375. Crossref, Medline, Google Scholar
Cronon W. 1996. Uncommon Ground: Rethinking the Human Place in Nature. New York, NY:W.W. Norton & Co. Google Scholar
Cutts BB, Darby KJ, Boone CG, Brewis A. 2009. City structure, obesity, and environmental justice: an integrated analysis of physical and social barriers to walkable streets and park access. Soc Sci Med 69(9):1314–1322, doi:10.1016/j.socscimed.2009.08.020. Crossref, Medline, Google Scholar
Dadvand P, Villanueva CM, Font-Ribera L, Martinez D, Basagana X, Belmonte J, et al.2014a. Risks and benefits of green spaces for children: a cross-sectional study of associations with sedentary behavior, obesity, asthma, and allergy. Environ Health Perspect 122(12):1329–1335, PMID: 25157960, doi:10.1289/ehp.1308038. Link, Google Scholar
Dadvand P, Wright J, Martinez D, Basagaña X, McEachan RRC, Cirach M, et al.2014b. Inequality, green spaces, and pregnant women: roles of ethnicity and individual and neighbourhood socioeconomic status. Environ Int 71:101–108, doi:10.1016/j.envint.2014.06.010. Crossref, Medline, Google Scholar
Dadvand P, Bartoll X, Basagaña X, Dalmau-Bueno A, Martinez D, Ambros A, et al.2016. Green spaces and general health: roles of mental health status, social support, and physical activity. Environ Int 91:161–167, PMID: 26949869, doi:10.1016/j.envint.2016.02.029. Crossref, Medline, Google Scholar
Dahmann N, Wolch J, Joassart-Marcelli P, Reynolds K, Jerrett M. 2010. The active city? Disparities in provision of urban public recreation resources. Health Place 16(3):431–445, PMID: 20056472, doi:10.1016/j.healthplace.2009.11.005. Crossref, Medline, Google Scholar
Dallimer M, Irvine KN, Skinner AMJ, Davies ZG, Rouquette JR, Maltby LL, et al.2012. Biodiversity and the feel-good factor: understanding associations between self-reported human well-being and species richness. BioScience 62(1):47–55, doi:10.1525/bio.2012.62.1.9. Crossref, Google Scholar
Davies ZG, Edmondson JL, Heinemeyer A, Leake JR, Gaston KJ. 2011. Mapping an urban ecosystem service: Quantifying above-ground carbon storage at a city-wide scale. J Appl Ecol 48(5):1125–1134, doi:10.1111/j.1365-2664.2011.02021.x. Crossref, Google Scholar
de Bloom J, Sianoja M, Korpela K, Tuomisto M, Lilja A, Geurts S, et al.2017. Effects of park walks and relaxation exercises during lunch breaks on recovery from job stress: two randomized controlled trials. J Environ Psychol 51:14–30, doi:10.1016/j.jenvp.2017.03.006. Crossref, Google Scholar
de Vries S, van Dillen SM, Groenewegen PP, Spreeuwenberg P. 2013. Streetscape greenery and health: Stress, social cohesion and physical activity as mediators. Soc Sci Med 94:26–33, PMID: 23931942, doi:10.1016/j.socscimed.2013.06.030. Crossref, Medline, Google Scholar
de Vries S, Verheij RA, Groenewegen PP, Spreeuwenberg P. 2003. Natural environments—healthy environments? An exploratory analysis of the relationship between greenspace and health. Environ Plann A 35(10):1717–1731, doi:10.1068/a35111. Crossref, Google Scholar
Detweiler MB, Sharma T, Detweiler JG, Murphy PF, Lane S, Carman J, et al.2012. What is the evidence to support the use of therapeutic gardens for the elderly?. Psychiatry Investig 9(2):100–110, doi:10.4306/pi.2012.9.2.100. Crossref, Medline, Google Scholar
Diette GB, Lechtzin N, Haponik E, Devrotes A, Rubin HR. 2003. Distraction therapy with nature sights and sounds reduces pain during flexible bronchoscopy. Chest 123(3):941–948, doi:10.1378/chest.123.3.941. Crossref, Medline, Google Scholar
Diez-Roux AV. 2000. Multilevel analysis in public health research. Annu Rev Public Health 21:171–192, PMID: 10884951, doi:10.1146/annurev.publhealth.21.1.171. Crossref, Medline, Google Scholar
Donovan GH, Michael YL, Gatziolis D, Prestemon JP, Whitsel EA. 2015. Is tree loss associated with cardiovascular-disease risk in the Women's Health Initiative? A natural experiment. Health Place 36:1–7, PMID: 26335885, doi:10.1016/j.healthplace.2015.08.007. Crossref, Medline, Google Scholar
Dooris M. 2006. Healthy settings: Challenges to generating evidence of effectiveness. Health Promot Int 21(1):55–65, PMID: 16339774, doi:10.1093/heapro/dai030. Crossref, Medline, Google Scholar
Dorward LJ, Mittermeier JC, Sandbrook C, Spooner F. 2017. Pokémon Go: Benefits, costs, and lessons for the conservation movement. Conservation Letters 10(1):160–165, doi:10.1111/conl.12326. Crossref, Google Scholar
Duncan M, Clarke N, Birch S, Tallis J, Hankey J, Bryant E, et al.2014. The effect of green exercise on blood pressure, heart rate and mood state in primary school children. Int J Environ Res Public Health 11(4):3678–3688, doi:10.3390/ijerph110403678. Crossref, Medline, Google Scholar
Dunning T. 2012. Natural Experiments in the Social Sciences: A Design-Based Approach. Cambridge, UK:Cambridge University Press. Crossref, Google Scholar
Dzhambov AM, Dimitrova DD, Dimitrakova ED. 2014. Association between residential greenness and birth weight: Systematic review and meta-analysis. Urb Forestry Urb Greening 13(4):621–629, doi:10.1016/j.ufug.2014.09.004. Crossref, Google Scholar
Ekkel ED, de Vries S. 2017. Nearby green space and human health: Evaluating accessibility metrics. Landsc Urban Plan 157:214–220, doi:10.1016/j.landurbplan.2016.06.008. Crossref, Google Scholar
Evensen KH, Raanaas RK, Hagerhall CM, Johansson M, Patil GG. 2015. Restorative elements at the computer workstation: A comparison of live plants and inanimate objects with and without window view. . Environ Behav 47(3):288–303, doi:10.1177/0013916513499584. Crossref, Google Scholar
Faber Taylor A, Kuo F, Sullivan W. 2001. Coping with ADD: the surprising connection to green play settings. Environ Behav 33(1):54–77, doi:10.1177/00139160121972864. Crossref, Google Scholar
Faber Taylor A, Kuo F. 2009. Children with attention deficits concentrate better after walk in the park. J Atten Disord 12(5):402–409, doi:10.1177/1087054708323000. Crossref, Medline, Google Scholar
Faber Taylor A, Kuo FEM. 2011. Could exposure to everyday green spaces help treat ADHD? Evidence from children's play settings. Appl Psychol Health Well Being 3(3):281–303, doi:10.1111/j.1758-0854.2011.01052.x. Crossref, Google Scholar
Fan Y, Das KV, Chen Q. 2011. Neighborhood green, social support, physical activity, and stress: Assessing the cumulative impact. Health Place 17(6):1202–1211, PMID: 21920795, doi:10.1016/j.healthplace.2011.08.008. Crossref, Medline, Google Scholar
Farley JC, Daly HE. 2011. Ecological Economics: Principles and Applications. 2nd ed. Washington, DC:Island Press. Google Scholar
Feda DM, Seelbinder A, Baek S, Raja S, Yin L, Roemmich JN. 2015. Neighbourhood parks and reduction in stress among adolescents: Results from Buffalo, New York. Indoor Built Environ 24(5):631–639, doi:10.1177/1420326X14535791. Crossref, Google Scholar
Feld S. 2015. Acoustemology. Keywords in Sound. Novak D, Sakakeeny M, eds. Durham, NC:Duke University Press, 12–21. Crossref, Google Scholar
Fisher B, Turner RK, Morling P. 2009. Defining and classifying ecosystem services for decision making. Ecol Econ 68(3):643–653, doi:10.1016/j.ecolecon.2008.09.014. Crossref, Google Scholar
Fjørtoft I. 2001. The natural environment as a playground for children: the impact of outdoor play activities in pre-primary school children. Early Child Educ J 29(2):111–117, doi:10.1023/A:1012576913074. Crossref, Google Scholar
Fjørtoft I. 2004. Landscape as playscape: The effects of natural environments on children's play and motor development. Children Youth Environ 14(2):21–44. Crossref, Google Scholar
Fleming CM, Manning M, Ambrey CL. 2016. Crime, greenspace and life satisfaction: An evaluation of the New Zealand experience. Landsc Urban Plan 149:1–10, doi:10.1016/j.landurbplan.2015.12.014. Crossref, Google Scholar
Fletcher R. 2016. Connection with nature is an oxymoron: a political ecology of “nature-deficit disorder. J Environ Educ, doi:10.1080/00958964.2016.1139534. Crossref, Google Scholar
Ford AES, Graham H, White PCL. 2015. Integrating human and ecosystem health through ecosystem services frameworks. EcoHealth 12(4):660–671, PMID: 26403794, doi:10.1007/s10393-015-1041-4. Crossref, Medline, Google Scholar
Fraser SD, Lock K. 2011. Cycling for transport and public health: A systematic review of the effect of the environment on cycling. Eur J Public Health 21(6):738–743, PMID: 20929903, doi:10.1093/eurpub/ckq145. Crossref, Medline, Google Scholar
