Abstract
Climate change has amplified the effects of extreme heat events (EHEs), exacerbating heat-related morbidity and mortality, particularly in cities due to the urban heat island effect. While a long-term solution to mitigating heat exists via urban greening, less is known about how to implement an urban greening plan co-designed by community members that addresses heat-related health outcomes. To examine the current state of urban greening interventions focused on communities and heat mitigation, we conducted a scoping review of papers at the nexus of urban greening/forestry, heat-related health outcomes, and community engagement. We then evaluated 46 eligible papers using a conceptual framework informed by the literature with the following criteria: (1) identification of urban green space/trees for climate change-amplified heat mitigation with quantifiable benefits; (2) association between objective heat-related health outcomes/health equity and urban greening intervention design; and (3) sustainable and ongoing community engagement and/or community co-creation. We found multiple differences between study methods. Most papers lacked objective heat-related health outcomes data and instead focused on subjective thermal comfort/heat stress measures. Additionally, almost all papers utilized one-time community engagement methods such as surveys or interviews to inform urban greening recommendations or study findings. Our findings have useful implications for urban greening decision-making, further emphasizing the importance of transdisciplinary cooperation and long-term community engagement, so an equitable, context-dependent urban greening and health intervention can be effectively co-produced by city planners, public health officials, and community members.
Introduction
Climate change is resulting in an increasingly warmer and more variable climate (Watts et al. 2015), promoting the frequency and severity of extreme heat events (EHEs)(Meehl and Tebaldi 2004; Habeeb et al. 2015). EHEs, including heat waves, have become the most deadly extreme weather event; in the United States alone, there were an average of 702 heat-related deaths each year from 2004 to 2018 (Vaidyanathan et al. 2020; National Weather Service [date unknown]). Exposure to extreme heat can also cause widespread heat-related illness and worsen other health conditions, such as respiratory conditions, sleep disorders, cardiovascular disease, digestive illness, psychological distress, and risk of preterm birth (Gasparrini et al. 2017; Sun et al. 2019; Chersich et al. 2020; Marí-Dell’Olmo et al. 2022).
Excess heat is a particularly pronounced issue in cities, where the majority of the global population now lives (World Bank Group 2022). In urban areas, heat is exacerbated by the urban heat island (UHI) effect, wherein higher air and surface temperatures regularly develop in contrast to surrounding rural areas. UHIs are formed through a combination of a lack of vegetation cover, greater heat storage from solar radiation within urban materials, and a wide range of sources of anthropogenic heat (e.g., combustion engines; heating, ventilation, and air conditioning systems; and human metabolism)(Oke 1982; Taha 1997; Zhao et al. 2014). Efforts to reduce heat-related health issues in urban environments are primarily focused on short-term adaptative solutions (e.g., air conditioning, access to cooling centers, or heat advisory messaging) rather than long-term planning (Vaidyanathan et al. 2019; Patel et al. 2022). Short-term solutions such as air conditioning face challenges such as high energy costs for low-income residents (Lundgren-Kownacki et al. 2018) and collapse of energy infrastructure; therefore, if a black out occurs and limits air conditioning availability during times of high demand, or if a household cannot afford to turn on air conditioning, the threat of extreme heat exposure will be greatly increased (Stone et al. 2021). A recent study found that heat wave and grid failure events can expose between 68% to 100% of urban residents to an elevated risk of heat-related illness (Stone et al. 2021).
Social-ecological systems research focuses on the complex interactions between humans and nature; for example, this research may assess a system’s adaptive capacity and available resources to respond to climate change consequences such as extreme heat (Ostrom 2009; Pant et al. 2015). A proven long-term solution to mitigating the effects of urban heat through natural resources is the expansion of quality urban green space (Hu and Li 2020; Wong et al. 2021; Zhao et al. 2021), which encompasses all vegetation in cities (e.g., parks, street trees, greenways, stormwater beds, vegetation on private land, and community gardens). Solutions that use nature to address complex socio-ecological challenges, such as climate change mitigation/adaptation and human health, are termed nature-based solutions (Dunlop et al. 2024). For example, maintaining and expanding urban forest cover is a nature-based solution to mitigate climate change effects in cities and is of burgeoning interest to urban planners due to the myriad benefits provided by trees, including cooling through shading and evapotranspiration (i.e., latent heat loss through water vaporization through plant stomata and on surfaces)(Eisenman et al. 2021). Other urban greening interventions besides tree planting include the installation of “green roofs”, “green corridors”, and community gardens— all of which would also be a form of nature-based solutions. During EHEs, the surface temperature of shaded areas may be up to 20 °C cooler than unshaded areas, and evapotranspiration alone can reduce air temperatures by 1° to 8 °C (Winbourne et al. 2020). Beyond cooling benefits, trees and urban green space provide an abundance of other ecosystem services, including stormwater management, soil stabilization, cultural and aesthetic benefits, mental health improvement, and air pollution mitigation (Salmond et al. 2016; Berland et al. 2017; Woodward et al. 2023).
