To create a platform for student research on sustainability as well as to showcase the diverse and robust knowledge of the Student Environmental Action League members we’re beginning to showcasing research papers authored by our membership! If you’re interested in having some of your work email your paper to firstname.lastname@example.org or reach out to us on Facebook!
“Urban Green Space as a foundation for Cognitive, Psychological, Behavioral, and Physical Health”
By :Sarah Quirk
Urban green space, defined as gardens, parks, and recreational areas, has been made a focus of city planners, leadership, and sustainability professionals. Traditionally, the value of green space, and the argument for its urban installation, has been rooted in its benefit for stormwater remediation and retention, air quality, and the urban heat island effect. A growing body of science, however, is showing how regular interaction with the natural environment is connected to many other components of public health. Studies have shown that childhood development, mental health, and crime rates are all Public Health factors impacted by the presence of extensive green space, and that those with lowest socioeconomic standing are often impacted the most. As cities are encouraged to develop resiliency and adaptation efforts for climate change, we can expect to see green space creation a more common occurrence. In development of resilience climate action plans, community green space should be required in all neighborhoods, because it promotes the psychological, cognitive, physical, and behavioral health of the community.
Psychological health relates to an individual’s view of oneself and others, maintenance of relationships, and ability to show resiliency to stress and pain. In this research paper, it’s most represented by mental health, and related disorders. A study in the Netherlands has shown a negative correlation between clusters of disease prevalence in cities and neighborhoods, and existing green space6. It was identified that the largest impact of green space within one 1 kilometer of a home was on the mental health of low-income children. Anxiety disorder and Depression showed the strongest relationship between reported prevalence in a population, and relative distance to green space, which led researchers to believe that there is a correlation between an individual’s likelihood of exhibiting mental illness, and their domestic exposure to the natural environment.6
Another study, conducted in New Zealand, showed similar results. Using GIS technology to quantify greenspace, and anxiety and mood disorder treatment counts within small areas of the city of Auckland, a relationship between the two was shown. Less distance from useable green space (parks, fields, and public gardens) and the home, and a greater proportion of total green space in the area, was associated with less anxiety and mood disorder treatment, standardized across several age groups 4 . (See Table 1 in the Figures and Graphics Section for correlation data.) Simply, the more green space, and the closer it was to residents, the less likely they were to experience these mental illnesses.
There are several theories for why and how psychological health is impacted by exposure to the natural environment. One theory states that green space offers a place for increased social interaction amongst residents and citizens,8 whether by recreation, socializing and connecting, aesthetic enjoyment, or physical exercise. Many of these elements can impact psychological health- in most cases, in a positive way. More related to general well-being and health, it is also noted that mental illnesses can be the antecedent to other physical illnesses and chronic conditions.4 For this reason, psychological health ought to be prioritized from a Public Health standpoint, to increase intervention opportunities from other unhealthy drains on a community from occurring. These studies show that increased green space availability may be an effective intervention tactic.
The physical health, that of the human body and parts within in, of a community is also positively impacted by more ubiquitous green space, and not for the reasons commonly thought. A common philosophy in urban studies (of deviance and poverty) is referred to as the “Broken Window Theory,” used when discussing systems of habit and culture within urban environments. This theory relates to the perceived value of specific areas, and how that value impacts the behaviors of those within it. Often, more dilapidated and broken-down neighborhoods, with observable damage to structures and infrastructure, are more likely to be further degraded. Researchers hypothesize that this occurs because criminals feel bolstered by environments lacking rules or order; that others are less likely to step in and protect areas they have no ownership over, and their destructive acts won’t receive consequences.1
A study spanning almost ten years (1999-2008) in Philadelphia monitored the continuous greening of vacant lots in the city. The data showed that greening areas had led to a drop in crime, specifically gun-related, in the immediate vicinity.1 Here we see how green infrastructure and lands can impact the safety of citizens in urban environments, and the safety of the city as a whole. In and around newly-greened lots, gun assaults and vandalism decreased over the decade, which researchers attribute to the increase in perceived quality, and assumption that tending to, and supervision of, the green space was occurring. They also note that vacant lots were commonly used by criminals to anonymously dispose of guns and other weapons, and by greening them, this option was no longer preferable.1
Air pollution is a well-known safety hazard to the health of urban residents. In one study, the impact of green environments at home and school was measured in primary-school students in Spain.2 Negatively correlated to presence of natural environments, specifically trees, was the amount of air pollution students were exposed to. A measurement of over 2,500 students indicated that those exposed to more air pollution (specifically in the forms of elemental carbon and nitrogen dioxide) showed a lower level of memory growth, and attentiveness, throughout a 12-month period than their counterparts.2 (See Figure 1 below.)