Fredrickson BL, Grewen KM, Coffey KA, Algoe SB, Firestine AM, Arevalo JM, et al.2013. A functional genomic perspective on human well-being. Proc Natl Acad Sci USA 110(33):13684–13689, PMID: 23898182, doi:10.1073/pnas.1305419110. Crossref, Medline, Google Scholar
French AN, Ashby RS, Morgan IG, Rose KA. 2013. Time outdoors and the prevention of myopia. Exp Eye Res 114:58–68, PMID: 23644222, doi:10.1016/j.exer.2013.04.018. Crossref, Medline, Google Scholar
Frost JL. 2010. A History of Children's Play and Play Environments: Toward a Contemporary Child-Saving Movement. New York, NY:Routledge. Crossref, Google Scholar
Frumkin H. 2013. The evidence of nature and the nature of evidence. Am J Prev Med 44(2):196–197, PMID: 23332341, doi:10.1016/j.amepre.2012.10.016. Crossref, Medline, Google Scholar
Fuertes E, Markevych I, von Berg A, Bauer CP, Berdel D, Koletzko S, et al.2014. Greenness and allergies: evidence of differential associations in two areas in Germany. J Epidemiol Community Health 68:787–790, doi:10.1136/jech-2014-203903. Crossref, Medline, Google Scholar
Fuertes E, Markevych I, Bowatte G, Gruzieva O, Gehring U, Becker A, et al.2016. Residential greenness is differentially associated with childhood allergic rhinitis and aeroallergen sensitization in seven birth cohorts. Allergy 71(10):1461–1471, PMID: 27087129, doi:10.1111/all.12915. Crossref, Medline, Google Scholar
Gascon M, Triguero-Mas M, Martinez D, Dadvand P, Forns J, Plasencia A, et al.2015. Mental health benefits of long-term exposure to residential green and blue spaces: a systematic review. Int J Environ Res Public Health 12(4):4354–4379, PMID: 25913182, doi:10.3390/ijerph120404354. Crossref, Medline, Google Scholar
Gascon M, Triguero-Mas M, Martínez D, Dadvand P, Rojas-Rueda D, Plasència A, et al.2016a. Normalized difference vegetation index (NDVI) as a marker of surrounding greenness in epidemiological studies: the case of Barcelona City. Urb Forestry Urb Greening 19:88–94. Crossref, Google Scholar
Gascon M, Triguero-Mas M, Martínez D, Dadvand P, Rojas-Rueda D, Plasència A, et al.2016b. Residential green spaces and mortality: a systematic review. Environ Int 86:60–67. Crossref, Medline, Google Scholar
Gatersleben B, Andrews M. 2013. When walking in nature is not restorative-the role of prospect and refuge. Health Place 20:91–101, PMID: 23399852, doi:10.1016/j.healthplace.2013.01.001. Crossref, Medline, Google Scholar
Gelkopf M, Hasson-Ohayon I, Bikman M, Kravetz S. 2013. Nature adventure rehabilitation for combat-related posttraumatic chronic stress disorder: A randomized control trial. Psychiatry Res 209(3):485–493, PMID: 23541513, doi:10.1016/j.psychres.2013.01.026. Crossref, Medline, Google Scholar
Gobster PH. 2002. Managing urban parks for a racially and ethnically diverse clientele. Leis Sci 24(2):143–159, doi:10.1080/01490400252900121. Crossref, Google Scholar
Gray C, Gibbons R, Larouche R, Sandseter EB, Bienenstock A, Brussoni M, et al.2015. What is the relationship between outdoor time and physical activity, sedentary behaviour, and physical fitness in children? A systematic review. Int J Environ Res Public Health 12(6):6455–6474, PMID: 26062039, doi:10.3390/ijerph120606455. Crossref, Medline, Google Scholar
Grazuleviciene R, Danileviciute A, Dedele A, Vencloviene J, Andrusaityte S, Uzdanaviciute I, et al.2015. Surrounding greenness, proximity to city parks and pregnancy outcomes in Kaunas Cohort Study. Int J Hyg Environ Health 218(3):358–365, PMID: 25757723, doi:10.1016/j.ijheh.2015.02.004. Crossref, Medline, Google Scholar
Grigsby-Toussaint DS, Turi KN, Krupa M, Williams NJ, Pandi-Perumal SR, Jean-Louis G. 2015. Sleep insufficiency and the natural environment: Results from the US Behavioral Risk Factor Surveillance System Survey. Prev Med 78:78–84, PMID: 26193624, doi:10.1016/j.ypmed.2015.07.011. Crossref, Medline, Google Scholar
Groenewegen PP, van den Berg AE, Maas J, Verheij RA, de Vries S. 2012. Is a green residential environment better for health? If so, why?. Ann Assoc Am Geogr 102(5):996–1003, doi:10.1080/00045608.2012.674899. Crossref, Google Scholar
Grote R, Samson R, Alonso R, Amorim JH, Cariñanos P, Churkina G, et al.2016. Functional traits of urban trees: air pollution mitigation potential. Front Ecol Environ 14(10):543–550, doi:10.1002/fee.1426. Crossref, Google Scholar
Gubbels JS, Kremers SPJ, Droomers M, Hoefnagels C, Stronks K, Hosman C, et al.2016. The impact of greenery on physical activity and mental health of adolescent and adult residents of deprived neighborhoods: a longitudinal study. Health Place 40:153–160, doi:10.1016/j.healthplace.2016.06.002. Crossref, Medline, Google Scholar
Guggenheim JA, Northstone K, McMahon G, Ness AR, Deere K, Mattocks C, et al.2012. Time outdoors and physical activity as predictors of incident myopia in childhood: A prospective cohort study. Invest Ophthalmol Vis Sci 53(6):2856–2865, PMID: 22491403, doi:10.1167/iovs.11-9091. Crossref, Medline, Google Scholar
Gundersen V, Skår M, O'Brien L, Wold LC, Follo G. 2016. Children and nearby nature: a nationwide parental survey from norway. Urban Forestry & Urban Greening 17:116–125, doi:10.1016/j.ufug.2016.04.002. Crossref, Google Scholar
Guttentag DA. 2010. Virtual reality: Applications and implications for tourism. Tour Manag 31(5):637–651, doi:10.1016/j.tourman.2009.07.003. Crossref, Google Scholar
Hall DM, Camilo GR, Tonietto RK, Ollerton J, Ahrné K, Arduser M, et al.2017. The city as a refuge for insect pollinators. Conserv Biol 31(1):24–29, PMID: 27624925, doi:10.1111/cobi.12840. Crossref, Medline, Google Scholar
Haluza D, Schönbauer R, Cervinka R. 2014. Green perspectives for public health: A narrative review on the physiological effects of experiencing outdoor nature. Int J Environ Res Public Health 11(5):5445–5461, PMID: 24852391, doi:10.3390/ijerph110505445. Crossref, Medline, Google Scholar
Hamad EO, Savundranayagam MY, Holmes JD, Kinsella EA, Johnson AM. 2016. Toward a mixed-methods research approach to content analysis in the digital age: The combined content-analysis model and its applications to health care twitter feeds. J Med Internet Res 18(3):e60, doi:10.2196/jmir.5391. Crossref, Medline, Google Scholar
Han J-W, Choi H, Jeon Y-H, Yoon C-H, Woo J-M, Kim W. 2016. The effects of forest therapy on coping with chronic widespread pain: Physiological and psychological differences between participants in a forest therapy program and a control group. Int J Environ Res Public Health 13(3):255, doi:10.3390/ijerph13030255. Crossref, Medline, Google Scholar
Han K-T. 2009. Influence of limitedly visible leafy indoor plants on the psychology, behavior, and health of students at a junior high school in Taiwan. Environ Behav 41(5):658–692, doi:10.1177/0013916508314476. Crossref, Google Scholar
Hanski I, von Hertzen L, Fyhrquist N, Koskinen K, Torppa K, Laatikainen T, et al.2012. Environmental biodiversity, human microbiota, and allergy are interrelated. Proc Natl Acad Sci USA U S A 109(21):8334–8339, PMID: 22566627, doi:10.1073/pnas.1205624109. Crossref, Medline, Google Scholar
Harnik P, Welle B. 2009. Measuring the economic value of a city park system. Trust for Public Land. http://cloud.tpl.org/pubs/ccpe-econvalueparks-rpt.pdf [accessed 5 July 2017]. Google Scholar
Hartig T, Mitchell R, de Vries S, Frumkin H. 2014. Nature and health. Annu Rev Public Health 35:207–228, PMID: 24387090, doi:10.1146/annurev-publhealth-032013-182443. Crossref, Medline, Google Scholar
Hayden EC. 2016. Mobile-phone health apps deliver data bounty. Nature 531(7595):422–423, doi:10.1038/531422a. Crossref, Medline, Google Scholar
He M, Xiang F, Zeng Y, Mai J, Chen Q, Zhang J, et al.2015. Effect of time spent outdoors at school on the development of myopia among children in china: A randomized clinical trial. JAMA 314(11):1142–1148, PMID: 26372583, doi:10.1001/jama.2015.10803. Crossref, Medline, Google Scholar
Herzog TR, Bryce AG. 2007. Mystery and preference in within-forest settings. Environ Behav 39(6):779–796, doi:10.1177/0013916506298796. Crossref, Google Scholar
Hester RE, Harrison RM. 2010. Ecosystem Services. Cambridge, UK: Royal Society of Chemistry. Google Scholar
Heynen N, Perkins HA, Roy P. 2006. The political ecology of uneven urban green space: The impact of political economy on race and ethnicity in producing environmental inequality in Milwaukee. Urban Affairs Review 42(1):3–25, doi:10.1177/1078087406290729. Crossref, Google Scholar