Despite these known benefits, green space in cities is inequitably distributed across neighborhoods; in other words, some communities face environmental injustice through the unequal distribution of environmental burdens (McPhearson et al. 2013; McDonald et al. 2021). Communities facing environmental injustice with limited access to quality green space often have a higher proportion of marginalized individuals, including people of color and the socio-economically disadvantaged (Schwarz et al. 2015; Nyelele and Kroll 2020; Forest for All NYC 2021). Tackling complex issues such as climate change-related health inequity requires a social ecological approach (Golden and Earp 2012). An individual’s socio-economic status, sociopolitical identities, access to quality healthcare and education, and the surrounding built and natural environment are examples of social determinants of health—all factors that influence an individual’s health status (US Department of Health and Human Services [date unknown]; Chelak and Chakole 2023). Together with spatial inequities in urban green space, the social determinants of health may multiply the risks of extreme heat events and heat-related illness in already vulnerable communities (Schmeltz et al. 2015; Schell et al. 2020; Vaidyanathan et al. 2020; Jung et al. 2021).
In recent years, city agencies have become increasingly cognizant of and have taken steps to reduce these inequities to improve environmental justice. For example, in New York City (NYC), the NYC Parks Department hosts tree care volunteer events in neighborhoods with high heat vulnerability to encourage expanding tree canopy cover and the ensuing cooling benefits (New York City Department of Parks & Recreation [date unknown]). Furthermore, other studies have recognized the importance of incorporating community participation in green space design; Oosterbroek et al. (2024) implemented a framework for active participatory green space design that incorporates community preferences and health data (Oosterbroek et al. 2024). Nevertheless, urban greening interventions are often implemented without input from communities, which can result in vegetation planted in unwelcome locations (Barbuti 2023) and can result in unintended consequences such as green gentrification (Anguelovski et al. 2022). Urban greening may also introduce other disservices to the community, including safety concerns, inadvertent health consequences (e.g., allergenic pollen), and physical damage to property (Lyytimäki et al. 2008; Conway and Yip 2016). Therefore, as cities choose to expand and improve upon urban green space with good intentions for the long-term health of the community, it has become increasingly necessary to engage communities in green space trade-off assessments and decision making (Roman et al. 2021).
As heat-related deaths and hospitalizations rise (Vaidyanathan et al. 2024), the direct connections made between urban greening programs and heat-related public health policies and tools grow in importance: a link that is needed for climate and health policy makers. For example, the US National Integrated Heat Health Information System (NIHHIS) and the White House developed a National Heat Strategy to “build societal understanding of heat risks, develop science-based solutions, [and] improve capacity, communication, and decision-making to reduce heat-related illness and death” (National Integrated Heat Health Information System 2024b). This strategy recognizes the importance of green space, green infrastructure, and nature-based solutions as vital components of heat-related health and resilience (National Integrated Heat Health Information System 2024a). Public health initiatives such as this one urgently require studies that assess urban greening and heat-related health to build evidence-based, long-term solutions to protect those most vulnerable to the effects of rising temperatures.
Therefore, we undertook a literature review at the nexus of urban greening, heat-related health outcomes, and community engagement to explore the state of the current research across disciplines and to evaluate the strengths of the literature that will most effectively guide evidence-based research and planning of urban greening programs and therefore improve heat-related health and health equity.
