Large-scale greenway intervention promotes walking behaviors: A natural experiment in China
Introduction
Physical inactivity has gradually become a severe public health issue, one that increases the risk of disease and imposes a significant burden on healthcare systems (Ding et al., 2016). Despite it being well-established that physical activity contributes substantially to physical and mental health (Tessier et al., 2000, Lee et al., 2012, Hegde and Solomon, 2015), average levels of weekly physical activity among adults in China declined by 31% between 1991 and 2011 (Ng et al., 2014). One-third of adults fail to meet the recommended physical activity level (WHO, 2020).
Walking provides a vital opportunity to increase energy expenditure and does not require specific skills or equipment (Hogendorf et al., 2020). Reviews supported by meta-analysis reveal that people’s walking behavior is associated with different urban environmental features, including urban density, street connectivity, destination accessibility, and greenspace infrastructure (Ewing and Cervero, 2010, Wang and Zhou, 2017). Whilst predominantly derived from cross-sectional studies (Wang et al., 2021), and susceptible to methodological limitations, the environmental interventions have been advocated to sustain and improve people’s opportunities to walk (Liu et al., 2016). However, the rationale for investing in specific urban infrastructures remains insufficient (Cohen et al., 2013, Craig et al., 2017). To support evidence-based policy-making, more robust research designs are needed to ensure scientific rigor (Craig et al., 2017, Sun et al., 2020).
Urban greenspaces (e.g., parks, tree-lined streets trees, and greenways) provide safe and attractive places for urban dwellers to participate in healthy activities (Lu et al., 2021, Roux et al., 2007, Yang et al., 2019). Urban greenways are usually considered to be landscaped and traffic-calmed pathways that link parks, open spaces, and public facilities. They are generally planned for multiple purposes (e.g., transportation and recreation) (Horte & Eisenman, 2020), and support a variety of active travel uses (e.g., walking and bicycling) (Ngo et al., 2018, Dallat et al., 2014). Evidence from several cross-sectional studies suggests that creating greenways and making them more accessible are positively associated with walking behaviors (Liu et al., 2016, Astell-Burt et al., 2014).
However, rigorous evidence cannot be established by cross-sectional studies alone because, for example, they are subject to reverse causation and can address self-selection in only a limited way (Yang et al., 2021). This limitation arises because people who have positive attitudes towards walking select to live in greener neighborhoods thus walk more (Guan et al., 2020, Beenackers et al., 2012, Cao, 2015). Consequently, assuming that people intentionally live in their preferred residential environment, the greenway–walking associations cited were probably spurious; that is, observed higher walking levels may have been determined by people’s attributes rather than by better access to greenspaces (Gubbels et al., 2016).
Given the inherent limitations of cross-sectional designs, interest in the use of natural experimental design to better establish causal relationships is growing (Sallis et al., 2009, Veitch et al., 2012, Hirsch et al., 2014). The primary purpose of such designs is to manipulate a treatment variable (e.g., an intervention) and a time variable (e.g., pre- and post-intervention) to determine their causal effect on outcomes (Leatherdale, 2019). Although purely experimental designs (i.e., a randomized controlled trial) are methodologically the most rigorous, they are seldom possible as it is usually impractical for researchers to manipulate an external intervention (e.g., the creation of a greenway) and/or randomly assign people to an experimental group or a control group (Dunning, 2008, Cohen et al., 2013).
An alternative yet robust natural experimental research design was advocated to evaluate the effects of built environment interventions on healthy behaviors (Leatherdale, 2019). In natural experimental studies, the interventions naturally occur, rather than being manipulated by researchers. Such studies typically compare the behavioral changes of nearby residents before and after a greenway creation with those of their counterparts living further away (Hunter et al., 2015). For instance, some studies confirm that the exposed group exhibited significant increases in overall physical activity after a greenspace intervention, relative to the control group (Huston et al., 2003, Frank et al., 2019). Whilst dichotomous measures (exposed vs. unexposed) provided causal evidence, in-depth insights into how changes in residents’ behaviors possibly decline with increasing geographic distance from the greenway remain limited (Frank et al., 2019). In response, some studies stressed the need to decode the dose–response function by measuring the residential proximity across multiple distance bands (Xie et al., 2021).
Socio-ecological models capture interdependencies among personal and environmental factors (Gubbels et al., 2016). For example, people with low socio-economic status (SES) may not have sufficient financial means to afford private greenspaces and thus rely more heavily upon the provision of public spaces (Lachowycz & Jones, 2013). However, as shown elsewhere (Wolch, Byrne, & Newell, 2014), greenspaces are generally disproportionately distributed and predominantly benefit affluent neighborhoods (Rigolon et al., 2021). Constrained by safety concerns and a lack of leisure time, women are more sensitive to distance to greenspaces, especially during early motherhood, compared with men (Lee et al., 2001, Bedimo-Rung et al., 2005). Similarly, older low-mobility adults are also sensitive to the distance to a greenspace (Maas et al., 2009). Congruent with environmental justice and social equity literature (Xiao et al., 2017), greenspace should be seen as a public good that is available to everyone, and comprehensive approaches were proposed to address relevant issues.