Hillsdon M, Panter J, Foster C, Jones A. 2006. The relationship between access and quality of urban green space with population physical activity. Public Health 120(12):1127– 1132, doi:10.1016/j.puhe.2006.10.007. Crossref, Medline, Google Scholar
Ho C-h, Sasidharan V, Elmendorf W, Willits FK, Graefe A, Godbey G. 2005. Gender and ethnic variations in urban park preferences, visitation, and perceived benefits. J Leis Res 37(3):281–306. Crossref, Google Scholar
Holtan MT, Dieterlen SL, Sullivan WC. 2015. Social life under cover: tree canopy and social capital in Baltimore, Maryland. Environment and Behavior 47(5):502–525, doi:10.1177/0013916513518064. Crossref, Google Scholar
Home R, Hunziker M, Bauer N. 2012. Psychosocial outcomes as motivations for visiting nearby urban green spaces. Leis Sci 34(4):350–365, doi:10.1080/01490400.2012.687644. Crossref, Google Scholar
Howe KB, Suharlim C, Ueda P, Howe D, Kawachi I, Rimm EB. 2016. Gotta catch’em all! Pokémon Go and physical activity among young adults: difference in differences study. BMJ 355:i6270. Crossref, Medline, Google Scholar
Hoyle H, Hitchmough J, Jorgensen A. 2017. All about the ‘wow factor’? The relationships between aesthetics, restorative effect and perceived biodiversity in designed urban planting. Landsc Urban Plan 164:109–123, doi:10.1016/j.landurbplan.2017.03.011. Crossref, Google Scholar
Hu R, Yan G, Mu X, Luo J. 2014. Indirect measurement of leaf area index on the basis of path length distribution. Remote Sens Environ 155:239–247, doi:10.1016/j.rse.2014.08.032. Crossref, Google Scholar
Hu Z, Liebens J, Rao KR. 2008. Linking stroke mortality with air pollution, income, and greenness in northwest florida: An ecological geographical study. Int J Health Geogr 7:20, PMID: 18452609, doi:10.1186/1476-072X-7-20. Crossref, Medline, Google Scholar
Huete A, Didan K, Miura T, Rodriguez EP, Gao X, Ferreira LG. 2002. Overview of the radiometric and biophysical performance of the MODIS vegetation indices. Remote Sens Environ 83(1–2):195–213, doi:10.1016/S0034-4257(02)00096-2. Crossref, Google Scholar
Hunter AJ, Luck GW. 2015. Defining and measuring the social-ecological quality of urban greenspace: a semi-systematic review. Urban Ecosyst 18(4):1139–1163, doi:10.1007/s11252-015-0456-6. Crossref, Google Scholar
Hunter MR, Askarinejad A. 2015. Designer’s approach for scene selection in tests of preference and restoration along a continuum of natural to manmade environments. Front Psychol 6:1228, PMID: 26347691, doi:10.3389/fpsyg.2015.01228. Crossref, Medline, Google Scholar
Hunter RF, Christian H, Veitch J, Astell-Burt T, Hipp JA, Schipperijn J. 2015. The impact of interventions to promote physical activity in urban green space: A systematic review and recommendations for future research. Soc Sci Med 124:246–256, PMID: 25462429, doi:10.1016/j.socscimed.2014.11.051. Crossref, Medline, Google Scholar
Irwin MR, Cole SW. 2011. Reciprocal regulation of the neural and innate immune systems. Nat Rev Immunol 11(9):625–632, PMID: 21818124, doi:10.1038/nri3042. Crossref, Medline, Google Scholar
Jackson LE, Daniel J, McCorkle B, Sears A, Bush KF. 2013. Linking ecosystem services and human health: The eco-health relationship browser. Int J Public Health 58(5):747–755, PMID: 23877533, doi:10.1007/s00038-013-0482-1. Crossref, Medline, Google Scholar
James P, Banay RF, Hart JE, Laden F. 2015. A review of the health benefits of greenness. Curr Epidemiol Rep 2(2):131–142, PMID: 26185745, doi:10.1007/s40471-015-0043-7. Crossref, Medline, Google Scholar
James P, Hart JE, Banay RF, Laden F. 2016. Exposure to greenness and mortality in a nationwide prospective cohort study of women. Environ Health Perspect 124(9): 1344–1352, PMID: 27074702, doi:10.1289/ehp.1510363. Link, Google Scholar
Jason L, Glenwick D. 2016. Handbook of Methodological Approaches to Community-Based Research: Qualitative, Quantitative, and Mixed Methods. New York, NY:Oxford University Press. Google Scholar
Jennings V, Gaither CJ. 2015. Approaching environmental health disparities and green spaces: an ecosystem services perspective. Int J Environ Res Public Health 12(2):1952–1968, PMID: 25674782, doi:10.3390/ijerph120201952. Crossref, Medline, Google Scholar
Jennings V, Larson L, Yun J. 2016. Advancing sustainability through urban green space: Cultural ecosystem services, equity, and social determinants of health. Int J Environ Res Public Health 13(2):196, PMID: 26861365, doi:10.3390/ijerph13020196. Crossref, Medline, Google Scholar
Jiang B, Chang C-Y, Sullivan WC. 2014. A dose of nature: Tree cover, stress reduction, and gender differences. Landsc Urban Plan 132:26–36, doi:10.1016/j.landurbplan.2014.08.005. Crossref, Google Scholar
Joffe M, Mindell J. 2006. Complex causal process diagrams for analyzing the health impacts of policy interventions. Am J Public Health 96(3):473–479, PMID: 16449586, doi:10.2105/AJPH.2005.063693. Crossref, Medline, Google Scholar
Johnson CY, Bowker JM. 2004. African-American wildland memories. Environ Ethics 26(1):57–75, doi:10.5840/enviroethics200426141. Crossref, Google Scholar
Johnson CY, Horan PM, Pepper W. 1997. Race, rural residence, and wildland visitation: Examining the influence of sociocultural meaning. Rural Sociology 62(1):89–110, doi:10.1111/j.1549-0831.1997.tb00646.x. Crossref, Google Scholar
Jonker MF, van Lenthe FJ, Donkers B, Mackenbach JP, Burdorf A. 2014. The effect of urban green on small-area (healthy) life expectancy. J Epidemiol Community Health 68(10):999–1002, PMID: 25053616, doi:10.1136/jech-2014-203847. Crossref, Medline, Google Scholar
Kaczynski A, Henderson K. 2007. Environmental correlates of physical activity: a review of evidence about parks and recreation. Leisure Sci 29(4):315–354, doi:10.1080/01490400701394865. Crossref, Google Scholar
Kahn PH, Friedman B, Gill B, Hagman J, Severson RL, Freier NG, et al.2008. A plasma display window?—The shifting baseline problem in a technologically mediated natural world. J Environ Psychol 28(2):192–199, doi:10.1016/j.jenvp.2007.10.008. Crossref, Google Scholar
Kahn PH. 2010. a nature language: an agenda to catalog, save, and recover patterns of human-nature interaction. Ecopsychology 2(2):59–66, doi:10.1089/eco.2009.0047. Crossref, Google Scholar
Kahn PH. 2011. Technological Nature: Adaptation and the Future of Human Life. Cambridge, MA:MIT Press. Crossref, Google Scholar
Kamioka H, Okada S, Tsutani K, Park H, Okuizumi H, Handa S, et al.2014. Effectiveness of animal-assisted therapy: A systematic review of randomized controlled trials. Complement Ther Med 22(2):371–390, PMID: 24731910, doi:10.1016/j.ctim.2013.12.016. Crossref, Medline, Google Scholar
Kaplan R, Kaplan S. 1989. The Experience of Nature: A Psychological Perspective. New York, NY:Cambridge University Press. Google Scholar
Kaplan S. 1995. The restorative benefits of nature: Toward an integrative framework. J Environ Psychol 15(3):169–182, doi:10.1016/0272-4944(95)90001-2. Crossref, Google Scholar
Kardan O, Gozdyra P, Misic B, Moola F, Palmer LJ, Paus T, et al.2015. Neighborhood greenspace and health in a large urban center. Sci Rep 5:11610, PMID: 26158911, doi:10.1038/srep11610. Crossref, Medline, Google Scholar
Kawachi I, Subramanian SV, Kim D, eds. 2008. Social Capital and Health. New York, NY: Springer. Crossref, Google Scholar
Kaźmierczak A. 2013. The contribution of local parks to neighbourhood social ties. Landscape and Urban Planning 109(1):31–44, doi:10.1016/j.landurbplan.2012.05.007. Crossref, Google Scholar
Kellert SR, Wilson EO. 1993. The Biophilia Hypothesis. Washington, DC:Island Press. Google Scholar
Kellert SR. 2005. Nature and childhood development. Building for Life: Designing and Understanding the Human-Nature Connection. Kellert SR, ed. Washington, DC:Island Press, 63–89. Google Scholar
Keltner D, Haidt J. 2003. Approaching awe, a moral, spiritual, and aesthetic emotion. Cogn Emot 17(2):297–314, doi:10.1080/02699930302297. Crossref, Medline, Google Scholar
Kemperman A, Timmermans H. 2014. Green spaces in the direct living environment and social contacts of the aging population. Landsc Urban Plan 129:44–54, doi:10.1016/j.landurbplan.2014.05.003. Crossref, Google Scholar
Keniger LE, Gaston KJ, Irvine KN, Fuller RA. 2013. What are the benefits of interacting with nature?. Int J Environ Res Public Health 10(3):913–935, PMID: 23466828, doi:10.3390/ijerph10030913. Crossref, Medline, Google Scholar