Methods
Scoping Review
For our literature review, we conducted a scoping review, which has recently been defined as “a type of evidence synthesis that aims to systematically identify and map the breadth of evidence available on a particular topic”, and can assist with identifying key concepts or themes within the literature (Munn et al. 2022). To do so, we systematically examined the literature across multiple databases and employed the inclusion and exclusion criteria to derive a final list of relevant manuscripts. We developed our inclusion and exclusion criteria through consensus. Our inclusion criteria were manuscripts that focused on all 3 of the following: (1) Urban Forestry, Urban Greening, or Urban Green Infrastructure; (2) Heat-related health outcomes; and (3) Community perception or community engagement. Papers met the first requirement if they mentioned any form of urban greening or urban green infrastructure (e.g., tree planting) in the context of heat mitigation. Papers met the second requirement if they explicitly connected heat with health outcomes data (e.g., mortality rates, hospitalization rates, self-reported health data). This criterion was based on the definition of health outcomes, which can be measured clinically, self-reported, or observed, and are health events occurring at the “result of an intervention”; in this study, this is the health event due to heat (Oleske and Islam 2019). Papers met the third requirement if they utilized direct community engagement through qualitative or quantitative research methods (e.g., questionnaire surveys or focus groups) with a defined community (e.g., geographic, identity) that focused on community perceptions. Excluded studies were: (1) non-English language studies; (2) nonhuman population studies; or (3) studies that only assessed rural communities. The search was completed on 2024 October 21 in PubMed, Web of Science (Core Collection; Clarivate, Philadelphia, PA, USA), and Scopus (Elsevier, Amsterdam, Netherlands) and included appropriate controlled vocabulary and keywords for the concepts of “greening”, “community”, and “heat-related health”. The full search strategy can be found in the supplementary materials section (Supplementary File 1).
After deduplication, we screened 2,505 studies for inclusion using Covidence systematic review software (Veritas Health Innovation, Melbourne, VIC, Australia), a software that is agnostic to discipline and has been used in a variety of disciplines including the health sciences. First, we screened titles/abstracts, and then we screened full-text papers against the inclusion/exclusion criteria. Eligibility was determined by at least 2 screeners independently per paper, and conflicts were resolved through consensus meetings. The PRISMA diagram outlining the process described above is presented in Figure 1 and was created using the Covidence PRISMA tool.
PRISMA diagram of review process.
Data Extraction and Evaluation
We then extracted and summarized the following information from each included study: Author/Year and Title, Location, Köppen Climate Classification, Definition of Community Engaged, Method of Community Engagement, Urban Greening Description or Definition, Heat-Related Health Outcome, and Summary of Findings (Table 1). All figures and tables for data extraction were created with Microsoft Excel (Microsoft, Redmond, WA, USA). Subsequently, we evaluated how each study aligned with a framework adapted from the conceptual tree-planting framework devised by Hopkins et al. (2022). This framework allowed us to categorize the papers that address the intersection of heat-related health, urban greening interventions, and community engagement using a “multisectoral, collaborative, and environmental data driven approach” (Hopkins et al. 2022). We adapted this framework for evaluating the scope of the literature because of the acceleration of climate change-amplified extreme heat events and because of the growing need for evidence-based research that is particularly useful for climate and health decisionmakers and policy (National Integrated Heat Health Information System 2024a).
Description of papers. PEH (persons experiencing homelessness); LST (land surface temperature); PET (physiological equivalent temperature); mPET (modified physiological equivalent temperature); COMFA (COMfort ForumlA); SDU (subdivided units); GS (green space); UGS (urban green space); UHI (urban heat island); UHIR (urban heat island reduction); PP (pocket parks); IP (interim plazas); POP (privately owned public spaces); GIS (geographic information system).
Rationale for Adapted Evaluation Criteria
The evaluation criteria of eligible papers were as follows: Criteria #1. Identification of urban greening/ forestry/other nature-based solutions for climate change-amplified heat mitigation with quantifiable benefits; Criteria #2. Association between objective heat-related health outcomes/health equity and urban greening interventions; and Criteria #3. Sustainable and ongoing community engagement and/or community co-creation.
