Neighborhood blight, stress, and health: a walking trial of urban greening and ambulatory heart rate

Greenspace and Infant Mortality in Philadelphia, PA

Despite mounting evidence that urban greenspace protects against mortality in adults, few studies have explored the relationship between greenspace and death among infants. Here, we describe results from an analysis of associations between greenness and infant mortality in Philadelphia, PA. We used images of the normalized difference vegetation index (NDVI), derived from processed satellite data, to estimate greenness density in each census tract. We linked these data with census tract level counts of total infant mortality cases (n = 963) and births (n = 113,610) in years 2010-2014, and used Bayesian spatial areal unit, conditional autoregressive models to estimate associations between greenness and infant mortality. The models included a set of random effects to account for spatial autocorrelation between neighboring census tracts. Infant mortality counts were modeled using a Poisson distribution, and the logarithm of total births in each census tract was specified as the offset term. The following variables were included as potential confounders and effect modifiers: percentage non-Hispanic black, percentage living below the poverty line, an indicator of housing quality, and population density. In adjusted models, the rate of infant mortality was 27% higher in less green compared to more green tracts (95% CI 1.02-1.59). These results contribute further evidence that greenspace may be a health promoting environmental asset.

Might School Performance Grow on Trees? Examining the Link Between "Greenness" and Academic Achievement in Urban, High-Poverty Schools

In the United States, schools serving urban, low-income students are among the lowest-performing academically. Previous research in relatively well-off populations has linked vegetation in schoolyards and surrounding neighborhoods to better school performance even after controlling for important confounding factors, raising the tantalizing possibility that greening might boost academic achievement. This study extended previous cross-sectional research on the "greenness"-academic achievement link to a public school district in which nine out of ten children were eligible for free lunch. In generalized linear mixed models, Light Detection and Ranging (LiDAR)-based measurements of green cover for 318 Chicago public schools predicted statistically significantly better school performance on standardized tests of math, with marginally statistically significant results for reading-even after controlling for disadvantage, an index combining poverty and minority status. Pupil/teacher ratio %bilingual, school size, and %female could not account for the greenness-performance link. Interactions between greenness and Disadvantage suggest that the greenness-academic achievement link is different for student bodies with different levels of disadvantage. To determine what forms of green cover were most strongly tied to academic achievement, tree cover was examined separately from grass and shrub cover; only tree cover predicted school performance. Further analyses examined the unique contributions of "school tree cover" (tree cover for the schoolyard and a 25 m buffer) and "neighborhood tree cover" (tree cover for the remainder of a school's attendance catchment area). School greenness predicted math achievement when neighborhood greenness was controlled for, but neighborhood greenness did not significantly predict either reading or math achievement when school greenness was taken into account. Future research should assess whether greening schoolyards boost school performance.

Busy Streets Theory: The Effects of Community-engaged Greening on Violence

Lack of maintenance on vacant neighborhood lots is associated with higher levels of depression, anxiety, and stress for nearby residents. Overgrown grasses and dense brush provide hiding spots for criminals and space to conduct illicit activities. This study builds upon previous research by investigating greening programs that engage community members to conduct routine maintenance on vacant lots within their neighborhoods. The Clean & Green program is a community-based solution that facilitates resident-driven routine maintenance of vacant lots in a midsized, Midwestern city. We use mixed effects regression to compare assault and violent crime counts on streets where vacant lot(s) are maintained by community members (N = 216) versus streets where vacant lots were left alone (N = 446) over a 5-year timeframe (2009-2013). Street segments with vacant lots maintained through the Clean & Green program had nearly 40% fewer assaults and violent crimes than street segments with vacant, abandoned lots, which held across 4 years with a large sample and efforts to test counterfactual explanations. Community-engaged greening programs may not only provide a solution to vacant lot maintenance, but also work as a crime prevention or reduction strategy. Engaging the community to maintain vacant lots in their neighborhood reduces costs and may increase the sustainability of the program.

Effect of Greening Vacant Land on Mental Health of Community-Dwelling Adults: A Cluster Randomized Trial

IMPORTANCE

Neighborhood physical conditions have been associated with mental illness and may partially explain persistent socioeconomic disparities in the prevalence of poor mental health.

OBJECTIVE

To evaluate whether interventions to green vacant urban land can improve self-reported mental health.