Kim JH, Lee C, Sohn W. 2016. Urban natural environments, obesity, and health-related quality of life among Hispanic children living in inner-city neighborhoods. Int J Environ Res Public Health 13(1):E121. Crossref, Medline, Google Scholar
Kim W, Lim SK, Chung EJ, Woo JM. 2009. The effect of cognitive behavior therapy-based psychotherapy applied in a forest environment on physiological changes and remission of major depressive disorder. Psychiatry Investig 6(4):245–254, doi:10.4306/pi.2009.6.4.245. Crossref, Medline, Google Scholar
Kimes D, Ullah A, Levine E, Nelson R, Timmins S, Weiss S, et al.2004. Relationships between pediatric asthma and socioeconomic/urban variables in Baltimore, Maryland. Health Place 10(2):141–152, PMID: 15019908, doi:10.1016/S1353-8292(03)00054-6. Crossref, Medline, Google Scholar
Klepeis NE, Nelson WC, Ott WR, Robinson JP, Tsang AM, Switzer P, et al.2001. The National Human Activity Pattern Survey (NHAPS): A resource for assessing exposure to environmental pollutants. J Expo Anal Environ Epidemiol 11(3):231–252, PMID: 11477521, doi:10.1038/sj.jea.7500165. Crossref, Medline, Google Scholar
Kondo MC, South EC, Branas CC. 2015. Nature-based strategies for improving urban health and safety. J Urban Health 92(5):800–814, PMID: 26275455, doi:10.1007/s11524-015-9983-y. Crossref, Medline, Google Scholar
Kondrashova A, Seiskari T, Ilonen J, Knip M, Hyöty H. 2013. The 'hygiene hypothesis' and the sharp gradient in the incidence of autoimmune and allergic diseases between Russian Karelia and Finland. APMIS 121(6):478–493, PMID: 23127244, doi:10.1111/apm.12023. Crossref, Medline, Google Scholar
Koohsari MJ, Sugiyama T, Sahlqvist S, Mavoa S, Hadgraft N, Owen N. 2015. Neighborhood environmental attributes and adults' sedentary behaviors: review and research agenda. Prev Med 77:141–149, PMID: 26051198, doi:10.1016/j.ypmed.2015.05.027. Crossref, Medline, Google Scholar
Kuo F, Faber Taylor A. 2004. A potential natural treatment for attention-deficit/hyperactivity disorder: Evidence from a national study. Am J Public Health 94(9):1580–1586, doi:10.2105/AJPH.94.9.1580. Crossref, Medline, Google Scholar
Kuo FE, Sullivan WC. 2001a. Environment and crime in the inner city: does vegetation reduce crime?Environ Behav 33(3):343–367. Google Scholar
Kuo FE, Sullivan WC. 2001b. Aggression and violence in the inner city: Effects of environment via mental fatigue. Environ Behav 33(4):543–571. Crossref, Google Scholar
Kuo M. 2015. How might contact with nature promote human health? Promising mechanisms and a possible central pathway. Front Psychol 6:1093, doi:10.3389/fpsyg.2015.01093. Crossref, Medline, Google Scholar
Kurzweil R. 2005. The Singularity is Near: When Humans Transcend Biology. New York, NY:Viking. Google Scholar
Kweon B-S, Sullivan WC, Wiley AR. 1998. Green common spaces and the social integration of inner-city older adults. Environ Behav 30(6):832–858, doi:10.1177/001391659803000605. Crossref, Google Scholar
Lachowycz K, Jones AP. 2011. Greenspace and obesity: A systematic review of the evidence. Obes Rev 12(5):e183–e189, PMID: 21348919, doi:10.1111/j.1467-789X.2010.00827.x. Crossref, Medline, Google Scholar
Lachowycz K, Jones AP. 2013. Towards a better understanding of the relationship between greenspace and health: Development of a theoretical framework. Landsc Urban Plan 118:62–69, doi:10.1016/j.landurbplan.2012.10.012. Crossref, Google Scholar
Lachowycz K, Jones AP. 2014. Does walking explain associations between access to greenspace and lower mortality?. Soc Sci Med 107:9–17, PMID: 24602966, doi:10.1016/j.socscimed.2014.02.023. Crossref, Medline, Google Scholar
Larsen FW, Turner WR, Brooks TM. 2012. Conserving critical sites for biodiversity provides disproportionate benefits to people. PLoS One 7(5):e36971, PMID: 22666337, doi:10.1371/journal.pone.0036971. Crossref, Medline, Google Scholar
Larson LR, Jennings V, Cloutier SA. 2016. Public parks and wellbeing in urban areas of the United States. PLoS One 11(4):e0153211, PMID: 27054887, doi:10.1371/journal.pone.0153211. Crossref, Medline, Google Scholar
Lechtzin N, Busse AM, Smith MT, Grossman S, Nesbit S, Diette GB. 2010. A randomized trial of nature scenery and sounds versus urban scenery and sounds to reduce pain in adults undergoing bone marrow aspirate and biopsy. J Altern Complement Med 16(9):965–972, PMID: 20799901, doi:10.1089/acm.2009.0531. Crossref, Medline, Google Scholar
Lee AC, Jordan HC, Horsley J. 2015. Value of urban green spaces in promoting healthy living and wellbeing: prospects for planning. Risk Manag Healthc Policy 8:131–137, PMID: 26347082, doi:10.2147/RMHP.S61654. Crossref, Medline, Google Scholar
Lee ACK, Maheswaran R. 2011. The health benefits of urban green spaces: a review of the evidence. J Public Health (Oxf) 33(2):212–222, PMID: 20833671, doi:10.1093/pubmed/fdq068. Crossref, Medline, Google Scholar
Lee IM, Shiroma EJ, Lobelo F, Puska P, Blair SN, Katzmarzyk PT. 2012. Effect of physical inactivity on major non-communicable diseases worldwide: an analysis of burden of disease and life expectancy. Lancet 380(9838):219–229, PMID: 22818936, doi:10.1016/S0140-6736(12)61031-9. Crossref, Medline, Google Scholar
Lee YK, Mazmanian SK. 2010. Has the microbiota played a critical role in the evolution of the adaptive immune system?. Science 330(6012):1768–1773, PMID: 21205662, doi:10.1126/science.1195568. Crossref, Medline, Google Scholar
Lewis TL, Gould KA. 2017. Green Gentrification: Urban Sustainability and the Struggle for Environmental Justice. Abingdon, UK:Routledge. Google Scholar
Li D, Sullivan WC. 2016. Impact of views to school landscapes on recovery from stress and mental fatigue. Landsc Urban Plan 148:149–158, doi:10.1016/j.landurbplan.2015.12.015. Crossref, Google Scholar
Li Q, Nakadai A, Matsushima H, Miyazaki Y, Krensky AM, Kawada T, et al.2006. Phytoncides (wood essential oils) induce human natural killer cell activity. Immunopharmacol Immunotoxicol 28(2):319–333, PMID: 16873099, doi:10.1080/08923970600809439. Crossref, Medline, Google Scholar
Li Q, Morimoto K, Kobayashi M, Inagaki H, Katsumata M, Hirata Y, et al.2008a. A forest bathing trip increases human natural killer activity and expression of anti-cancer proteins in female subjects. J Biol Regul Homeost Agents 22(1):45–55, PMID: 18394317. Medline, Google Scholar
Li Q, Morimoto K, Kobayashi M, Inagaki H, Katsumata M, Hirata Y, et al.2008b. Visiting a forest, but not a city, increases human natural killer activity and expression of anti-cancer proteins. Int J Immunopathol Pharmacol 21(1):117–127, PMID: 18336737, doi:10.1177/039463200802100113. Crossref, Medline, Google Scholar
Li Q, Kobayashi M, Inagaki H, Hirata Y, Li YJ, Hirata K, et al.2010. A day trip to a forest park increases human natural killer activity and the expression of anti-cancer proteins in male subjects. J Biol Regul Homeost Agents 24(2):157–165. Medline, Google Scholar
Li Q, Kawada T. 2011. Effect of forest environments on human natural killer (NK) activity. Int J Immunopathol Pharmacol 24(1suppl):39S–44S, PMID: 21329564. Medline, Google Scholar
Li X, Meng Q, Li W, Zhang C, Jancso T, Mavromatis S. 2014. An explorative study on the proximity of buildings to green spaces in urban areas using remotely sensed imagery. Ann GIS 20(3):193–203, doi:10.1080/19475683.2014.945482. Crossref, Google Scholar
Li X, Zhang C, Li W, Kuzovkina YA. 2016. Environmental inequities in terms of different types of urban greenery in Hartford, Connecticut. Urb Forestry Urb Greening 18:163–172, doi:10.1016/j.ufug.2016.06.002. Crossref, Google Scholar
Lin YH, Tsai CC, Sullivan WC, Chang PJ, Chang CY. 2014. Does awareness effect the restorative function and perception of street trees?. Front Psychol 5:906, PMID: 25177309, doi:10.3389/fpsyg.2014.00906. Crossref, Medline, Google Scholar
Lindgren E, Elmqvist T. 2017. Ecosystem services and human health. Oxford Research Encyclopedia, Environmental Science. Oxford, UK:Oxford University Press. doi:10.1093/acrefore/9780199389414.013.86. Crossref, Google Scholar
Lioy P, Weisel C. 2014. Exposure Science: Basic Principles and Applications. London, UK:Academic Press. Google Scholar
Liu J, Dietz T, Carpenter SR, Alberti M, Folke C, Moran E, et al.2007. Complexity of coupled human and natural systems. Science 317(5844):1513–1516, PMID: 17872436, doi:10.1126/science.1144004. Crossref, Medline, Google Scholar