Criteria #1, the quantification of urban greening benefits, is well-studied, particularly in the context of ecosystem services, which are the benefits humans receive from ecosystems, and are often classified as either provisioning, regulating, supporting, or cultural services (Millennium Ecosystem Assessment 2005). Understanding ecosystem services in urban planning research helps to explain how humans benefit from the natural environment in the complex socio-ecological system of a city, as well as to estimate the economic value of the benefits (de Groot et al. 2012; Kremer et al. 2015). Estimates of ecosystem services inform local, state, and federal plans and policies that utilize the natural ecosystem for public health benefits and climate change resilience (Kremer et al. 2015; Kapoor et al. 2020). Papers fit Criteria #1 if the study found quantifiable climate-amplified heat mitigation benefits from urban greening, such as through biometeorological/microclimate measurements, spatial modelling, or subjective experiences.
Criteria #2, the association between objective heat-related health outcomes/health equity and urban greening, further emphasizes the importance of quantifying benefits from urban greening, but from a public health perspective. A plethora of studies have found strong evidence for green space benefits on public health outcomes, both physical and mental (Kruize et al. 2019). That said, fewer studies have measured objective health outcomes from urban greening, despite the importance of health metrics to urban greening design and implementation (Zhang et al. 2021) and the persistence of health inequities in communities facing environmental injustice (Hopkins et al. 2022). As extreme heat events increase, it will become particularly important that objective heat-related health outcomes data is included as well to strengthen public health data access for policymakers (US Centers for Disease Control and Prevention 2024). Papers therefore fit Criteria #2 if the study utilized objective heat-related health outcomes/health equity data to inform urban greening research and planning.
Finally, Criteria #3, sustainable and ongoing community engagement and/or community co-creation, was our final criterion and another topic that has been well-established in the environmental justice literature, which emphasizes the importance of meaningful community involvement in nature-based solutions. Historical systemic injustices often shape current patterns of heat-related health inequity and environmental injustice, and interventions that lack community engagement heighten the probability of perpetuating inequities (i.e., green gentrification)(Amorim-Maia et al. 2022). This criterion also emphasizes the importance of understanding axes of vulnerability and establishing community buy-in to redistribute power and benefits to those facing environmental injustice (i.e., procedural justice). Co-production of green space not only improves the chances of planting success and increased health benefits but also fosters strong community ties and social cohesion (Bhandari 2023). Therefore, environmental justice-focused research and interventions require further interaction with communities beyond surveys and the maintenance of long-lasting and collaborative relationships with communities (Amorim-Maia et al. 2022). Papers met Criteria #3 if they had evidence of more than one touchpoint with communities (e.g., through meetings), and incorporated elements such as co-creation, education, or engagement events in their study design.
Results
Characteristics of Included Papers
In Table 1 we summarized 46 studies which met the criteria for inclusion in the analysis. Of the studies, half were from Asia (23/46: Malaysia, China, Singapore, India, Pakistan, Saudi Arabia, and Thailand), and most of the remaining half were from North America (10/46: United States and Mexico) and Europe (11/46: Germany, Cyprus, The Netherlands, Spain, Austria, United Kingdom, and Italy), with one each from South America (Brazil) and Australia (Melbourne) and none from Africa. The majority of the studies (34/46) were conducted in temperate climates (“C” Köppen climate classification: Csa, Csb, Cfa, Cwa, Cfb), with the next most common climate (9/46) being dry (arid)(“B” Köppen climate classification: BWh, BSk, BSh), and then tropical (4/46)(“A” Köppen climate classification: Af, Aw), and finally continental (2/46)(“D” Köppen climate classification: Dwa). The counts for climate classification add up to more than 46 due to the occurrence of more than one climate classification in some studies, either due to multiple study sites (Lafortezza et al. 2009) or due to 2 known classifications in one location (Giannakis et al. 2016). Results can be found in Figure 2 and Figure 3.
Geographic distribution of papers.
Köppen climate classification distribution.
The majority of studies utilized surveys as the means of community engagement methods (i.e., online, in-person, mail-back, telephone) or semistructured interview only (41/46). The other 5 had some form of community co-creation or further engagement (e.g., participatory planning, ecological stewardship events, educational workshops). One of the studies used physiological measurements along with surveys (Rathmann et al. 2020). Results can be found in Table 2.
Community engagement methods.