DESIGN, SETTING, AND PARTICIPANTS

This citywide cluster randomized trial examined 442 community-dwelling sampled adults living in Philadelphia, Pennsylvania, within 110 vacant lot clusters randomly assigned to 3 study groups. Participants were followed up for 18 months preintervention and postintervention. This trial was conducted from October 1, 2011, to November 30, 2014. Data were analyzed from July 1, 2015, to April 16, 2017.

INTERVENTIONS

The greening intervention involved removing trash, grading the land, planting new grass and a small number of trees, installing a low wooden perimeter fence, and performing regular monthly maintenance. The trash cleanup intervention involved removal of trash, limited grass mowing where possible, and regular monthly maintenance. The control group received no intervention.

MAIN OUTCOMES AND MEASURES

Self-reported mental health measured by the Kessler-6 Psychological Distress Scale and the components of this scale.

RESULTS

A total of 110 clusters containing 541 vacant lots were enrolled in the trial and randomly allocated to the following 1 of 3 study groups: the greening intervention (37 clusters [33.6%]), the trash cleanup intervention (36 clusters [32.7%]), or no intervention (37 clusters [33.6%]). Of the 442 participants, the mean (SD) age was 44.6 (15.1) years, 264 (59.7%) were female, and 194 (43.9%) had a family income less than $25 000. A total of 342 participants (77.4%) had follow-up data and were included in the analysis. Of these, 117 (34.2%) received the greening intervention, 107 (31.3%) the trash cleanup intervention, and 118 (34.5%) no intervention. Intention-to-treat analysis of the greening intervention compared with no intervention demonstrated a significant decrease in participants who were feeling depressed (-41.5%; 95% CI, -63.6% to -5.9%; P = .03) and worthless (-50.9%; 95% CI, -74.7% to -4.7%; P = .04), as well as a nonsignificant reduction in overall self-reported poor mental health (-62.8%; 95% CI, -86.2% to 0.4%; P = .051). For participants living in neighborhoods below the poverty line, the greening intervention demonstrated a significant decrease in feeling depressed (-68.7%; 95% CI, -86.5% to -27.5%; P = .007). Intention-to-treat analysis of those living near the trash cleanup intervention compared with no intervention showed no significant changes in self-reported poor mental health.

CONCLUSIONS AND RELEVANCE

Among community-dwelling adults, self-reported feelings of depression and worthlessness were significantly decreased, and self-reported poor mental health was nonsignificantly reduced for those living near greened vacant land. The treatment of blighted physical environments, particularly in resource-limited urban settings, can be an important treatment for mental health problems alongside other patient-level treatments.

TRIAL REGISTRATION

isrctn.org Identifier: ISRCTN92582209.

The Power of Academic-Practitioner Collaboration to Enhance Science and Practice Integration: Injury and Violence Prevention Case Studies

One of the most substantial challenges facing the field of injury and violence prevention is bridging the gap between scientific knowledge and its real-world application to achieve population-level impact. Much synergy is gained when academic and practice communities collaborate; however, a number of barriers prevent better integration of science and practice. This article presents 3 examples of academic-practitioner collaborations, their approaches to working together to address injury and violence issues, and emerging indications of the impact on integrating research and practice. The examples fall along the spectrum of engagement with nonacademic partners as coinvestigators and knowledge producers. They also highlight the benefits of academic-community partnerships and the engaged scholarship model under which Centers for Disease Control and Prevention-funded Injury Control Research Centers operate to address the research-to-practice and practice-to-research gap.

Does spending time outdoors reduce stress? A review of real-time stress response to outdoor environments

Everyday environmental conditions impact human health. One mechanism underlying this relationship is the experience of stress. Through systematic review of published literature, we explore how stress has been measured in real-time non-laboratory studies of stress responses to deliberate exposure to outdoor environments. The types of exposures evaluated in this review include: nature viewing, outdoor walks, outdoor exercise and gardening. We characterize study design, modalities of stress measurements, and statistical estimates of effect and significance. Heart rate, blood pressure, and self-report measures provide the most convincing evidence that spending time in outdoor environments, particularly those with green space, may reduce the experience of stress, and ultimately improve health. More work is needed to understand effects of in situ modifications to outdoor environments on residents' stress response.