Livesley SJ, McPherson GM, Calfapietra C. 2016. The urban forest and ecosystem services: Impacts on urban water, heat, and pollution cycles at the tree, street, and city scale. J Environ Qual 45(1):119–124, PMID: 26828167, doi:10.2134/jeq2015.11.0567. Crossref, Medline, Google Scholar
Lovallo WR. 2015. Stress and Health: Biological and Psychological Interactions. 3rd ed. Thousand Oaks, CA:Sage. Google Scholar
Lovasi GS, O'Neil-Dunne JP, Lu JW, Sheehan D, Perzanowski MS, Macfaden SW, et al.2013. Urban tree canopy and asthma, wheeze, rhinitis, and allergic sensitization to tree pollen in a New York City birth cohort. Environ Health Perspect 121(4):494–500, PMID: 23322788, doi:10.1289/ehp.1205513. Link, Google Scholar
Lovasi GS, Quinn JW, Neckerman KM, Perzanowski MS, Rundle A. 2008. Children living in areas with more street trees have lower prevalence of asthma. J Epidemiol Community Health 62(7):647–649, PMID: 18450765, doi:10.1136/jech.2007.071894. Crossref, Medline, Google Scholar
Lovell R, Wheeler BW, Higgins SL, Irvine KN, Depledge MH. 2014. A systematic review of the health and well-being benefits of biodiverse environments. J Toxicol Environ Health B Crit Rev 17(1):1–20, PMID: 24597907, doi:10.1080/10937404.2013.856361. Crossref, Medline, Google Scholar
Maas J, van Dillen SME, Verheij RA, Groenewegen PP. 2009a. Social contacts as a possible mechanism behind the relation between green space and health. Health Place 15(2):586–595. Crossref, Medline, Google Scholar
Maas J, Verheij R, Groenewegen P, de Vries S, Spreeuwenberg P. 2006. Green space, urbanity, and health: how strong is the relation?. J Epidemiol Community Health 60(7):587–592, PMID: 16790830, doi:10.1136/jech.2005.043125. Crossref, Medline, Google Scholar
Maas J, Verheij RA, de Vries S, Spreeuwenberg P, Schellevis FG, Groenewegen PP. 2009b. Morbidity is related to a green living environment. J Epidemiol Community Health 63(12):967–973, PMID: 19833605, doi:10.1136/jech.2008.079038. Crossref, Medline, Google Scholar
MacFaden SW, O'Neil-Dunne JPM, Royar AR, Lu JWT, Rundle AG. 2012. High-resolution tree canopy mapping for new york city using LIDAR and object-based image analysis. J Appl Remote Sens 6(1):063567, doi:10.1117/1.JRS.6.063567. Crossref, Google Scholar
MacKerron G, Mourato S. 2013. Happiness is greater in natural environments. Global Environmental Change 23(5):992–1000, doi:10.1016/j.gloenvcha.2013.03.010. Crossref, Google Scholar
Mao G, Cao Y, Wang B, Wang S, Chen Z, Wang J, et al.2017. The salutary influence of forest bathing on elderly patients with chronic heart failure. Int J Environ Res Public Health 14(4):368, doi:10.3390/ijerph14040368. Crossref, Medline, Google Scholar
Margaritis E, Kang J. 2017. Relationship between green space-related morphology and noise pollution. Ecol Indic 72:921–933, doi:10.1016/j.ecolind.2016.09.032. Crossref, Google Scholar
Markevych I, Thiering E, Fuertes E, Sugiri D, Berdel D, Koletzko S, et al.2014a. A cross-sectional analysis of the effects of residential greenness on blood pressure in 10-year old children: results from the GINIplus and LISAplus studies. BMC Public Health 14:477, PMID: 24886243, doi:10.1186/1471-2458-14-477. Crossref, Medline, Google Scholar
Markevych I, Tiesler CMT, Fuertes E, Romanos M, Dadvand P, Nieuwenhuijsen MJ, et al.2014b. Access to urban green spaces and behavioural problems in children: results from the GINIplus and LISAplus studies. Environ Int 71:29–35, doi:10.1016/j.envint.2014.06.002. Crossref, Medline, Google Scholar
Martens D, Bauer N. 2013. Natural environments: a resource for public health and well-being? A literature review. Psychology of Well-Being: Theory, Perspectives and Practice. Noehammer E, ed. Hauppauge, NY:Nova Science Publishers, 173–217. Google Scholar
Matchock RL. 2015. Pet ownership and physical health. Curr Opin Psychiatry 28(5):386–392, PMID: 26164613, doi:10.1097/YCO.0000000000000183. Crossref, Medline, Google Scholar
Mazzali C, Duca P. 2015. Use of administrative data in healthcare research. Intern Emerg Med 10(4):517–524, PMID: 25711312, doi:10.1007/s11739-015-1213-9. Crossref, Medline, Google Scholar
McEachan RR, Prady SL, Smith G, Fairley L, Cabieses B, Gidlow C, et al.2016. The association between green space and depressive symptoms in pregnant women: Moderating roles of socioeconomic status and physical activity. J Epidemiol Community Health 70(3):253–259, PMID: 26560759, doi:10.1136/jech-2015-205954. Crossref, Medline, Google Scholar
Melson GF, Kahn PH, Beck A, Friedman B, Roberts T, Garrett E, et al.2009. Children's behavior toward and understanding of robotic and living dogs. Journal of Applied Developmental Psychology 30(2):92–102, doi:10.1016/j.appdev.2008.10.011. Crossref, Google Scholar
Miller JT. 2016. Is urban greening for everyone? Social inclusion and exclusion along the Gowanus Canal. Urban For Urban Green 19:285–294, doi:10.1016/j.ufug.2016.03.004. Crossref, Google Scholar
Mitchell R, Astell-Burt T, Richardson EA. 2011. A comparison of green space indicators for epidemiological research. J Epidemiol Community Health 65(10):853–858, PMID: 21296907, doi:10.1136/jech.2010.119172. Crossref, Medline, Google Scholar
Mitchell R, Popham F. 2007. Greenspace, urbanity and health: relationships in England. J Epidemiol Community Health 61(8):681–683, PMID: 17630365, doi:10.1136/jech.2006.053553. Crossref, Medline, Google Scholar
Mitchell R, Popham F. 2008. Effect of exposure to natural environment on health inequalities: An observational population study. Lancet 372(9650):1655–1660, doi:10.1016/S0140-6736(08)61689-X. Crossref, Medline, Google Scholar
Mitchell RJ, Richardson EA, Shortt NK, Pearce JR. 2015. Neighborhood environments and socioeconomic inequalities in mental well-being. Am J Prev Med 49(1):80–84, PMID: 25911270, doi:10.1016/j.amepre.2015.01.017. Crossref, Medline, Google Scholar
Morita E, Imai M, Okawa M, Miyaura T, Miyazaki S. 2011. A before and after comparison of the effects of forest walking on the sleep of a community-based sample of people with sleep complaints. Biopsychosoc Med 5:13, PMID: 21999605, doi:10.1186/1751-0759-5-13. Crossref, Medline, Google Scholar
Murgui E, Hedblom M. 2017. Ecology and Conservation of Birds in Urban Environments. Cham, Switzerland:Springer. Crossref, Google Scholar
Naidoo R, Balmford A, Ferraro PJ, Polasky S, Ricketts TH, Rouget M. 2006. Integrating economic costs into conservation planning. Trends Ecol Evol 21(12):681–687, PMID: 17050033, doi:10.1016/j.tree.2006.10.003. Crossref, Medline, Google Scholar
Nicolaou N, Siddique N, Custovic A. 2005. Allergic disease in urban and rural populations: increasing prevalence with increasing urbanization. Allergy 60(11):1357–1360, doi:10.1111/j.1398-9995.2005.00961.x. Crossref, Medline, Google Scholar
Nielsen TS, Hansen KB. 2007. Do green areas affect health? Results from a Danish survey on the use of green areas and health indicators. Health Place 13(4):839–850, doi:10.1016/j.healthplace.2007.02.001. Crossref, Medline, Google Scholar
Nielsen. 2016. The Nielsen Total Audience Report: Q1, 2016. http://www.nielsen.com/us/en/insights/reports/2016/the-total-audience-report-q1-2016.html [accessed 5 July 2017]. Google Scholar
Nieuwenhuijsen MJ, ed. 2003. Exposure Assessment in Occupational and Environmental Epidemiology. New York, NY:Oxford University Press. Crossref, Google Scholar
Ninan KN, Costanza R. 2014. Valuing Ecosystem Services: Methodological Issues and Case Studies. Cheltenham, UK:Edward Elgar Publishing Limited. Crossref, Google Scholar
Nowak DJ, Appleton N, Ellis A, Greenfield E. 2017. Residential building energy conservation and avoided power plant emissions by urban and community trees in the United States. Urb Forestry Urb Greening 21:158–165, doi:10.1016/j.ufug.2016.12.004. Crossref, Google Scholar
Nowak DJ, Hirabayashi S, Bodine A, Greenfield E. 2014. Tree and forest effects on air quality and human health in the United States. Environ Pollut 193:119–129, PMID: 25016465, doi:10.1016/j.envpol.2014.05.028. Crossref, Medline, Google Scholar
Nowak DJ, Hirabayashi S, Bodine A, Hoehn R. 2013. Modeled PM_2.5 removal by trees in ten U.S. cities and associated health effects. Environ Pollut 178:395–402, PMID: 23624337, doi:10.1016/j.envpol.2013.03.050. Crossref, Medline, Google Scholar
NRPA (National Recreation and Parks Association). 2015. The economic impact of local parks: An examination of the economic impacts of operations and capital spending on the United States economy. Ashburn, VA:National Recreation and Parks Association. http://www.nrpa.org/publications-research/research-papers/the-economic-impact-of-local-parks/ [accessed 5 July 2017]. Google Scholar