Another benefit to the expansion of green space in cities is the habitat creation for local, seasonal, and ubiquitous wildlife species. Specifically, natural landscapes are refuge for more microbial diversity, including microorganisms which are critical to our human health. Microbiologists and biological scientists have written and studied the health impacts of exposure to micro and macro organisms in nature, and the specific advantage it offers children through immunoregulation development.7 A study also suggests that children in Westernized populations have less exposure to these organisms, which can build up and work with, our human immune systems. The long-term impact of this deprivation takes the form of chronic conditions, childhood brain development, cardiac deficiency, psychiatric problems, and premature deaths.7 Children, and people of all age, have a lot to benefit from more exposure to nature and ecosystems, through stronger resiliency to disease and other conditions.
Most risks discussed in this paper are related to their average impact on a community of people. However, it must be highlighted and emphasized that, in almost all cases, the percentage of studied populations with the lowest income are often who suffer most acutely, and most often, from their environment. One study focused on these health inequalities, finding that residents living in the greenest areas had the lowest difference between health inequality and income deprivation- simply, areas promoting green space were most effective in impacting “socioeconomic health inequalities” 3 (see Figures 2 and 3 below.)
Green space and exposure to nature has the power to positively influence our well-being, through our behavioral health, which is described as the “connection between our behaviors and the health and well-being of the body, mind, and spirit.” 9 In almost all studies, behavioral health was analyzed by the presence or lack of stress in the daily lives of residents.
Researchers suspect that green spaces can be areas of recuperation and relaxation from taxing activities, allowing the body’s levels of cortisol in the blood to lower.1 Cortisol is the hormone released by the endocrine system into the body when threats are perceived by the brain. It’s historically been beneficial and necessary when the body enters “fight or flight” mode- by suppressing the digestive system, increasing blood sugar and the brain’s use of glucose, and increasing blood pressure, among many other things. However, when the body is in a constant or semi-constant state of stress, referred to as chronic stress, continuous release of cortisol in the body can alter many systems of the body, and compromise the immune system. Chronic stress, along with other chronic disorders, can jeopardize long-term health and susceptibility to further disease.
In Philadelphia, greening of abandoned lots led residents to report significantly less stress, paired with an increase in exercise within newly renovated neighborhoods.1 A study in Scotland measured salivary cortisol levels in deprived urban neighborhoods, with the goal of determining average stress levels per distance to green space. Their findings highlight that those living in areas with more useable green space typically experience less stress, and the opposite for those living without. By measuring circadian cortisol levels, researchers were able accurately predict cortisol levels and cycles in residents, based on their gender and location in the neighborhood. Interestingly, women experience more perceived stress than men, even when their accessibility to green space was equal 5 (See Tables 2 and 3 below.)
Most importantly, this study identified that women with little access to green space, in low-economic standing, were most likely to manifest Hypocortisolemia, or low levels of cortisol throughout the day, which is usually an indicator for chronic stress.5 For this reason, it’s logical to conclude that poor women have the most to gain from increased green space in their neighborhoods.