Urban Green Space and Its Impact on Human Health

Background: Over half of the world's population now lives in urban areas, and this proportion is expected to increase. While there have been numerous reviews of empirical studies on the link between nature and human health, very few have focused on the urban context, and most have examined almost exclusively cross-sectional research. This review is a first step toward assessing the possibility of causal relationships between nature and health in urban settings. Methods: Through systematic review of published literature, we explored the association between urban green space and human health. Results: We found consistent negative association between urban green space exposure and mortality, heart rate, and violence, and positive association with attention, mood, and physical activity. Results were mixed, or no association was found, in studies of urban green space exposure and general health, weight status, depression, and stress (via cortisol concentration). The number of studies was too low to generalize about birth outcomes, blood pressure, heart rate variability, cancer, diabetes, or respiratory symptoms. Conclusions: More studies using rigorous study design are needed to make generalizations, and meta-analyses, of these and other health outcomes possible. These findings may assist urban managers, organizations, and communities in their efforts to increase new or preserve existing green space.

Neighborhood Interventions to Reduce Violence

Violence is a widespread problem that affects the physical, mental, and social health of individuals and communities. Violence comes with an immense economic cost to its victims and society at large. Although violence interventions have traditionally targeted individuals, changes to the built environment in places where violence occurs show promise as practical, sustainable, and high-impact preventive measures. This review examines studies that use quasi-experimental or experimental designs to compare violence outcomes for treatment and control groups before and after a change is implemented in the built environment. The most consistent evidence exists in the realm of housing and blight remediation of buildings and land. Some evidence suggests that reducing alcohol availability, improving street connectivity, and providing green housing environments can reduce violent crimes. Finally, studies suggest that neither transit changes nor school openings affect community violence.

Urban Green Space and the Pursuit of Health Equity in Parts of the United States

Research has demonstrated that inequitable access to green space can relate to health disparities or inequalities. This commentary aims to shift the dialogue to initiatives that have integrated green spaces in projects that may promote health equity in the United States. Specifically, we connect this topic to factors such as community revitalization, affordable housing, neighborhood walkability, food security, job creation, and youth engagement. We provide a synopsis of locations and initiatives in different phases of development along with characteristics to support effectiveness and strategies to overcome challenges. The projects cover locations such as Atlanta (GA), Los Angeles (CA), the District of Columbia (Washington D.C.), South Bronx (NY), and Utica (NY). Such insight can develop our understanding of green space projects that support health equity and inform the dialogue on this topic in ways that advance research and advocacy.

Each meal matters in the exposome: Biological and community considerations in fast-food-socioeconomic associations

Advances in omics and microbiome technology have transformed the ways in which the biological consequences of life in the 'ecological theatre' can be visualized. Exposome science examines the total accumulated environmental exposures (both detrimental and beneficial) as a means to understand the response of the 'total organism to the total environment' over time. The repetitive stimulation of compensatory physiological responses (immune, cardiovascular, neuroendocrine) in response to stress - including sources of stress highly relevant to socioeconomic disadvantage - may lead to metabolic dysregulation and cellular damage, ultimately influencing behavior and disease. The collective toll of physiological wear and tear, known as allostatic load, is not paid equally throughout developed societies. It is paid in excess by the disadvantaged. In the context of fast-food, human and experimental research demonstrates that the biological response to a single fast-food-style meal - especially as mediated by the microbiome- is a product of the person's total lived experience, including the ability to buffer the fast-food meal-induced promotion of inflammation and oxidative stress. Emerging research indicates that each meal and its nutritional context matters. As we discuss, equal weekly visits to major fast-food outlets by the affluent and deprived do not translate into biological equivalency. Hence, debate concerning reducing fast-food outlets through policy - especially in disadvantaged neighborhoods where they are prevalent - requires a biological context. The fast-food establishment and fast-food meal - as they represent matters of food justice and press upon non-communicable disease risk - are far more than physical structures and collections of carbohydrate, fat, sugar and sodium.