Nusslock R, Miller GE. 2016. Early-life adversity and physical and emotional health across the lifespan: A neuroimmune network hypothesis. Biol Psychiatry 80(1):23–32, PMID: 26166230, doi:10.1016/j.biopsych.2015.05.017. Crossref, Medline, Google Scholar
Nutsford D, Pearson AL, Kingham S. 2013. An ecological study investigating the association between access to urban green space and mental health. Public Health 127(11):1005–1011, PMID: 24262442, doi:10.1016/j.puhe.2013.08.016. Crossref, Medline, Google Scholar
O'Donoghue G, Perchoux C, Mensah K, Lakerveld J, van der Ploeg H, Bernaards C, et al.2016. A systematic review of correlates of sedentary behaviour in adults aged 18-65 years: A socio-ecological approach. BMC Public Health 16(1):163. Crossref, Medline, Google Scholar
Park S-H, Mattson RH. 2008. Effects of flowering and foliage plants in hospital rooms on patients recovering from abdominal surgery. HortTechnology 18(4):563–568. Crossref, Google Scholar
Park SH, Mattson RH. 2009. Ornamental indoor plants in hospital rooms enhanced health outcomes of patients recovering from surgery. J Altern Complement Med 15(9):975–980, PMID: 19715461, doi:10.1089/acm.2009.0075. Crossref, Medline, Google Scholar
Parsons R, Tassinary LG, Ulrich RS, Hebl MR, Grossman-Alexander M. 1998. The view from the road: Implications for stress recovery and immunization. J Environ Psychol 18(2):113–140, doi:10.1006/jevp.1998.0086. Crossref, Google Scholar
Payne LL, Mowen AJ, Orsega-Smith E. 2002. An examination of park preferences and behaviors among urban residents: The role of residential location, race, and age. Leis Sci 24(2):181–198, doi:10.1080/01490400252900149. Crossref, Google Scholar
Pearl J, Glymour M, Jewell NP. 2016. Causal Inference in Statistics: A Primer. Chichester, UK: John Wiley & Sons Ltd. Google Scholar
Pearl J. 2009. Causality: Models, Reasoning, and Inference. 2nd ed. Cambridge, UK:Cambridge University Press. Crossref, Google Scholar
Pedlowski MA, Da Silva VAC, Adell JJC, Heynen NC. 2002. Urban forest and environmental inequality in Campos dos Goytacazes, Rio de Janeiro, Brazil. Urban Ecosyst 6(1–2):9–20, doi:10.1023/A:1025910528583. Crossref, Google Scholar
Pergams OR, Zaradic PA. 2008. Evidence for a fundamental and pervasive shift away from nature-based recreation. Proc Natl Acad Sci U S A 105(7):2295–2300, doi:10.1073/pnas.0709893105. Crossref, Medline, Google Scholar
Perrin JL, Benassi VA. 2009. The connectedness to nature scale: A measure of emotional connection to nature?. J Environ Psychol 29(4):434–440, doi:10.1016/j.jenvp.2009.03.003. Crossref, Google Scholar
Piff PK, Dietze P, Feinberg M, Stancato DM, Keltner D. 2015. Awe, the small self, and prosocial behavior. J Pers Soc Psychol 108(6):883–899, PMID: 25984788, doi:10.1037/pspi0000018. Crossref, Medline, Google Scholar
Pliakas T, Hawkesworth S, Silverwood RJ, Nanchahal K, Grundy C, Armstrong B, et al.2017. Optimising measurement of health-related characteristics of the built environment: Comparing data collected by foot-based street audits, virtual street audits and routine secondary data sources. Health Place 43:75–84, PMID: 27902960, doi:10.1016/j.healthplace.2016.10.001. Crossref, Medline, Google Scholar
Posner SM, McKenzie E, Ricketts TH. 2016. Policy impacts of ecosystem services knowledge. Proc Natl Acad Sci USA 113(7):1760–1765, PMID: 26831101, doi:10.1073/pnas.1502452113. Crossref, Medline, Google Scholar
Poulsen DV, Stigsdotter UK, Refshage AD. 2015. Whatever happened to the soldiers? Nature-assisted therapies for veterans diagnosed with post-traumatic stress disorder: A literature review. Urb Forestry Urb Greening 14(2):438–445, doi:10.1016/j.ufug.2015.03.009. Crossref, Google Scholar
Qviström M. 2016. The nature of running: on embedded landscape ideals in leisure planning. Urban Forestry & Urban Greening 17:202–210, doi:10.1016/j.ufug.2016.04.012. Crossref, Google Scholar
Radesky JS, Christakis DA. 2016. Increased screen time: implications for early childhood development and behavior. Pediatr Clin North Am 63(5):827–839, PMID: 27565361, doi:10.1016/j.pcl.2016.06.006. Crossref, Medline, Google Scholar
Ray H, Jakubec SL. 2014. Nature-based experiences and health of cancer survivors. Complement Ther Clin Pract 20(4):188–192, PMID: 25160991, doi:10.1016/j.ctcp.2014.07.005. Crossref, Medline, Google Scholar
Rhew IC, Vander Stoep A, Kearney A, Smith NL, Dunbar MD. 2011. Validation of the Normalized Difference Vegetation Index as a measure of neighborhood greenness. Ann Epidemiol 21(12):946–952, PMID: 21982129, doi:10.1016/j.annepidem.2011.09.001. Crossref, Medline, Google Scholar
Rideout VJ, Foehr UG, Roberts DF. 2010. Generation M2: Media in the lives of 8- to 18-year-olds. Henry J. Kaiser Family Foundation. http://www.kff.org/other/report/generation-m2-media-in-the-lives-of-8-to-18-year-olds/ [accessed 5 July 2017]. Google Scholar
Rideout VJ. 2013. Zero to eight: children's media use in America 2013. Common Sense Media. https://www.commonsensemedia.org/research/zero-to-eight-childrens-media-use-in-america-2013 [accessed 5 July 2017]. Google Scholar
Rigolon A. 2016. A complex landscape of inequity in access to urban parks: A literature review. Landsc Urban Plan 153:160–169, doi:10.1016/j.landurbplan.2016.05.017. Crossref, Google Scholar
Roe J, Aspinall P. 2011. The restorative outcomes of forest school and conventional school in young people with good and poor behaviour. Urb Forestry Urb Greening 10(3):205–212, doi:10.1016/j.ufug.2011.03.003. Crossref, Google Scholar
Roe J, Aspinall PA, Mavros P, Coyne R. 2013. Engaging the brain: The impact of natural versus urban scenes using novel EEG methods in an experimental setting. Environ Sci 1(2):93–104, doi:10.12988/es.2013.3109. Crossref, Google Scholar
Roe JJ, Thompson CW, Aspinall PA, Brewer MJ, Duff EI, Miller D, et al.2013. Green space and stress: Evidence from cortisol measures in deprived urban communities. Int J Environ Res Public Health 10(9):4086–4103, PMID: 24002726, doi:10.3390/ijerph10094086. Crossref, Medline, Google Scholar
Rook GA. 2013. Regulation of the immune system by biodiversity from the natural environment: An ecosystem service essential to health. Proc Natl Acad Sci USA 110(46):18360–18367, PMID: 24154724, doi:10.1073/pnas.1313731110. Crossref, Medline, Google Scholar
Roy S, Byrne J, Pickering C. 2012. A systematic quantitative review of urban tree benefits, costs, and assessment methods across cities in different climatic zones. Urb Forestry Urb Greening 11(4):351–363, doi:10.1016/j.ufug.2012.06.006. Crossref, Google Scholar
Ruckelshaus M, McKenzie E, Tallis H, Guerry A, Daily G, Kareiva P, et al.2015. Notes from the field: lessons learned from using ecosystem service approaches to inform real-world decisions. Ecol Econ 115:11–21, doi:10.1016/j.ecolecon.2013.07.009. Crossref, Google Scholar
Rudd M, Vohs KD, Aaker J. 2012. Awe expands people's perception of time, alters decision making, and enhances well-being. Psychol Sci 23(10):1130–1136, PMID: 22886132, doi:10.1177/0956797612438731. Crossref, Medline, Google Scholar
Rundle AG, Bader MDM, Richards CA, Neckerman KM, Teitler JO. 2011. Using Google Street View to audit neighborhood environments. Amn J Prev Med 40(1):94–100, doi:10.1016/j.amepre.2010.09.034. Crossref, Medline, Google Scholar
Ruokolainen L, von Hertzen L, Fyhrquist N, Laatikainen T, Lehtomaki J, Auvinen P, et al.2015. Green areas around homes reduce atopic sensitization in children. Allergy 70(2):195–202, PMID: 25388016, doi:10.1111/all.12545. Crossref, Medline, Google Scholar
Russell R, Guerry AD, Balvanera P, Gould RK, Basurto X, Chan KMA, et al.2013. Humans and nature: how knowing and experiencing nature affect well-being. Annu Rev Environ Resour 38:473–502, doi:10.1146/annurev-environ-012312-110838. Crossref, Google Scholar
Rutt RL, Gulsrud NM. 2016. Green justice in the city: a new agenda for urban green space research in europe. Urb Forestry Urb Greening 19:123–127, doi:10.1016/j.ufug.2016.07.004. Crossref, Google Scholar
Rutter M. 2007. Proceeding from observed correlation to causal inference: the use of natural experiments. Perspect Psychol Sci 2(4):377–395, doi:10.1111/j.1745-6916.2007.00050.x. Crossref, Medline, Google Scholar
