RESEARCH REPORT The Health Benefits of Parks and their Economic Impacts A Review of the Literature Mychal Cohen Kimberly Burrowes Peace Gwam February 2022 RESEARCH TO ACTION LAB
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Contents Acknowledgments v Executive Summary vi Introduction 1 Methodology 3 Park Characteristics 5 Quality and Accessibility 5 Urban versus Rural 7 Size of Park or Green space 8 Safety in Park spaces 8 Physical Health 10 Connections between Parks and Physical Activity 10 Physical Activity and Health Outcomes 11 Health Impacts of General Park Usage and Green Space 12 Mental Health 13 Mental Well-Being 13 Use of Mental Health Services 14 Functioning and Productivity 14 Social Health 15 Social Cohesion 15 Social Capital 16 Environmental Health 17 Air Quality 17 Climate Adaptations 17 Disaster Planning and Social Resilience 18 Economic Impacts of Park Health Benefits 20 Methods for Quantifying the Economic Impacts of Park Health Benefits 22 Hedonic Modeling 22 Benefits Transfer 23 Benefits Tools 23 Considerations for a Health Equity Framework 24
iv CONTENTS The Literature Is Strongest for Quantifying Physical, Mental, and Environmental Health Outcomes in Parks 24 Confirming the Actual Relationship between Parks and Outcomes Is Challenging 24 Additional Research Is Needed to Understand the Connection between Parks and Larger Health Systems 25 Notes 26 References 27 About the Authors 35 Statement of Independence 36
ACKNOWLEDGMENTS v Acknowledgments This report was funded by the National Recreation and Park Association. We are grateful to them and to all our funders, who make it possible for Urban to advance its mission. The views expressed are those of the authors and should not be attributed to the Urban Institute, its trustees, or its funders. Funders do not determine research findings or the insights and recommendations of Urban experts. Further information on the Urban Institute’s funding principles is available at urban.org/fundingprinciples. This work was made possible by the generous support of The JPB Foundation. We would also like to thank the experts on the project’s advisory committee, who offered their comments and perspectives to strengthen this resource. The committee included Enessa Janes, Climate Adaptation and Resilience Principle Planner, City of Denver, CO, Ryan Longoria, City of Mount Pleasant Parks and Recreation; Homer Garcia III, San Antonio Parks & Recreation; Nick Pitas, SUNY Brockport; Jessica Sargent, Primrose Research, LLC; Victor Cardenas, CAPRA commission, ICMA Board member; Marissa Ramirez, Natural Resources Defense Council; Jamie Chriqui, UIC School of Public Health; Patrick Guerriero, Civitas Public Affairs Group; and Daphne Lundi, Black Space Urban Collaborative. We would also like to thank our thoughtful Urban Institute reviewers, Matthew Eldridge and Mark Treskon. Their expertise in place-based approaches and overall feedback from scoping to writing truly grounded this report as an important resource for the park and green space field.
vi EXECUTIVE SUMMARY Executive Summary Parks and green spaces1 have intrinsic value, but they also provide a range of direct and indirect benefits that support healthy, productive lives and resilient, cohesive communities. Many of these health and resilience benefits are quantifiable and well documented and can be expressed in terms of their economic impacts on individuals and communities. Measuring, understanding, and communicating the economic health benefits of park equity will help park leaders, community advocates, and other stakeholders make informed decisions about park and green space investments. Evidence suggests that parks and green spaces have significant benefits for their users, with additional benefits accruing with investments in park and green space access and quality. This is fueled, in part, by a growing recognition of the broader utility and value of parks for individuals and communities. Park leaders and advocates are identifying ways to unlock the full potential of parks to spur economic benefits for neighborhoods and residents, foster belonging and collective identity, and provide health benefits for users. Health benefits can be measured as both direct contributions as well as averted health expenditures. But the benefits of parks have not traditionally accrued to all. To ensure equitable access to high-quality parks, policymakers and local leaders must acknowledge the legacies of slavery, racial violence, redlining, and other forms of oppression that have prevented people of color from experiencing parks and green space. Evidence on health benefits highlight the importance of contextualizing who has access to parks and green spaces and whether that access is equitable. This document advances this process by situating parks within broader conversations on equity and access and providing a comprehensive summary of the research on the health equity benefits of parks. Four dimensions of health are discussed in this report—physical, mental, social, and environmental—to demonstrate the range of health benefits from parks and green space, and where possible, the economic impacts of these contributions. This report presents the evidence described in recent, relevant literature to support local leaders, park professionals, advocates, and others to advance the field of park and green space health equity with more strategic investments. There is moderate to strong evidence, qualitative and quantitative, showing that parks have a substantial contribution to health across all four dimensions. The strongest evidence establishes parks’ benefits on physical health. Several studies highlight the link between time spent in parks and physical activity and the correlation between that activity and positive health outcomes, such as a reduced risk of cardiovascular disease, diabetes, cancer, and heart disease. Research suggests that park usage also