When discussing urban greening, over 80% of studies used the phrase “urban green space”, “urban green area”, or “urban greening” (38/46) and/or “urban forest” or “trees” (40/46). Nearly a third of studies (15/46) described “green infrastructure” and/ or described greenspace as “vegetation” (14/46). About 22% described urban greening as an “intervention” (10/46)(e.g., “urban heat intervention”, “greening intervention”, “tactical urbanism intervention”, “tree planting intervention”, “climate intervention”, “mitigation/ adaptation intervention”, etc.). Finally, only 17% (8/46) described “nature/natural-based solutions”. Results can be found in Table 3.
Urban greening terms.
Lastly, for heat-related health outcomes, the over-whelming majority of papers used self-reported measures of heat stress, thermal comfort, or heat-related illness (43/46). Only 5 papers reported some objective measure of heat-related health (e.g., morbidity and mortality rates, physiological measurements, hospitalization/ambulance records). Two papers included both subjective and objective measures (Guardaro et al. 2020; Rathmann et al. 2020). Results can be found in Table 4.
Heat-related health outcomes.
Conceptual Framework Evaluation
According to our adapted framework, 40 papers met Criteria #1: Identification of urban greening/forestry/ other nature-based solution for climate change-amplified heat mitigation with quantifiable benefits; 5 met Criteria #2: Association between objective heat-related health outcomes/health equity and urban greening interventions; and 5 met Criteria #3: Sustainable and ongoing community engagement and/or community co-creation. Two papers met all three criteria: Hopkins et al. (2022), the paper that our criteria were modelled after; and Nahban et al. (2020). Both papers identified a type of urban greening intervention to mitigate climate-amplified heat in urban areas; presented objective heat-related health outcomes specific to that region; and performed meaningful community engagement. In Hopkins et al. (2022), this was accomplished through a tree planting framework that was developed by expert stakeholders to identify and rank a list of native tree species based on their physiology and climate-related ecosystem services. Then, locations to plant the trees with the best climate-mitigation rankings were chosen based on maps depicting high rates of cardiac arrest and asthma attacks. The previously mentioned steps engaged multiple stakeholders within each step, but after trees and locations were chosen, additional partners were engaged across many other sectors through meetings, lectures, webinars, and on-site tree demonstrations (Hopkins et al. 2022). In Nabhan et al. (2020), the authors identified the consistent positive benefits received from a youth ecological restoration program, including sense of community and improved emotional and physical strength. Then, they identified the importance of restoration engagement efforts to mitigate rising rates of coccidiomycosis (valley fever) in the desert Southwest in the United States, a heat-exacerbated disease that can be reduced with habitat restoration in desert environments. Finally, they emphasized the importance of ecological restoration programs as ways to engage youth in not only scientific research and discovery but also in the restoration of their own health and well-being as well as the health of their environment (Nabhan et al. 2020).
The papers that met Criteria #1 explicitly quantified urban greening benefits in the context of heat mitigation through either objective or subjective measures (and often with both). The mechanisms for assessing urban greening benefits fell within categories established by Zhang et al. (2021): (1) heat mitigation benefits provided by urban green space; (2) heat-related physiological and psychological effects; and (3) healthy behaviors (i.e., climate mitigation and adaptation strategies) motivated by green space. For example, Maghrabi et al. (2021) assessed resident perceptions of the role of green space through surveys and found that 85% of the respondents saw green space as playing a “crucial” role in temperature regulation and urban heat island effect reduction (Maghrabi et al. 2021). Similarly, Sousa-Silva and Zanocco (2024) evaluated residents’ perceived benefits of green space as well as heat adaptation behaviors associated with green space, finding that despite positive attitudes towards green space, fewer than 20% of the respondents visited green spaces on hot days (Sousa-Silva and Zanocco 2024). By contrast, Rosso et al. (2024) used microclimate measurements to determine that air temperature was marginally cooler in urban pocket parks in New York City, NY, USA, compared to the surrounding streets, and different park types had varying levels of cooling efficiency (Rosso et al. 2024).
The papers that met Criteria #2 used objective heat-related health outcomes to inform urban greening designs or recommendations. For example, Huanchun et al. (2021) created a simulation of potential green space designs based on reducing the urban heat island effects on respiratory disease, cardiovascular disease, and emotional health. In another example, but with different methods, Rathmann et al. (2020) explored the positive effects of urban greening on heat-related well-being through human physiological measures (e.g., blood pressure readings) and found that urban greening did have positive effects on human physiological measures (e.g., reduction in heart rate). Other studies utilized hospitalization or ambulance records to explain heat-related health outcomes and inform green space design (Kilbourne et al. 1982; Hopkins et al. 2022).