The skin microbiome: impact of modern environments on skin ecology, barrier integrity, and systemic immune programming

Skin barrier structure and function is essential to human health. Hitherto unrecognized functions of epidermal keratinocytes show that the skin plays an important role in adapting whole-body physiology to changing environments, including the capacity to produce a wide variety of hormones, neurotransmitters and cytokine that can potentially influence whole-body states, and quite possibly, even emotions. Skin microbiota play an integral role in the maturation and homeostatic regulation of keratinocytes and host immune networks with systemic implications. As our primary interface with the external environment, the biodiversity of skin habitats is heavily influenced by the biodiversity of the ecosystems in which we reside. Thus, factors which alter the establishment and health of the skin microbiome have the potential to predispose to not only cutaneous disease, but also other inflammatory non-communicable diseases (NCDs). Indeed, disturbances of the stratum corneum have been noted in allergic diseases (eczema and food allergy), psoriasis, rosacea, acne vulgaris and with the skin aging process. The built environment, global biodiversity losses and declining nature relatedness are contributing to erosion of diversity at a micro-ecological level, including our own microbial habitats. This emphasises the importance of ecological perspectives in overcoming the factors that drive dysbiosis and the risk of inflammatory diseases across the life course.

The Association Between Urban Tree Cover and Gun Assault: A Case-Control and Case-Crossover Study

Green space and vegetation may play a protective role against urban violence. We investigated whether being near urban tree cover during outdoor activities was related to being assaulted with a gun. We conducted geographic information systems-assisted interviews with boys and men aged 10-24 years in Philadelphia, Pennsylvania, including 135 patients who had been shot with a firearm and 274 community controls, during 2008-2011. Each subject reported a step-by-step mapped account of where and with whom they traveled over a full day from waking until being assaulted or going to bed. Geocoded path points were overlaid on mapped layers representing tree locations and place-specific characteristics. Conditional logistic regressions were used to compare case subjects versus controls (case-control) and case subjects at the time of injury versus times earlier that day (case-crossover). When comparing cases at the time of assault to controls matched at the same time of day, being under tree cover was inversely associated with gunshot assault (odds ratio (OR) = 0.70, 95% confidence interval (CI): 0.55, 0.88), especially in low-income areas (OR = 0.69, 95% CI: 0.54, 0.87). Case-crossover models confirmed this inverse association overall (OR = 0.55, 95% CI: 0.34, 0.89) and in low-income areas (OR = 0.54, 95% CI: 0.33, 0.88). Urban greening and tree cover may hold promise as proactive strategies to decrease urban violence.

Landscape care of urban vacant properties and implications for health and safety: Lessons from photovoice

Care of vacant properties in urban environments is of particular interest to planners and residents alike. We report on a photovoice project completed by community leaders, researchers, and residents in two Detroit neighborhoods experiencing longtime systemic disinvestment. Participants photographed and discussed examples of care in a series of three focus groups in each neighborhood. Analyses highlight how acts of landscape care and visible cues to care contribute to changes in physical and social environments, and explore various links to health. We suggest theoretical and practical applications of residents' perspectives on landscape care and identify implications for well-being and neighborhood stability.

Information requirements to create public value: sharing and opening data to address urban blight

Purpose

Blighted and vacant properties represent a persistent and costly problem for cities and local governments throughout the USA. The purpose of this paper is to identify data needs and requirements for value creation in the context of urban blight. The main assumption is that sharing and opening data through a robust and effective code enforcement program will facilitate more informed management, mitigation and remediation of blighted and vacant properties. Code enforcement programs must be grounded on organizational and technical infrastructures that enable data sharing and value creation for the city and the communities that share its space.

Design/methodology/approach

In this paper, the information needs and realities of a city’s code enforcement environment are described, based on data gathered through a series of workshops and focus groups with a range of stakeholders, which included city government departments, police, fire, bank representatives, realtors and community groups.

Findings

The analysis reveals key data elements that could potentially help to build a code enforcement program to better manage the cycles and costs of urban blight. Although some of these data elements already exist, and are public, they are not easily accessible to key stakeholders. The paper ends with sets of short-term and long-term recommendations for establishing an information-sharing infrastructure, which would serve as the main conduit for exchanging code enforcement data among a number of city government departments and the public that may play a role in managing urban blight and its consequences.

Originality/value

In this paper, the authors are connecting extant literature on sharing and opening data with literature on the creation of public value. They argue that sharing and opening government data constitute effective ways of managing the costs and cycles of urban blight while creating value. As a result of an initial assessment of data and information requirements, the authors also point to specific data and its potential value from stakeholder perspective.