Salmond JA, Tadaki M, Vardoulakis S, Arbuthnott K, Coutts A, Demuzere M, et al.2016. Health and climate related ecosystem services provided by street trees in the urban environment. Environ Health 15(suppl 1):S36, doi:10.1186/s12940-016-0103-6. Crossref, Medline, Google Scholar
Sanders T, Feng X, Fahey PP, Lonsdale C, Astell-Burt T. 2015. Greener neighbourhoods, slimmer children? Evidence from 4423 participants aged 6 to 13 years in the Longitudinal Study of Australian Children. Int J Obes (Lond) 39(8):1224–1229, PMID: 25916908, doi:10.1038/ijo.2015.69. Crossref, Medline, Google Scholar
Sandifer PA, Sutton-Grier AE, Ward BP. 2015. Exploring connections among nature, biodiversity, ecosystem services, and human health and well-being: Opportunities to enhance health and biodiversity conservation. Ecosyst Serv 12:1–15, doi:10.1016/j.ecoser.2014.12.007. Crossref, Google Scholar
Schootman M, Nelson EJ, Werner K, Shacham E, Elliott M, Ratnapradipa K, et al.2016. Emerging technologies to measure neighborhood conditions in public health: implications for interventions and next steps. Int J Health Geogr 15(1):20, PMID: 27339260, doi:10.1186/s12942-016-0050-z. Crossref, Medline, Google Scholar
Schutte NS, Bhullar N, Stilinović EJ, Richardson K. 2017. The impact of virtual environments on restorativeness and affect. Ecopsychology 9(1):1–7, doi:10.1089/eco.2016.0042. Crossref, Google Scholar
Schwarz K, Fragkias M, Boone CG, Zhou W, McHale M, Grove JM, et al.2015. Trees grow on money: urban tree canopy cover and environmental justice. PLoS One 10(4):e0122051, PMID: 25830303, doi:10.1371/journal.pone.0122051. Crossref, Medline, Google Scholar
Seppelt R, Dormann CF, Eppink FV, Lautenbach S, Schmidt S. 2011. A quantitative review of ecosystem service studies: approaches, shortcomings and the road ahead. J Appl Ecol 48(3):630–636, doi:10.1111/j.1365-2664.2010.01952.x. Crossref, Google Scholar
Seresinhe CI, Preis T, Moat HS. 2015. Quantifying the impact of scenic environments on health. Sci Rep 5:16899, PMID: 26603464, doi:10.1038/srep16899. Crossref, Medline, Google Scholar
Sessions C, Wood SA, Rabotyagov S, Fisher DM. 2016. Measuring recreational visitation at U.S. National Parks with crowd-sourced photographs. J Environ Manage 183(Part 3):703–711, doi:10.1016/j.jenvman.2016.09.018. Crossref, Medline, Google Scholar
Seymour V. 2016. The human–nature relationship and its impact on health: A critical review. Front Public Health 4:260, doi:10.3389/fpubh.2016.00260. Crossref, Medline, Google Scholar
Shanahan DF, Fuller RA, Bush R, Lin BB, Gaston KJ. 2015a. The health benefits of urban nature: how much do we need?BioScience 65(5):476–485, doi:10.1093/biosci/biv032. Crossref, Google Scholar
Shanahan DF, Lin BB, Bush R, Gaston KJ, Dean JH, Barber E, et al.2015b. Toward improved public health outcomes from urban nature. Am J Public Health 105(3):470–477, PMID: 25602866, doi:10.2105/AJPH.2014.302324. Crossref, Medline, Google Scholar
Shanahan DF, Bush R, Gaston KJ, Lin BB, Dean J, Barber E, et al.2016. Health benefits from nature experiences depend on dose. Sci Rep 6:28551, PMID: 27334040, doi:10.1038/srep28551. Crossref, Medline, Google Scholar
Shanahan DF, Franco L, Lin BB, Gaston KJ, Fuller RA. 2016. The benefits of natural environments for physical activity. Sports Med 46(7):989–995. Crossref, Medline, Google Scholar
Shiota MN, Keltner D, Mossman A. 2007. The nature of awe: elicitors, appraisals, and effects on self-concept. Cogn Emot 21(5):944–963, doi:10.1080/02699930600923668. Crossref, Google Scholar
Shoup L, Ewing R. 2010. The economic benefits of open space, recreation facilities and walkable community design. Princeton NJ and San Diego CA:Robert Wood Johnson Foundation, Active Living Research Program. http://activelivingresearch.org/economic-benefits-open-space-recreation-facilities-and-walkable-community-design [accessed 5 July 2017]. Google Scholar
Smiley KT, Sharma T, Steinberg A, Hodges-Copple S, Jacobson E, Matveeva L. 2016. More inclusive parks planning: Park quality and preferences for park access and amenities. Environ Justice 9(1):1–7, doi:10.1089/env.2015.0030. Crossref, Google Scholar
Smith LM, Case JL, Smith HM, Harwell LC, Summers JK. 2013. Relating ecoystem services to domains of human well-being: Foundation for a U.S. index. Ecol Ind 28:79–90, doi:10.1016/j.ecolind.2012.02.032. Crossref, Google Scholar
Snow J. 1855. On the Mode of Communication of Cholera. London, UK:John Churchill. Google Scholar
Söderström M, Boldemann C, Sahlin U, Mårtensson F, Raustorp A, Blennow M. 2013. The quality of the outdoor environment influences childrens health – a cross-sectional study of preschools. Acta Paediatr 102(1):83–91, PMID: 23035750, doi:10.1111/apa.12047. Crossref, Medline, Google Scholar
Song C, Joung D, Ikei H, Igarashi M, Aga M, Park BJ, et al.2013. Physiological and psychological effects of walking on young males in urban parks in winter. J Physiol Anthropol 32:18, doi:10.1186/1880-6805-32-18. Crossref, Medline, Google Scholar
Song C, Ikei H, Igarashi M, Takagaki M, Miyazaki Y. 2015. Physiological and psychological effects of a walk in urban parks in fall. Int J Environ Res Public Health 12(11):14216–14228, PMID: 26569271, doi:10.3390/ijerph121114216. Crossref, Medline, Google Scholar
Stagl S, Common MS. 2005. Ecological Economics: An Introduction. Cambridge, UK:Cambridge University Press. Google Scholar
Stark JH, Neckerman K, Lovasi GS, Quinn J, Weiss CC, Bader MDM, et al.2014. The impact of neighborhood park access and quality on body mass index among adults in New York City. Prev Med 64:63–68, PMID: 24704504, doi:10.1016/j.ypmed.2014.03.026. Crossref, Medline, Google Scholar
Stiemsma LT, Reynolds LA, Turvey SE, Finlay BB. 2015. The hygiene hypothesis: Current perspectives and future therapies. ImmunoTargets Ther 4:143–157, PMID: 27471720, doi:10.2147/ITT.S61528. Crossref, Medline, Google Scholar
Stier AC, Samhouri JF, Gray S, Martone RG, Mach ME, Halpern BS, et al.2017. Integrating expert perceptions into food web conservation and management. Conservation Letters 10(1):67–76, doi:10.1111/conl.12245. Crossref, Google Scholar
Stigsdotter UK, Ekholm O, Schipperijn J, Toftager M, Kamper-Jørgensen F, Randrup TB. 2010. 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 38(4):411–417, PMID: 20413584, doi:10.1177/1403494810367468. Crossref, Medline, Google Scholar
Sturm R, Cohen D. 2014. Proximity to urban parks and mental health. J Ment Health Policy Econ 17(1):19–24, PMID: 24864118. Medline, Google Scholar
Sugiyama T, Cerin E, Owen N, Oyeyemi AL, Conway TL, Van Dyck D, et al.2014. Perceived neighbourhood environmental attributes associated with adults recreational walking: IPEN adult study in 12 countries. Health Place 28:22–30, PMID: 24721737, doi:10.1016/j.healthplace.2014.03.003. Crossref, Medline, Google Scholar
Sullivan WC, Kaplan R. 2016. Nature! Small steps that can make a big difference. HERD 9(2):6–10, PMID: 26698884, doi:10.1177/1937586715623664. Crossref, Medline, Google Scholar
Sullivan WC, Kuo FE, DePooter SF. 2004. The fruit of urban nature: vital neighborhood spaces. Environ Behav 36(5):678–700, doi:10.1177/0193841X04264945. Crossref, Google Scholar
Szolosi AM, Watson JM, Ruddell EJ. 2014. The benefits of mystery in nature on attention: assessing the impacts of presentation duration. Front Psychol 5:1360, doi:10.3389/fpsyg.2014.01360. Crossref, Medline, Google Scholar
Takano T, Nakamura K, Watanabe M. 2002. Urban residential environments and senior citizens’ longevity in megacity areas: the importance of walkable green spaces. J Epidemiol Community Health 56(12):913–918, PMID: 12461111. Crossref, Medline, Google Scholar
Taylor AF, Kuo FE, Sullivan WC. 2002. Views of nature and self-discipline: evidence from inner city children. J Environ Psychol 22(1–2):49–63, doi:10.1006/jevp.2001.0241. Crossref, Google Scholar
Taylor BT, Fernando P, Bauman AE, Williamson A, Craig JC, Redman S. 2011. Measuring the quality of public open space using Google Earth. Am J Prev Med 40(2):105–112, PMID: 21238857, doi:10.1016/j.amepre.2010.10.024. Crossref, Medline, Google Scholar
Taylor L, Hochuli DF. 2017. Defining greenspace: multiple uses across multiple disciplines. Landsc Urban Plan 158:25–38, doi:10.1016/j.landurbplan.2016.09.024. Crossref, Google Scholar
Taylor MS, Wheeler BW, White MP, Economou T, Osborne NJ. 2015. Research note: urban street tree density and antidepressant prescription rates—a cross-sectional study in London, UK. Landscape and Urban Planning 136:174–179, doi:10.1016/j.landurbplan.2014.12.005. Crossref, Google Scholar