The papers that met Criteria #3 varied in their goals, which may be due to the plethora of ways that community engagement can occur. For example, Nabhan et al. (2020) focused on ecological restoration programs as a way to engage at-risk youth with nature-based interventions to improve both human and ecosystem health during extreme heat. Oosterbroek et al. (2024), on the other hand, provided an example of participatory green space design with elderly and youth residents through multiple design meetings and iterations. Other studies emphasized multistakeholder engagement meetings and educational community workshops (Guardaro et al. 2020; Ehsan et al. 2021; Hopkins et al. 2022).
Results and examples from papers can be found in Table 5.
Evaluation of eligible papers. UHIR (urban heat island reduction); PP (pocket parks); IP (interim plazas); POPs (privately owned public spaces); GIS (geographic information systems).
Discussion
Our scoping review found 46 eligible papers at the nexus of urban greening, heat-related health outcomes, and community engagement. To further assess the gaps in the literature and potential areas of future research, we evaluated the 46 eligible papers using a framework adapted from a tree planting framework created by Hopkins et al. (2022). Our adapted framework recognized studies that identified quantifiable heat mitigation benefits of urban green/forestry/other nature-based solutions, associated urban greening interventions with objective heat-related health outcomes, and/or engaged meaningfully with communities of interest. Through this evaluation, we found that there were key differences in research context, methods, and empirical questions between studies.
For example, most of the studies we assessed were focused on urban climatology and biometeorology methods to inform urban planning. This included studies that quantified subjective and objective thermal data (e.g., thermal comfort, heat stress, physiological equivalent temperature) in urban areas but were not as focused on providing quantifiable heat-related health/thermal comfort benefits of urban greening (Li et al. 2023). Papers that did measure quantifiable urban greening benefits often assessed self-reported health outcomes or healthy behaviors due to green space and did not consider objective heat-related health outcomes (e.g., mortality rates, hospitalization admissions)(Maghrabi et al. 2021). Finally, few of the studies engaged with communities repeatedly and meaningfully, primarily utilizing one-time surveys and interviews, a finding that is similar to other studies that evaluate equity in green infrastructure planning (Grabowski et al. 2023).
This is the first review of our knowledge to evaluate the literature at this intersection and highlights several opportunities to bring together 3 core ideas of growing interest nationally and internationally—the use of nature-based solutions to protect against the health effects of extreme heat, particularly among vulnerable communities. For example, in the United States, the previously mentioned National Heat Strategy calls for quantifiable public health and urban forestry benefits, particularly to add sophistication to economic valuation of urban greening (National Integrated Heat Health Information System 2024a).
Future research can therefore benefit from comparing biometeorological and subjective thermal data with objective heat-related health outcomes (e.g., heat-related mortality rates or hospitalization admissions) to further inform green space design and placement, particularly because this type of health outcomes data is useful for public health policy and interventions (US Centers for Disease Control and Prevention 2024). Furthermore, additional comparisons in heat-related health outcomes for vulnerable groups will help provide an intersectional lens to identifying mechanisms for adverse health outcomes. Areas disproportionately vulnerable to heat stress can then be prioritized for greening interventions (The City of New York 2017; Hopkins et al. 2022).
Our emphasis on the importance of community engagement is rooted in the legacy of environmental justice, which requires procedural justice in environmental planning through community outreach and participatory methods (Schlosberg and Collins 2014). While most of the 46 studies fall short when it comes to long-term community engagement methods, some of the studies we analyzed were environmental justice-focused through recognizing vulnerable populations and the distribution of environmental injustice. For example, Gabbe et al. (2023) and Cronley et al. (2024) were focused on examining the experiences of people experiencing homelessness during extreme heat events (Gabbe et al. 2023; Cronley et al. 2024). Other studies compared neighborhoods with different levels of socio-economic advantage (Mittermüller et al. 2021) or specifically focused on areas with socio-economic disadvantage (Bai et al. 2013; Lanza et al. 2023). Finally, multiple studies also focused on analyzing the thermal comfort/heat stress according to older adults who are particularly vulnerable to extreme heat (Yung et al. 2019; Li et al. 2023). Future studies should continue to address the distribution of injustice and recognize who is most affected by injustice while also paving the way for procedural justice for communities in decision-making, all research goals that are aligned with the 3 tenants of environmental justice: distributional, recognitional, and procedural justice (Schlosberg and Collins 2014).