Transforming Life: A Broad View of the Developmental Origins of Health and Disease Concept from an Ecological Justice Perspective

The influential scientist Rene J. Dubos (1901–1982) conducted groundbreaking studies concerning early-life environmental exposures (e.g., diet, social interactions, commensal microbiota, housing conditions) and adult disease. However, Dubos looked beyond the scientific focus on disease, arguing that “mere survival is not enough”. He defined mental health as fulfilling human potential, and expressed concerns about urbanization occurring in tandem with disappearing access to natural environments (and elements found within them); thus modernity could interfere with health via “missing exposures”. With the advantage of emerging research involving green space, the microbiome, biodiversity and positive psychology, we discuss ecological justice in the dysbiosphere and the forces—financial inequity, voids in public policy, marketing and otherwise—that interfere with the fundamental rights of children to thrive in a healthy urban ecosystem and learn respect for the natural environment. We emphasize health within the developmental origins of health and disease (DOHaD) rubric and suggest that greater focus on positive exposures might uncover mechanisms of resiliency that contribute to maximizing human potential. We will entrain our perspective to socioeconomic disadvantage in developed nations and what we have described as “grey space”; this is a mental as much as a physical environment, a space that serves to insidiously reinforce unhealthy behavior, compromise positive psychological outlook and, ultimately, trans-generational health. It is a dwelling place that cannot be fixed with encephalobiotics or the drug-class known as psychobiotics.

Urban Blight Remediation as a Cost-Beneficial Solution to Firearm Violence

OBJECTIVES

To determine if blight remediation of abandoned buildings and vacant lots can be a cost-beneficial solution to firearm violence in US cities.

METHODS

We performed quasi-experimental analyses of the impacts and economic returns on investment of urban blight remediation programs involving 5112 abandoned buildings and vacant lots on the occurrence of firearm and nonfirearm violence in Philadelphia, Pennsylvania, from 1999 to 2013. We adjusted before-after percent changes and returns on investment in treated versus control groups for sociodemographic factors.

RESULTS

Abandoned building remediation significantly reduced firearm violence -39% (95% confidence interval [CI] = -28%, -50%; P < .05) as did vacant lot remediation (-4.6%; 95% CI = -4.2%, -5.0%; P < .001). Neither program significantly affected nonfirearm violence. Respectively, taxpayer and societal returns on investment for the prevention of firearm violence were $5 and $79 for every dollar spent on abandoned building remediation and $26 and $333 for every dollar spent on vacant lot remediation.

CONCLUSIONS

Abandoned buildings and vacant lots are blighted structures seen daily by urban residents that may create physical opportunities for violence by sheltering illegal activity and illegal firearms. Urban blight remediation programs can be cost-beneficial strategies that significantly and sustainably reduce firearm violence.

Receiving Support, Giving Support, Neighborhood Conditions, and Waist/Hip Ratios

Obesity is a major health problem in the USA, and as a result, it is important to identify the factors that help people keep their body weight within healthy limits. The purpose of this study was to see whether receiving support at church and giving support at church buffer (i.e., moderate) the effects of living in rundown neighborhoods on a key marker of obesity-waist/hip ratios (WHR). The data are provided from a recent nationwide survey of people age 18 and older (N = 1456). The findings reveal that giving support to fellow church members tends to offset the effects of living in dilapidated neighborhoods on WHR. In contrast, receiving support from coreligionists does not appear to perform a similar stress-moderating function. The theoretical underpinnings of providing support at church are discussed.

Modifiable Neighborhood Features Associated With Adolescent Homicide

IMPORTANCE

Homicide is a leading cause of adolescent mortality. To our knowledge, relatively little has been studied in terms of the association between environmental neighborhood features, such as streets, buildings, and natural surroundings, and severe violent injury among youth.

OBJECTIVE

To assess associations between environmental neighborhood features and adolescent homicide in order to identify targets for future place-based interventions.

DESIGN, SETTING, AND PARTICIPANTS

Population-based case-control study conducted in Philadelphia, Pennsylvania, from April 15, 2008, to March 31, 2014. We identified adolescents who died by homicide at 13 to 20 years of age from 2010 to 2012 while residing in Philadelphia. We used incidence-density sampling and random-digit dialing to recruit control participants ages 13 to 20 years matched on sex and indoor-outdoor location at the time of each index case participant's homicide.

EXPOSURES

To obtain environmental data about modifiable features that were present in the immediate surroundings of our case and control participants, blinded field researchers used standardized techniques to photograph case and control participant outdoor locations. Photographic data were stitched together to create 360° panoramic images that were coded for 60 elements of the visible environment.