Thiering E, Markevych I, Bruske I, Fuertes E, Kratzsch J, Sugiri D, et al.2016. Associations of residential long-term air pollution exposures and satellite-derived greenness with insulin resistance in German adolescents. Environ Health Perspect 124(8):1291–1298, PMID: 26863688, doi:10.1289/ehp.1509967. Link, Google Scholar
Threlfall CG, Walker K, Williams NSG, Hahs AK, Mata L, Stork N, et al.2015. The conservation value of urban green space habitats for australian native bee communities. Biological Conservation 187:240–248, doi:10.1016/j.biocon.2015.05.003. Crossref, Google Scholar
Tilley S, Neale C, Patuano A, Cinderby S. 2017. Older people's experiences of mobility and mood in an urban environment: a mixed methods approach using electroencephalography (EEG) and interviews. Int J Environ Res Public Health 14(2):151, doi:10.3390/ijerph14020151. Crossref, Medline, Google Scholar
Triguero-Mas M, Dadvand P, Cirach M, Martínez D, Medina A, Mompart A, et al.2015. Natural outdoor environments and mental and physical health: relationships and mechanisms. Environ Int 77:35–41, PMID: 25638643, doi:10.1016/j.envint.2015.01.012. Crossref, Medline, Google Scholar
Troy A, Morgan Grove J, O’Neil-Dunne J. 2012. The relationship between tree canopy and crime rates across an urban–rural gradient in the greater Baltimore region. Landsc Urban Plan 106(3):262–270, doi:10.1016/j.landurbplan.2012.03.010. Crossref, Google Scholar
Tzoulas K, Korpela K, Venn S, Yli-Pelkonen V, Kaźmierczak A, Niemela J, et al.2007. Promoting ecosystem and human health in urban areas using green infrastructure: a literature review. Landscape and Urban Planning 81(3):167–178, doi:10.1016/j.landurbplan.2007.02.001. Crossref, Google Scholar
Ulrich RS, Simons RF, Losito BD, Fiorito E, Miles MA, Zelson M. 1991. Stress recovery during exposure to natural and urban environments. J Environ Psychol 11(3):201–230, doi:10.1016/S0272-4944(05)80184-7. Crossref, Google Scholar
Ulrich RS. 1984. View through a window may influence recovery from surgery. Science 224(4647):420–421, PMID: 6143402. Crossref, Medline, Google Scholar
United Nations, Population Division. 2015. World Urbanization Prospects. The 2014 revision. New York, NY:United Nations. https://esa.un.org/unpd/wup/ [accessed 5 July 2017]. Google Scholar
van den Berg A, Custers M. 2011. Gardening promotes neuroendocrine and affective restoration from stress. J Health Psychol 16(1):3–11, PMID: 20522508, doi:10.1177/1359105310365577. Crossref, Medline, Google Scholar
van den Berg AE, Maas J, Verheij RA, Groenewegen PP. 2010. Green space as a buffer between stressful life events and health. Soc Sci Med 70(8):1203–1210, PMID: 20163905, doi:10.1016/j.socscimed.2010.01.002. Crossref, Medline, Google Scholar
van den Berg AE, van den Berg CG. 2011. A comparison of children with ADHD in a natural and built setting. Child Care Health Dev 37(3):430–439, PMID: 21143265, doi:10.1111/j.1365-2214.2010.01172.x. Crossref, Medline, Google Scholar
Van Herzele A, de Vries S. 2012. Linking green space to health: A comparative study of two urban neighbourhoods in Ghent, Belgium. Popul Environ 34(2):171–193, doi:10.1007/s11111-011-0153-1. Crossref, Google Scholar
Vanderloo LM. 2014. Screen-viewing among preschoolers in childcare: A systematic review. BMC Pediatr 14:205, PMID: 25129567, doi:10.1186/1471-2431-14-205. Crossref, Medline, Google Scholar
Vaughan KB, Kaczynski AT, Wilhelm Stanis SA, Besenyi GM, Bergstrom R, Heinrich KM. 2013. Exploring the distribution of park availability, features, and quality across Kansas City, Missouri by income and race/ethnicity: An environmental justice investigation. Ann Behav Med 45(suppl 1):28–38, doi:10.1007/s12160-012-9425-y. Crossref, Google Scholar
Verra ML, Angst F, Beck T, Lehmann S, Brioschi R, Schneiter R, et al.2012. Horticultural therapy for patients with chronic musculoskeletal pain: results of a pilot study. Altern Ther Health Med 18(2):44–50, PMID: 22516884. Medline, Google Scholar
Villeneuve PJ, Jerrett M, G. Su J, Burnett RT, Chen H, Wheeler AJ, et al.2012. A cohort study relating urban green space with mortality in Ontario, Canada. Environ Res 115:51–58, doi:10.1016/j.envres.2012.03.003. Crossref, Medline, Google Scholar
Vos PE, Maiheu B, Vankerkom J, Janssen S. 2013. Improving local air quality in cities: to tree or not to tree?. Environ Pollut 183:113–122, doi:10.1016/j.envpol.2012.10.021. Crossref, Medline, Google Scholar
Ward Thompson C, Aspinall P, Roe J, Robertson L, Miller D. 2016. Mitigating stress and supporting health in deprived urban communities: The importance of green space and the social environment. Int J Environ Res Public Health 13(4):440, PMID: 27110803, doi:10.3390/ijerph13040440. Crossref, Medline, Google Scholar
Wells NM, Lekies KS. 2006. Nature and the life course: Pathways from childhood nature experiences to adult environmentalism. Child Youth Environ 16(1):1–24. Crossref, Google Scholar
Wen M, Zhang X, Harris CD, Holt JB, Croft JB. 2013. Spatial disparities in the distribution of parks and green spaces in the USA. Ann Behav Med 45(suppl 1):18–27, doi:10.1007/s12160-012-9426-x. Crossref, Google Scholar
Wheeler BW, Lovell R, Higgins SL, White MP, Alcock I, Osborne NJ, et al.2015. Beyond greenspace: an ecological study of population general health and indicators of natural environment type and quality. Int J Health Geogr 14:17, doi:10.1186/s12942-015-0009-5. Crossref, Medline, Google Scholar
White M, Smith A, Humphryes K, Pahl S, Snelling D, Depledge M. 2010. Blue space: the importance of water for preference, affect, and restorativeness ratings of natural and built scenes. J Environ Psychol 30(4):482–493, doi:10.1016/j.jenvp.2010.04.004. Crossref, Google Scholar
White MP, Alcock I, Wheeler BW, Depledge MH. 2013. Would you be happier living in a greener urban area? A fixed-effects analysis of panel data. Psychol Sci 24(6):920–928, doi:10.1177/0956797612464659. Crossref, Medline, Google Scholar
WHO (World Health Organization). 2010. Global Recommendations on Physical Activity for Health. Geneva:World Health Organization. Google Scholar
Willis KJ, Petrokofsky G. 2017. The natural capital of city trees. Science 356(6336):374–376, PMID: 28450596, doi:10.1126/science.aam9724. Crossref, Medline, Google Scholar
Wilson EO. 1984. Biophilia. Cambridge, MA:Harvard University Press. Crossref, Google Scholar
Witten K, Hiscock R, Pearce J, Blakely T. 2008. Neighbourhood access to open spaces and the physical activity of residents: A national study. Prev Med 47(3):299–303, PMID: 18533242, doi:10.1016/j.ypmed.2008.04.010. Crossref, Medline, Google Scholar
Wolch JR, Byrne J, Newell JP. 2014. Urban green space, public health, and environmental justice: The challenge of making cities ‘just green enough. Landsc Urban Plan 125:234–244, doi:10.1016/j.landurbplan.2014.01.017. Crossref, Google Scholar
Wolf KL, Measells MK, Grado SC, Robbins AST. 2015. Economic values of metro nature health benefits: A life course approach. Urb Forestry Urb Greening 14(3):694–701, doi:10.1016/j.ufug.2015.06.009. Crossref, Google Scholar
Wolf KL, Robbins AS. 2015. Metro nature, environmental health, and economic value. Environ Health Perspect 123(5):390–398, PMID: 25626137, doi:10.1289/ehp.1408216. Link, Google Scholar
Woo J, Tang N, Suen E, Leung J, Wong M. 2009. Green space, psychological restoration, and telomere length. Lancet 373(9660):299–300, PMID: 19167568, doi:10.1016/S0140-6736(09)60094-5. Crossref, Medline, Google Scholar
Wood SA, Guerry AD, Silver JM, Lacayo M. 2013. Using social media to quantify nature-based tourism and recreation. Sci Rep 3:2976, PMID: 24131963, doi:10.1038/srep02976. Crossref, Medline, Google Scholar
Younan D, Tuvblad C, Li L, Wu J, Lurmann F, Franklin M, et al.2016. Environmental determinants of aggression in adolescents: Role of urban neighborhood greenspace. J Am Acad Child Adolesc Psychiatry 55(7):591–601, PMID: 27343886, doi:10.1016/j.jaac.2016.05.002. Crossref, Medline, Google Scholar
Zartarian V, Bahadori T, McKone T. 2005. Adoption of an official ISEA glossary. J Expo Anal Environ Epidemiol 15(1):1–5, PMID: 15562291, doi:10.1038/sj.jea.7500411. Crossref, Medline, Google Scholar
Zelenski JM, Dopko RL, Capaldi CA. 2015. Cooperation is in our nature: Nature exposure may promote cooperative and environmentally sustainable behavior. J Environ Psychol 42:24–31, doi:10.1016/j.jenvp.2015.01.005. Crossref, Google Scholar