Our findings also underscore the importance of multistakeholder collaboration for teams seeking to limit the health-related impacts of heat waves through green interventions. Transdisciplinary multistakeholder collaboration involves community-specific viewpoints on urban greening and its relation to health, including acknowledgement of the competing interests of communities (e.g., immediate needs about housing, education, healthcare, personal safety) and communication on investing in long-term solutions that will alleviate future climate-related risk. Our results can aid in facilitating transdisciplinary discussions by sharing the various definitions, terms, and methods utilized in the literature to describe urban greening, community engagement, and heat-related health. Shared language is another important factor in operationalizing transdisciplinary research (Cannon 2020).
Finally, our results also revealed limited geographical and climatological reach. There were no studies that met our inclusion criteria from Africa and only one from South America, two continents often underrepresented in urban greening literature, despite increased climate-amplified extreme heat and climate injustice in countries in the Global South (Ogunbode 2022). Additionally, these continents have largely tropical and dry (arid) climates, which were also underrepresented in our findings yet particularly susceptible to climate change-amplified extreme heat (Harrington and Otto 2020; Ehsan et al. 2021). Global environmental and climate justice calls for future research that prioritizes underrepresented countries and climates, using diverse methods of engagement (Ogunbode 2022). These include culturally specific tools including the role of various faith and religious beliefs in community health and urban greening/forestry, a theme notably absent from the analyzed studies. There is a growing body of urban greening literature informed by organized religion that emphasizes stewardship of the earth, trees, and ecosystems as integral to religious beliefs (e.g., Christianity, Islam, and Hinduism) and the interconnectedness of all living beings and the need for harmonious coexistence with nature (Coward 2003; Jusoff and Samah 2011; Gnanakan 2015). This gap reveals a potential research agenda for the future of addressing heat risk, community engagement, and urban greening that extends beyond current equity-focused work (Grabowski et al. 2023).
This paper was limited in that it was a scoping review, which assesses broad themes or gaps in the literature, resulting in a less analytical description of the literature, compared to a systematic review. To include research across disciplines, we had to have broad inclusion criteria with multiple possibilities for inclusion, which may have introduced bias within our screening. Furthermore, while we recognize the expanse of literature in each respective field, our goal was not to be necessarily comprehensive but rather to evaluate the methods and research practices that combine urban greening interventions with community engagement principles to prevent heat-related health effects.
Conclusions
As climate change threats increase, it becomes increasingly important to protect those most vulnerable to extreme heat events. Urban greening interventions have proven to be a sustainable and effective solution to cooling, yet there are few succinct frameworks that guide how to design and maintain urban green spaces with long-term community collaboration and measurable community heat-related health outcomes. Our study aims to inform urban greening researchers on the landscape of the literature to support transdisciplinary, health-focused urban greening.
Our findings therefore come at an urgent time, as climate change risks increase and as urban greening and heat-related public health policies become a priority around the world. In the United States alone, the Inflation Reduction Act invested $1.5 billion to support urban forest expansion, planning, and management, particularly for disadvantaged communities (USDA Forest Service 2023). Multiple cities in the United States have also recently passed legislation that codifies the expansion of the urban forest (City of Chicago 2009; City of Syracuse 2020; Urban Forestry Division 2022; Kiel 2023). As other cities establish similar plans and receive funding for research and implementation, it is even more necessary for planners to have a framework grounded in health equity goals, community-dependent designs, and transdisciplinary collaboration. We hope our discussion on the intersection of urban greening, heat-related health, and communities can help to inform planners so that the cooling health benefits of urban greening can be realized for all.
Acknowledgements
This work was supported by the National Institutes of Health [K08HL163329 Award granted to Dr. Ghosh]; the Cornell Atkinson-Environmental Defense Fund; the Cornell Atkinson Center for Sustainability Academic Venture Fund; and the National Institute on Minority Health and Health Disparities [P50MD017341 Award granted to Dr. Ghosh].
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