The role accessible natural environments has on the development of children has been the subject of an increasing amount of research, related to fields like neurology, biological and cultural development, public health, education, and urban ecology. Much of the health status of adolescents and adults can be traced back to environmental stressors in an individual’s childhood. We know that factors like lead exposure, food insecurity, and hunger can affect behavioral disorders and cognitive abilities of low-income children. However, one study in Barcelona, Spain looked particularly at the impact “greenness” on a child’s environment can make a difference in their cognitive development.2
Cognitive health is described as conscious mental activities, such as learning, thinking, remembering, and understanding. The study in Barcelona utilized NDVI, a normalized difference vegetation index, to measure primary-school students’ exposure to green space- by combining areas near their homes, on their commutes to school, and at/in their schools. This index number was then compared to the measure of students’ tested progress in working memory, superior working memory, and inattentiveness. These abilities were chosen because they are constantly growing during preadolescence.2 The study demonstrated data that showed enhanced progress in memory and superior memory development, as well as a reduction in inattentiveness, over a 12-month period.2
Conclusively, we can project that regular interaction with the natural environment is an essential factor in the development of preadolescent cognitive abilities. Children and senior citizens are among the most vulnerable subpopulation groups, and the presented data identifies the importance of nature in childhood development, leading me to believe that green space may be one of the most effective practices in impacting overall public health.
Public Health is a division of medicine and public service that we usually associate with preventive care. This care takes the form of immunizations, sanitation, education, and regulations. But what if exposure to nature was considered preventative care? Women, men, and children all benefit by exposure to more green space and nature in their neighborhoods and commutes. Whether it be by decrease in chronic stress and other mental conditions, inattentiveness in students, or socioeconomic health inequalities, society and a city’s public health as a whole, benefits as well. Like most sustainable solutions, the installation of green space in cities provides an answer that addresses root causes of many public health obstacles. The city and greater governmental bodies have everything to gain from these projects- in funds that are now used to address curtailing poverty, educational support, health care costs, greater public safety enforcement, vandalism and property value, and gender empowerment.
It should be clarified that green space is not the ultimate solution to major issues facing public urban health, education, and poverty as an institution. However, it is a factor that offers significant systematic benefits to people and the planet.
Figures and Graphics
Figure 1: “Twelve month progress in superior working memory for participants with the first (low greenness) and third (high greenness) tertiles of greenness within the school boundaries”
Table 1: “Descriptive statistics summarized by quartiles for each of the six measurements of green space” 4
Figure 2: Incidence rate ratios for all-cause mortality in groups of exposure to green space, relative to group 1 (least exposure) 3
Figure 3: “Incidence rate ratios for all-cause mortality (A) and deaths from circulatory disease (B) in income-deprivation quartiles 2–4, relative to income deprivation quartile 1 (least deprived), stratified by exposure to green space” 3
Table 2: “Characteristics of the study population (n = 104)” 5
Table 3: “Relationships between cortisol patterns, health measures and percentage green space.” 5
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2.) Dadvand, Payam. “Green spaces and cognitive development in primary schoolchildren” Proceedings of the National Academy of Sciences of the United States of America. Volume 112. No. 26. (2015) Web. 5 October 2016
3.) Mitchell, Richard. “Effect of exposure to natural environment on health inequalities: an observational population study” The Lancet. Published Online (2008) Web. 5 October 2016
4.) Nutsford, D et. al. “An ecological study investigating the association between access to urban green space and mental health.” Public Health. Volume 127. Issue 11. (2013) Web. 5 October 2016
5.) Roe, Jenny J. et. al. “Green Space and Stress: Evidence from Cortisol Measures in Deprived Urban Communities” International Journal of Environmental Research and Public Health. Published Online (2013) Web. 5 October 2016
6.) Maas, J et. al. “Morbidity is related to a green living environment” Journal of Epidemiology & Community Health. Published Online (2009) Web. 15 November 2016.
7.) Rook, Graham A. “Regulation of the immune system by biodiversity from the natural environment: An ecosystem service essential to health” Proceedings of the National Academy of Sciences of the United States of America. Published by Yale University School of Medicine (2013). Web. 15 November 2016.
8.) Zhou, X. and Rana, M.M.P. “ Social benefits of urban green space: a conceptual framework of valuation and accessibility measurements.” Management of Environmental Quality International Journal. Published Online (2012) Web. 16 November 2016
9.) Boober, Becky H. “What Is Behavioral Health, Anyway?” Maine Health Access Foundation. Maine Health Access Foundation, 31 Aug. 2011. Web. 16 Nov. 2016.