MAIN OUTCOME AND MEASURE

Adolescent homicide.

RESULTS

We enrolled 143 homicide case participants (mean [SD] age, 18.4 [1.5] years) and 155 matched control participants (mean [SD] age, 17.2 [2.1] years) who were both outdoors at the time of the homicide. In adjusted analyses, multiple features of Philadelphia streets, buildings, and natural surroundings were associated with adolescent homicide. The presence of street lighting (odds ratio [OR], 0.24; 95% CI, 0.09-0.70), illuminated walk/don't walk signs (OR, 0.16; 95% CI, 0.03-0.92), painted marked crosswalks (OR, 0.17; 95% CI, 0.04-0.63), public transportation (OR, 0.13; 95% CI, 0.03-0.49), parks (OR, 0.09; 95% CI, 0.01-0.88), and maintained vacant lots (OR, 0.17; 95% CI, 0.03-0.81) were significantly associated with decreased odds of homicide. The odds of homicide were significantly higher in locations with stop signs (OR, 4.34; 95% CI, 1.40-13.45), security bars/gratings on houses (OR, 9.23; 95% CI, 2.45-34.80), and private bushes/plantings (OR, 3.44; 95% CI, 1.18-10.01).

CONCLUSIONS AND RELEVANCE

Using a population-based case-control design, we identified multiple modifiable environmental features that might be targeted in future randomized intervention trials designed to reduce youth violence by improving neighborhood context.

Restoration in Its Natural Context: How Ecological Momentary Assessment Can Advance Restoration Research

More and more people use self-tracking technologies to track their psychological states, physiology, and behaviors to gain a better understanding of themselves or to achieve a certain goal. Ecological Momentary Assessment (EMA) also offers an excellent opportunity for restorative environments research, which examines how our physical environment (especially nature) can positively influence health and wellbeing. It enables investigating restorative health effects in everyday life, providing not only high ecological validity but also opportunities to study in more detail the dynamic processes playing out over time on recovery, thereby bridging the gap between laboratory (i.e., short-term effects) and epidemiological (long-term effects) research. We have identified four main areas in which self-tracking could help advance restoration research: (1) capturing a rich set of environment types and restorative characteristics; (2) distinguishing intra-individual from inter-individual effects; (3) bridging the gap between laboratory and epidemiological research; and (4) advancing theoretical insights by measuring a more broad range of effects in everyday life. This paper briefly introduces restorative environments research, then reviews the state of the art of self-tracking technologies and methodologies, discusses how these can be implemented to advance restoration research, and presents some examples of pioneering work in this area.

Cumulative Environmental Impacts: Science and Policy to Protect Communities

Many communities are located near multiple sources of pollution, including current and former industrial sites, major roadways, and agricultural operations. Populations in such locations are predominantly low-income, with a large percentage of minorities and non-English speakers. These communities face challenges that can affect the health of their residents, including limited access to health care, a shortage of grocery stores, poor housing quality, and a lack of parks and open spaces. Environmental exposures may interact with social stressors, thereby worsening health outcomes. Age, genetic characteristics, and preexisting health conditions increase the risk of adverse health effects from exposure to pollutants. There are existing approaches for characterizing cumulative exposures, cumulative risks, and cumulative health impacts. Although such approaches have merit, they also have significant constraints. New developments in exposure monitoring, mapping, toxicology, and epidemiology, especially when informed by community participation, have the potential to advance the science on cumulative impacts and to improve decision making.

Nature-Based Strategies for Improving Urban Health and Safety

Place-based programs are being noticed as key opportunities to prevent disease and promote public health and safety for populations at-large. As one key type of place-based intervention, nature-based and green space strategies can play an especially large role in improving health and safety for dwellers in urban environments such as US legacy cities that lack nature and greenery. In this paper, we describe the current understanding of place-based influences on public health and safety. We focus on nonchemical environmental factors, many of which are related to urban abandonment and blight. We then review findings from studies of nature-based interventions regarding impacts on health, perceptions of safety, and crime. Based on our findings, we suggest that further research in this area will require (1) refined measures of green space, nature, and health and safety for cities, (2) interdisciplinary science and cross-sector policy collaboration, (3) observational studies as well as randomized controlled experiments and natural experiments using appropriate spatial counterfactuals and mixed methods, and (4) return-on-investment calculations of potential economic, social, and health costs and benefits of urban greening initiatives.