EXECUTIVE SUMMARY vii positively affects mental health by reducing stress levels and improving mood, with onward benefits from those outcomes to decreased use of mental health services and increased job productivity. With regards to social health, research suggests an association between parks and social cohesion and belonging whereby users experience greater community attachment with exposure to, and activities or programs in, local green spaces. Studies also suggest that time in the natural environment promotes prosocial behavior and builds social capital. Finally, parks and green spaces strengthen environmental health as measured by air quality and climate adaptations, such as temperature (including urban heat island effect) and the impact of adverse weather-related events on communities. As natural infrastructure, they encourage disaster planning and social resilience by fostering neighborhood connections and community ties, particularly following a disaster. These environmental health benefits can in turn generate other health benefits (e.g., improved air quality leading to reduced incidence and severity of juvenile asthma). A variety of tools and metrics are currently used to quantify some of these health benefits, but nothing robust exists for the field that combines all four health dimensions. Additionally, although the park equity research is strong, fewer studies focus specifically on linking the health benefits of equitable access to parks with their economic impact. In this report, we review a few of the more prominent tools available for park leaders and advocates and examine methodologies for measurement, including hedonic modeling, benefits transfer, and benefits tools. The existing research presents several key takeaways that need to be considered when estimating the health benefits of parks: 1. The literature is strongest in connecting the quantifiable value of parks for physical activity and physical health impacts and the value of green space for mental health well-being and environmental impacts. 2. Disentangling the actual causal relationship between parks and outcomes is challenging given the number of other factors, the variation in methodologies, and the range of characteristics different parks present. 3. Although individual- and even community-level impacts are moderately well understood, additional research is needed to understand the connection between parks and larger health systems. These considerations and opportunities for future research notwithstanding, the existing and growing body of research provides a sufficient foundation from which to estimate the health benefits of
vii i EXECUTIVE SUMMARY equitable access to quality parks. The challenge for researchers and communities is to identify a workable tool that considers this nuance while producing estimates of parks’ benefits that are meaningful, clear, and sufficiently rigorous. Additionally, policy and practice solutions have to consider quality and access, urban versus nonurban contexts, park or green space size, and perception and actual safety. Park leaders, advocates, and allies can build from this framework to demonstrate how parks and green spaces are more than “nice to have” amenities; rather, they should be considered critical civic infrastructure that can promote equity for communities.
THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS 1 Introduction Green space is critical for outdoor physical activity and a key driver of improvements in overall physical health. Proximity and exposure to trees and greenery can promote mental health by providing psychological relaxation and stress alleviation. At the community level, parks can contribute to disaster recovery and resilience planning and provide several environmental benefits. Additionally, parks foster opportunities for individuals to gather, connect, and socialize with their neighbors and other park users. The COVID-19 pandemic has underscored the importance of accessible green space in a way that no event has before. Parks have played a critical role in supporting mental and physical health and have provided essential space for social gatherings and community events. Parks have a substantial impact on health equity. Parks are often the only free, publicly accessible areas for physical activity. In communities with limited access to places to walk, roll, and bike safely or to amenities such as gyms or private green spaces, many of the health benefits associated with physical activity are only accessible through parks and public green spaces. In some urban spaces, parks and planned green spaces can also serve as an access point to nature, which can promote restfulness and improve mood. However, not every household has equal access to quality green spaces, and in fact, access is often constricted along racial and socioeconomic lines. Formerly redlined2 communities have the least access to green space (Nardone et al. 2021). Data show that parks in Black and brown neighborhoods are smaller in size and are more crowded (Trust for Public Land 2020). Lack of economic resources, racism encountered in park space, policing of park spaces, historical racial covenants, current segregation patterns, and placement of Black and Brown communities have all limited access to park space for people of color (Scott and Lee 2018; Yañez et al. 2021). Ensuring that all people are able to use and enjoy safe, quality, and accessible green space will mean dismantling systemic barriers that prevent some from feeling welcome. This research summary will explore the evidence for health benefits associated with parks and green space. But evidence suggests that these health benefits cannot be untangled from issues of access and equity. The research reviewed will focus not just on what health benefits exist but also on who is able to access them and how can that access be made more equitable. The burgeoning “park justice” movement is highlighting the idea that to build a beautiful, engaging park is by itself not enough. To develop equitable, quality parks, policymakers and local leaders must confront the systemic disinvestment embedded in the history of these spaces. These policies and practices have entrenched
2 THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS the stark opportunity gaps for Black and brown people, preventing them from receiving the many benefits of parks. BOX 1 Studying the Health Equity Impacts of Parks This research summary is the first step in a larger project commissioned by the National Recreation and Park Association to understand and communicate the economic impacts of local parks based on their health benefits. The goal of this work is to better equip local park and recreation professionals and advocates with the evidence to make a health-based case for the value of parks. We hope this research will also inform efforts to make parks more accessible and equitable so that the health benefits accrue to the entire community and all park users. An advisory committee composed of park and recreation professionals, health experts, and equity experts are informing the work, and the project will culminate in an adaptable and practical tool for measuring the health equity impacts of parks at a local level.
THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS 3 Methodology We used a snowball sampling strategy to identify documents for review. We began with a set of 15 key documents from the National Recreation and Park Association’s (NRPA’s) extensive existing reports on parks, green space, and health, as well as 15 documents identified as critical pieces of literature by the Urban team. From this initial sample, we expanded our review to examine citations from these sources as well as papers that cited them. We sought to include not only academic literature but also practitioner reports and guidance documents from the field. From the initial set of documents, we identified where there were gaps in the literature. We used keyword searches to pull in additional documents focused in the four topic areas (physical, mental, social, and environmental health). From that body of literature, we focused on documents published between 2000 and 2021, with exceptions for a few key sources. We concluded with 102 reference documents that include journal articles, practitioner documents, and book chapters sourcing quantitative analyses, secondary data reviews, literature scans, surveys, case studies, toolkits, and other methodologies. We discussed our preliminary findings and methodology with experts from the field through the NRPA advisory committee, NRPA staff, and senior Urban advisors. These perspectives helped supplement our research review by grounding the findings and strengthening our process. BOX 2 Terminology Park An open outdoor space. Incorporates amenities such as playgrounds and courts as well as green space. This document will refer exclusively to public parks unless otherwise noted. Used jointly with green space within this document; where we mean parks specifically, it will be noted in the text. Green space Land that incorporates greenery such as grass, tree cover, shrubs, etc. This document refers to publicly accessible green space unless otherwise noted. At points in this document, the research will refer to specific types of green spaces (e.g., tree cover). Used jointly with parks within this document; where we mean green space specifically, it will be noted in the text. Access
4 THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS Encompasses multiple measures of the usability of parks and green space. Proximity, density, quality, safety, and amenities are all measures of park access. Equitable park access focuses on eliminating barriers along these measures for all potential park visitors. Note: Terminology is based on MacCleery, McConville, and Hammerschmidt (2021).
THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS 5 Park Characteristics Parks and green spaces affect health outcomes in many ways. Understanding their impact on health requires an understanding of the variety of parks and park contexts. Park size, quality, amenities, and composition all have implications for how parks affect health. Whether the park is rural or urban, is easily accessible or difficult to access, or includes amenities that the surrounding community desires are important inputs to any analysis of the health impact of park space. These factors can change who reaps the benefits of park spaces, how those benefits accrue, and level of the impacts. A substantial amount of literature is available on accessibility and amenities in parks and how those factors affect outcomes such as physical activity, and the body of literature on the racial and economic disparities in park access is growing. In other areas, such as mental health impacts or environmental impacts, there is less focus on the park context. As this document reviews the literature on health equity impacts of parks, keep in mind that the park context described in the research might impact the findings. Quality and Accessibility Access to high-quality park space in the United States is inextricably tied to the country’s history of racism and white supremacy. Many of the health benefits we will discuss are contingent on community access to park space and on the quality of that space. Unfortunately, park spaces are inequitably distributed. Policies, procedures and decisions for parks and green space have been designed to concentrate quality parks and park programming in predominately white and higher-income neighborhoods, leaving people of color and low-income residents lacking the same quality of amenities as white people (Yañez et al. 2021). Research comparing present day green space with the Home Owner’s Loan Corporation maps that formed the basis for redlining show that formerly redlined areas have less green space (Nardone et al 2021). Using propensity score matching, Nardone and colleagues (2021) controlled for other demographic and economic factors and compared areas one grade apart. They found a statistically significant decrease in green space as grades decreased. This research builds on prior evidence connecting the legacy of racism and segregation with lack of access to urban green space and urban heat islands. One study found that formerly redlined areas have less green space and more nonpermeable surfaces and are on average 2.6° C (36.68° F) hotter than nonredlined areas (Hoffman,
6 THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS Shandas, and Pendleton 2020). Similar associations appear in research about racial equity and park quality. An analysis using park audits found that as a neighborhood’s share of people of color increased, the number of disamenities (e.g., dangerous spots, excessive litter, waste and noise, poor maintenance, vandalism) in parks increased and amenities (e.g., benches, trails, drinking fountains, and lights) decreased (Hughey et al. 2016). The conversation about racial equity in park access is critical because research has suggested a link between measures of park access (proximity to parks and park quality) and higher rates of park use and physical activity. Park proximity can be measured by distance to the closest park or by amount of park space in the surrounding area. Park quality is a more subjective measure, but the Urban Land Institute offers five criteria for considering park quality; their framework measures whether a park is wellmaintained, accessible, well-programmed, relevant to community, and flexible (MacCleery, McConville, and