A series of studies have suggested that creating accessible public greenspaces may combat environmental injustice, especially in deprived neighborhoods (Wolch, Byrne, & Newell, 2014). The logic here was that privately-owned greenspaces were predominantly used by privileged people, and vulnerable groups tended to have limited access to greenspace. Investing in public greenspaces may effectively alleviate the unequal distribution and increase their exposure opportunities to greenspace. Thus, providing accessible, well-maintained, and safe greenspace for vulnerable groups has become a common goal in different countries (Xiao et al., 2017). However, prior observations were limited by their scientific rigor, and longitudinal evidence concerning whether vulnerable groups can get more health and social benefits through greenspace intervention remained unclear (Hunter et al., 2015).
Prior studies on this topic faced the following limitations. First, previous interventions were limited in scale, because the investigated greenway projects were typically within a few kilometers of distance (Frank et al., 2019). Second, most studies used a single distance threshold to define greenway exposure (vs. non-exposure) (West & Shores, 2015). Such a dichotomous measure failed to capture either distance-sensitive effects of greenway interventions on walking or the distance decay of the delivered benefits. Third, these natural experiments predominantly focused upon overall physical activity rather than on walking behaviors (Frank et al., 2019). Overall physical activity levels may not correspond well to domain-specific physical activities (Hogendorf et al., 2020). Fourth, earlier studies paid limited attention to whether the effects of greenway interventions vary across different socio-demographic population strata (e.g., socially disadvantaged groups, older adults) (Gubbels et al., 2016).
To fill these research gaps, our primary goal was to quantify the effects of a large-scale transportation infrastructure (i.e., East Lake greenway) on the walking behaviors of nearby residents by conducting a natural experiment. Our secondary aim was to assess the dose–response effects of such an intervention and determine its catchment area by a novel method to define greenway exposure. Finally, we examined whether the walking-promoting effects of the greenway intervention varied across socio-demographic and socio-economic population strata, in order to ascertain whether the intervention reduced social inequities associated with physical activity.
Section snippets
Study area
Wuhan has a population of 11.2 million (2019) and is the economic center of Central China (Wuhan Municipal Statistics Bureau, 2020). Due to the presence of numerous bodies of water, Wuhan is also known as the “city of hundreds of lakes”. One of these —East Lake, which is located in the metropolitan center—is the largest urban lake in China (Fig. 1).
The East Lake greenway intervention
The East Lake greenway was developed in 2016–17. The first phase (28.7 km in length) was opened to the public in December 2016, and the remaining
Descriptive analyses
Table 2 shows descriptive summary statistics. Paired t-tests indicate significant differences in the changes in weekly walking time across both waves (p < 0.001). The walking time of participants living within 2 km of the greenway increased significantly at follow-up, whereas changes in the walking time of participants living 2–5 km from the greenway are insignificant. For individual characteristics, the attributes of groups with different residential proximity to the greenway show no
Key findings and their interpretation
Numerous cities in China have recently developed different types of public greenspace to support healthy urban living (Liu et al., 2016), but few studies have examined the actual health benefits originating from such interventions. To provide rigorous evidence on walking behaviors, we selected a typical greenway intervention project in Wuhan, China.
Our analysis led to three main findings. First, our results showed that the greenway intervention significantly increased people’s weekly walking
Conclusion
Our robust findings based on mixed-effect difference-in-difference regressions showed that the greenway intervention (i.e., the opening of East Lake greenway in Wuhan, China) increased the weekly walking time of nearby residents, and the catchment area extended to two kilometers from the intervention. Furthermore, the walking-promoting effects of the intervention were more pronounced among women and socio-economically disadvantaged people.
Funding
Thanks to the funding support of the National Natural Science Foundation of China (No. 41971179 & 51778552) and the Research Grants Council of the Hong Kong SAR (Project No. CityU11207520).
Ethics approval
Ethical approval for the study was obtained prior to this study from the Research Committee of City University of Hong Kong (No. H000691). All participants provided written informed consent.
CRediT authorship contribution statement
Dongsheng He: Methodology, Formal analysis, Visualization, Writing – original draft. Yi Lu: Conceptualization, Methodology, Supervision, Writing – review & editing. Bo Xie: Conceptualization, Data curation, Methodology, Supervision, Writing – review & editing. Marco Helbich: Writing – review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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