Hammerschmidt 2021). Considering park congestion level (i.e., number of people per park acre if each person were to utilize the nearest park) is also important in framing who has quality access. Research shows that Latinx Americans, and to some extent Black Americans (including lower-income householders) were most likely to live closest to congested parks (Wolch et al. 2014). This correlation is driven in part by which neighborhoods people of color tend to live in. Some debate exists within the literature about the impact of self-selection on where a person chooses or is able to live, but proximity to park space remains a key driver of park access. The literature is inconclusive about whether distance to nearest park space or density of surrounding park space has a more significant effect on physical activity; both have been associated with higher park use and physical activity (Kaczynski and Mowen 2011; Mackenbach et al. 2018). This correlation holds true even among those who put low importance on park space (Kaczynski and Mowen 2011). A survey of Kansas City, Missouri, households found a significant relationship between self-reported use of park space for physical activity and the amount of park space within one mile (diversity of park amenities was also associated with higher rates of use; see Kaczynski et al. 2014). Interestingly, distance to closest park space was not significantly associated with use. Empirical evidence suggests that perceptions of park quality are positively associated with park use and subsequently with higher rates of physical activity among those with positive park perception (Bai et al. 2013). This association is also present among youth; a study in Baltimore among predominately Black high-school students showed a positive effect for self-reported perceptions of park quality and availability on park usage, with a more tenuous link between perceived availability and physical activity (Ries et al. 2009). Several quasi-experimental studies have suggested that making improvements to
THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS 7 park features and amenities is associated with an increase in park usage for both youth and adults (Heath and Bilderback 2019; Veitch et al. 2012). Urban versus Rural Much of the literature on the effects of parks on health tends to focus on urban and suburban areas. Because of the nature of urban development, access to unplanned green space is limited, necessitating the intentional creation of park space. This leaves several gaps in the literature on the impact of parks and green spaces. First, the term “urban areas” encompasses a broad range of cities based on region, geographic size, and population. Further, it can encompass areas that might be colloquially considered suburban. Smaller cities may lack the funding for parks that larger cities are able to marshal, but larger cities may face distinct gentrification pressures and rapidly changing neighborhood demographics (Eldridge, Burrowes, and Spauster 2019). The inequities in access to quality park space may also align with urban/suburban divides. Parks in dense center city areas have considerably less acreage per person than more suburban areas (Rigolon 2016). These center city parks were also more likely to be in predominately Black neighborhoods, although patterns of gentrification complicate efforts to use set neighborhood definitions. Further, research focused on urban parks may not be directly applicable to parks in rural areas. Observational evidence suggests that rural parks may be utilized differently than urban ones, with visitors in rural areas more likely to engage in sedentary activities and less likely to be engaged in moderately vigorous exercise (Roenmich et al. 2018). A survey of residents in rural Iowa found a statistically significant relationship between feelings of access to recreational and walking space and community satisfaction overall (Payne and Schaumleffel 2008). But conflicting evidence from a survey of California youth suggested that perceived park quality and access is correlated with physical activity among urban youth but not rural youth (Babey et al. 2008). Similar to urban areas, rural areas are diverse and have a multitude of differing characteristics. Comparative analyses or typologies of rural areas as they relate to parks and green spaces are a gap in the literature.
8 THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS Size of Park or Green space Early conversations with the advisory committee identified park size as a potentially important component to contextualize park impact. As referenced previously, dense urban areas are more likely to feature smaller parks with fewer amenities. Communities might use smaller parks differently from larger ones in ways that might affect health benefits. There is evidence that larger parks with more amenities may have a more direct impact on physical activity (Kaczynski, Potwarka, and Saelens 2008). Beyond the connection between quality and diversity of amenities and usage, there is little research specifically on small urban park spaces. One study using survey data on residents near pocket parks found a similar positive effect on physical activity for these small parks as larger neighborhood parks (Cohen et al. 2014). Other research is largely observational, noting the types of usage for small parks. One study used observation and follow-up surveys to classify how users were engaging with small parks. The most common uses were either socializing (31 percent) or resting (31 percent). A study using images of small parks to gauge perceived likelihood for restoration (positive impact on mood) found that the share of ground surface covered by grass, visible tree cover, and park size were most correlated with restorative impact (Nordh et al. 2009). This anecdotal evidence suggests smaller parks may retain some of the positive impacts on mental health and well-being and social connectedness of larger parks, but additional research is needed to clearly delineate the impact of small parks and green spaces. A much smaller body of research focuses on trails and has shown similar physical activity benefits for proximity to trails relative to parks and other green spaces. Particularly in rural areas and smaller towns, trails have been associated with increased physical activity (Abildso et al. 2012; Brownson et al. 2000). Evidence suggests that length of trail and material (i.e., pavement) have the most significant impact on use (Brownson et al. 2000). Safety in Park spaces Parks and green spaces generate more benefits when they are accessible and usable and when users have a general sense of safety. When parks are perceived as unsafe, users miss out on the positive outcomes of green spaces (Williams et al. 2020). Research shows that parks that are well maintained are safer, encourage community building, and promote civic trust (MacCleery, McConville, and Hammerschmidt 2021).3 Parks can drive safety by being welcoming community assets and public spaces, providing calm, and reducing crime (Burgess et al. 1988; MacCleery, McConville, and Hammerschmidt 2021; NRPA 2019). The larger the number of park users, the lower the number of
THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS 9 antisocial and unsafe behaviors (Citizens’ Taskforce on the Use and Security of Central Park 1990). People increase their use of parks the safer and more welcome they feel, which evidence shows is impacted by park design, the presence of trees, and inclusiveness for multiple demographics. People's perceptions of safety and their willingness to use a space can be affected by the design and maintenance of a park. It is well documented that the urban and architectural design of built and natural environments that maximize visibility, encourage activity, and improve accessibility can reduce crime and the fear of crime (Stanley 1977). The distribution of amenities such as lighting, call boxes, signage, and other features can eliminate deserted areas and reduce senses of loneliness (MacCleery, McConville, and Hammerschmidt 2021). Further, lack of maintenance contributes to the perception of unsafety. The presence of garbage, damaged equipment, and damaged trees deter park users, and on a 2020 survey, respondents did not feel safe visiting parks with these concerns (Lopez, Kennedy, and McPhearson 2020). Understanding this relationship, New York City’s Park Inspection Program conducts audits to determine the condition of these features, and the Parks Without Borders program targets strengthening safety through maintenance. Similarly, the Metro Action Committee on Public Violence Against Women and Children, based in Canada, has implemented a safety audit procedure to monitor and correct safety concerns in parks. Even landscaping, such as trees with higher canopies and features that reduce blocked sections of the park, can contribute to an improved perception of safety (MacCleery, McConville, and Hammerschmidt 2021). Parks often provide large concentrated areas of greenery, which have positively contributed to community and individual public safety. As demonstrated in Chicago, an increase in tree canopy can result in a decrease in neighborhood crime rates, particularly for violent crime (Schusler et al. 2018). In a later study in Chicago (Herrnstadt et al. 2021), researchers found that tree canopy can improve air quality and general physical health through a causal link between air pollution and violent crimes. But design and landscaping alone cannot address the challenges of safety in parks (Zavadskas et al. 2019; NRPA 2019). Strategies for improving safety include removing barriers to access both physical and mental (e.g., isolated spaces, limited entry points, and perceptions of unsafety) that prevent users from feeling welcome. Parks must appeal to a wide diversity of users, including people of color, youth, seniors, varying abilities, and LGBTQ+ people to be safe and accessible (MacCleery, McConville, and Hammerschmidt 2021; NRPA 2019).
10 THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS Physical Health Connections between Parks and Physical Activity Park access is associated with increased levels of physical activity across several studies. Evidence shows that proximity to and use of parks, green space, and tree cover are all correlated with greater levels of physical activity (Eichinger et al. 2015; Pretty et al. 2005). Studies of physical activity have emphasized that park density (the amount of park space in proximity) is highly correlated with physical activity (Roemmich et al. 2018; Roux et al. 2007; Wendel-Vos et al. 2004). An analysis in New York City, NY; Baltimore, MD; and Forsyth County, NC, found that when analyzing individual survey respondents by density of nearby park space at 1-mile, 2-mile, and 5-mile radii, those in the highest quartile of park density were significantly more likely to engage in physical activity (Roux et al. 2007). Amount of park space in proximity has been shown to have a significant positive relationship with physical activity among youth (Epstein et al. 2006; Veitch et al. 2012; Yi et al. 2021). A longitudinal analysis that followed impact on physical activity among a cohort of youth showed that the magnitude of this relationship lessens as youth age (Yi et al. 2021). Strong evidence suggests recreational programming and outreach and communication activities have significant impacts on usage and rates of physical activity in parks. Rigorous research on the impact of marketing training for park staff and funds for outreach shows that dual approaches that combine park improvements and outreach campaigns have a significant impact on physical activity in parks and green spaces (Cohen et al. 2013; Hunter et al. 2019). A meta-analysis of quasi-experimental studies found that in each study of the impact of parks and green space, this dual approach yielded statistically significant increase in park use and physical activity (Hunter et al. 2019). Qualitative studies have corroborated the quantitative evidence (Mccormack et al. 2010). Focus groups conducted among park users in Perth, Australia, indicated that proximity and accessibility of park facilities were important factors for physical activity (Giles-Corti and Donovan 2002). Qualitative research focusing on Latinx, Black, and immigrant populations all indicated that their proximity to park space, their ability to access park space without driving, and greater density of their surrounding parks improved their ability to engage in physical activity (Griffin et al. 2008; Ries et al 2008; Roux et al. 2007).
THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS 11 Some studies have found a connection between access to leisure time and perceived neighborhood safety and physical activity in park spaces (Eichinger et al 2015). However, other research has found no direct connection between perceived or objective measures of crime and physical activity in parks (Ries et al. 2009; Zhang et al. 2019). This suggests that additional evidence is needed to understand the connection of neighborhood conditions and physical activity in parks. Physical Activity and Health Outcomes Research on the connection between physical activity and health has consistently found strong positive associations. Physical activity is correlated with a range of impacts on cardiovascular health, including reduced risk of cardiovascular disease and reduced risk of mortality because of disease (Myers et al. 2004; Warburton, Nicol, and Bredin 2006). Physical activity has been shown to reduce risk of mortality from all causes among men, women, and the elderly (Bijnen 1999; Myers et al. 2002; Oguma and Shinoda-Tagawa 2004). In one study of exercise habits in men, tests associated exercise with a 50 percent reduction in risk for cardiovascular disease (Myers et al. 2004). For those with existing cardiovascular disease, activity has been shown to reduce or attenuate effects of the disease (Warburton, Nicol, and Bredin 2006). Physical activity has been shown to affect several additional health outcomes, including reductions in incidence of type 2 diabetes, with particularly strong impacts among those at highest risk (Helmrich, Ragland, and Paffenbarger 1994; Manson et al. 1992). One study associated moderate exercise with a reduction in diabetes incidence of 40 to 60 percent over three to four years for high-risk populations (Williamson, Vinicor, and Bowman 2004). Physical activity has similar effects on cancer incidence, particularly colon cancer, which is associated with a 30 to 40 percent reduction, and breast cancer, which is associated with a 20 to 30 percent reduction (Kampert et al. 1996; Lee 2003; Sternfield et al. 2009) Just as physical activity conveys several health benefits, inactivity is associated with several negative health outcomes. A number of estimations at the national level and across countries have suggested the costs of physical inactivity are significant and include increased rates of noncommunicable disease and corresponding health care costs and lost life years (ISCA and CEBR 2015).
12 THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS Health Impacts of General Park Usage and Green Space Beyond the connection of parks and physical activity, usage of park services is associated with reductions in various negative health outcomes and illnesses. Spending even 120 minutes in green spaces has been associated with higher levels of reported good health and well-being (White et al. 2019). Evidence has associated time spent in parks and green spaces with reductions in complications caused by chronic diseases such as diabetes and heart disease (Bowler et al. 2010; NRPA 2015). Evidence from a large-scale Dutch survey suggests that proximity to green space has a positive effect on self-perceived general physical health, with a larger effect for the elderly, youth, and families with low incomes (Maas et al. 2006). A significant body of evidence supports the connection between park and green space and children’s physical health. A study using survey data of Latinx children in Houston, Texas, found that those living in areas with a higher density of tree cover had lower levels of obesity and a higher healthrelated quality of life (Kim Lee, and Sohn 2016). Similar studies using survey data of children found that park space had a more significant impact on health for urban and suburban children than for rural children (Tillmann, Clark, and Gilliland 2018).
THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS 13 Mental Health Mental Well-Being A wealth of research connects parks with positive effects on individual mental health well-being. Time spent in green space has been associated with improved mental health outcomes, including reduced stress levels (Capaldi, Dopko, and Zelenski 2014; Gidlow et al. 2016; James et al 2015; Roe et al. 2013). Evidence suggests that time spent in green space has a positive impact on general mental well-being and self-reported happiness (Capaldi, Dopko, and Zelenski 2014). Research using data from the RESIDential Environments Project in Australia suggests that proximity and density of green space is associated with positive impacts on mental health (Wood et al. 2017). Physical activity is associated with improvements to measures of health such as mood and selfreported well-being. One study compared participants who exercised while viewing images of nature with who exercised without such exposure and found that the benefits of activity are stronger when in or viewing natural surroundings (Pretty et al. 2005). Interestingly, follow up studies with children and adolescents replicated the impact of exercise on mood, but there were no additional effects of exercise in either green space or while viewing natural environment images (Reed et al. 2013; Wood et al. 2013). In a large-scale survey of people registered across 104 entry points into the medical system, proximity to green space was associated with higher self-reported general health. This relationship was stronger for lower income groups, as well as the elderly, youths, and people with secondary education (Maas et al. 2006). There is some evidence that the effect of parks on mood and happiness might be mitigated by the context the park is in. A study of parks in Singapore found that there was no significant connection between parks and increased happiness (Saw, Lim, and Carrasco 2015). This study, though hardly challenging the broader literature that supports the link between mental health well-being and park space, suggests that additional research is needed on how the link might be affected by different contexts.
14 THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS Use of Mental Health Services Some evidence suggests green space influences the usage of mental health services. Parks and green space have been noted as important parts of a well-functioning mental health system (Buckley and Brough 2017; Hosie et al. 2015). Communities with higher levels of green space and tree cover have lower usage of mental health services and treatments, controlling for demographics and economic status (Nutsford, Pearson, and Kingham 2013; Taylor et al. 2015). An analysis of street tree coverage in the United Kingdom associated a per unit increase in trees per km of street with a decrease of 1.18 prescriptions per thousand population, a relatively small but significant relationship (Taylor et al. 2015). A study of green space density and proximity and anxiety/mood disorder treatments across 3,149 small-area units (similar to census blocks) in New Zealand indicated that both green space measures were associated with fewer treatments (Nutsford et al. 2013). There is extensive research on the economic impact of reducing mental health service use (Hosie et al. 2015; Lambert et al. 2015),4 so these findings, although not conclusive, could have implications for the economic health equity benefits of park spaces. In Buckley and Brough’s (2017) review of the literature connecting parks and mental health, they offer a framework for evaluating economic value of parks on mental health. The framework includes three pathways that might yield economic mental health benefits: reduction in mental health service use, increases to productivity, and reductions in antisocial behavior. Functioning and Productivity As people experience poor mental health and general stress, their productivity is also affected. The literature available for review focuses on occupational stress and productivity, but these factors also likely affect personal productivity (Sauter and Murphy 1995). Several international studies have linked access to green space, whether through physical presence or views, to reduced stress levels. A study of office workers in Seoul, South Korea, found that those who had natural view from their windows had lower stress levels and higher job satisfaction. A case study in Belgrade, Serbia, found that the installation of a park within a business district had a direct impact on stress relief. The frequency, duration, and activity of open space usage reduced the stress levels and stress-related experiences of employees in the workplace as recorded by a self-reported questionnaire. Open space, including greenery and outdoor space, fostered overall improvements to employee health and well-being (Maric et al. 2021).
THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS 15 Social Health Social Cohesion Social cohesion refers to the social connections that exist among community members and how connected an individual feels to others (Kawachi and Berkman 2000). Social cohesion provides social benefits in terms of community connectedness but is also associated with other health benefits such as reduced levels of depression (Perez et al. 2015). Conversely, social isolation is associated with a number of negative health outcomes, such as being less healthy overall and being more susceptible to stress, depression, and cardiovascular issues (Jennings and Bamkole 2019). Evidence suggests that parks have a positive effect on social cohesion and sense of belonging (a critical measure in surveys of social cohesion), and engagement with park spaces can facilitate attachment to communities (Peters, Elands, and Bujis 2010). A cross-sectional study of the RESIDential Environments Project surveyed 911 residents in Perth, Australia, using a survey based on the 12-item Sense of Community Index (an established survey instrument measuring connection to community) and found that the perceived quality of public open spaces was positively associated with higher community attachment (Wood et al. 2017). Parks are also connected with increased levels of social engagement (Jennings and Bamkole 2019; Kaźmierczak 2013). There is some evidence that multiethnic interactions in public spaces, such as parks, yield benefits to social cohesion in diverse areas (Perez et al 2015; Peters 2010). A multimodal analysis of five urban park spaces in the Netherlands involving a survey and observations and interviews found similarities in park usage across ethnic groups and that urban parks facilitate interethnic interactions (Peters 2010). A study comparing the impact of vegetation levels in neighborhoods with park space found that general vegetation was positively correlated with reduced stress but negatively correlated with social support, as measured by self-reported surveys (Fan et al. 2011). Park spaces, however, were significantly correlated with positive impacts on both measures, suggesting that programmed park space may have a greater impact on overall health than general levels of neighborhood vegetation (Fan et al. 2011).
16 THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS Social Capital If social cohesion is the degree to which a community is connected, then social capital is the access to resources and ability to act socially and effect change (Putnam 1993). Natural environments have been shown to impact social actions. Participants in a study of college students who were shown natural environments were more likely to engage in cooperative and prosocial behavior in subsequent game testing (Zelenski 2015). How parks are activated has a significant impact on their contribution to social health. Environmental education programs, volunteer programs, and community-led stewardship are associated with increased levels of social capital (Krasny et al. 2015). Urban parks can serve as an access point to social participation through nature-based recreation that might otherwise be inaccessible, particularly to people in lower-income neighborhoods (Baur and Tynon 2010; Graham and Glover 2014).
THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS 17 Environmental Health Air Quality Urban parks have an established impact on air quality. Urban areas generally have lower air quality than surrounding areas; one study put the disparity at 5 to 25 times more gaseous pollutants (Heidt and Neef 2008). As a major source of tree cover in urban settings, parks have a role in removing pollutants from the air and sequestering carbon (Paoletti et al 2011). The storage of carbon alone has been estimated to have a $2 billion impact in urban areas (Nowak et al. 2013). A study in the Taipei metropolitan area shows that higher green space density (aggregating green space) has demonstrated reduced air pollution. Lower emissions influence the microclimate, such as through cooler temperatures and smaller distributions of rainfall (Liu and Shen 2014). Although the evidence supports the finding that urban green space and tree canopies improve air quality overall, the literature is less unanimous on the direct impact of tree coverage on asthma. Some evidence suggests a limited impact of park space on rates of environmentally sensitive health conditions such as asthma and suggests that prevalence of tree cover may be associated with higher allergy prevalence (Lovasi et al. 2013). Using data from a birth cohort of Black and Dominican children in New York City, they found a positive connection between tree canopy coverage and asthma rates (Lovasi et al. 2013). However, literature examining the value of a “green prescription” by comparing the tree canopy with rates of health conditions found a limited but significant relationship with lower rates of asthma (Ulmer et al. 2016). There is a relationship between exposure to air pollution and higher cardiovascular mortality and an association between green space and a reduction in air pollution. However, studies mostly examine how green space at varying densities can reduce cardiovascular risk factors; links between the size of green space, time spent in green space, improvements to air quality, and cardiovascular physiology are more tenuous (Lanki et al. 2017; Plans et al. 2019; Seo et al. 2019). Climate Adaptations Climate change has impacted the environment across geographic areas. Urban areas have experienced a well-documented increase in temperatures (McPherson 1994; Whitford, Ennos, and Handley 2001).
18 THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS This effect has been exacerbated by densification as cities have more impervious surfaces and less greenery to provide shade and absorb heat (Heidt and Neef 2008; Myint et al 2010). As temperatures rise in urban areas, so too does the demand for, and cost of, electricity, with some 5 to 10 percent of electricity demand related to increased urban temperatures (Akbari, Rosenfeld, and Taha 1990; Akbari, Pomerantz, and Taha, 2001). The presence of a developed tree canopy can counteract some of the temperature increases caused by this urban heat-island effect (Akbari, Pomerantz, and Taha 2001). Additionally, decreasing the amount of impervious surface area (e.g., pavement) and increasing the amount of grassy and vegetative surfaces can contribute to decreases in temperature as well (Taha 1997). A case study of four sites in Merseyside, UK, found that among several indicators of ecological performance (surface temperature, carbon sequestration and storage, hydrology, and biodiversity), more affluent areas performed better across each indicator because of higher quantities of green space and tree cover (Whitford, Ennos, and Handley 2001). Critically, much of this literature looks at urban green space broadly, including public and private spaces. Climate change has also led to an increase in the numbers of adverse weather events. Thus, discussion has increased about mitigation and adaptation to reduce the risks associated with such events. Parks and green spaces can serve as natural ways to increase urban hazard resiliency. Green space can serve a crucial role in protecting against flood risk by reducing runoff. Case studies of parks that act as natural infrastructure show that these spaces can improve water filtration and curb runoff (Chadsey and Grenfell 2020). Surfaces such as pavement and gravel do not absorb water, whereas soil, grassy areas, and wetlands act as natural absorbent materials for runoff water during storms (Depietri, Renaud, and Kallis 2012; Taha 1997). Disaster Planning and Social Resilience Public green space is critical for improving environmental health but can also support building more socially resilient communities as they foster social connections and neighborhood ties, which are particularly key for disaster planning and recovery. Research examining the psychological connection humans have with nature after a natural disaster finds that people seek resilience through green spaces (Campbell et al. 2016; Tidball 2012). Disasters cause physical damage but also cause psychological damage and trauma, strain social connections, and damage livelihoods. Faced with increased social and psychological strain, emerging research indicates people seek out parks and green spaces as restorative resources (Campbell et al. 2016; Wolf and Rozance 2013). As the COVID-19 pandemic has
THE HEALTH BENEFITS OF PARKS AND THEIR ECONOMIC IMPACTS 19 demonstrated, parks and green spaces allow people to build community and strengthen social structures for disaster relief and recovery (Campbell et al. 2016; Slater, Christiana, and Gustat 2020; Wolf and Rozance 2013). Studies reinforce that following a disaster, communities with strong social ties and connectedness demonstrate pathways toward community recovery (Wolf and Rozance 2013). The literature on the connection between green spaces (including parks) and psychological and social disaster resilience is mostly grounded in research on the psychology of environment, research on responses after specific disasters, and research attributing the inherent value of nature as refuge in a general context. A mixed-methods study of New York City parks following Hurricane Sandy demonstrated that although the social and environmental benefits of parks are clear, there is limited understanding of how these benefits affect non–park users following a disaster (Campbell et al. 2016). There may be opportunities to measure some sociocultural impacts, such as spiritual and religious value, aesthetic value, and recreation and ecotourism (Millennium Ecosystem Assessment 2005). But there are several other social resilience benefits that are harder to quantify, and the literature has not adequately assessed these measures. For instance, few social impact assessments include a resilience framework, and other metrics often focus on global or community-level benefit instead of individual well-being (Campbell et al 2016).
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