Different types of urban natural environments influence various dimensions of self-reported health
Introduction
The world is increasingly urbanised (United Nations, 2019) and the shift from rural to urban living environments affects individuals’ health in many ways. While urban living is associated with opportunities, such as access to jobs and healthcare services, urban areas are also characterised by more crowded, polluted and stressful living environments and often greater social disparities as compared to their rural counterparts (Lavin et al., 2006). Furthermore, mental health disorders are more common in cities than in rural populations (Lederbogen et al., 2011). These urban trends are serious threats for public health.
A large and growing body of evidence demonstrates the potential of urban natural environments in tackling a wide variety of public health concerns (Hartig et al., 2014). Natural environments take the form of greenspaces (e.g., forests, street trees, gardens, agricultural crops) and blue spaces (e.g., ponds, lakes, rivers, oceans). Research suggests that urban natural environments can reduce the risk of cardiovascular disease (Donovan et al., 2015), cognitive and behavioral disorders (Dadvand et al., 2015), mental health complaints and disorders (Annerstedt et al., 2012), and all-cause mortality (Crouse et al., 2017); though, there is some inconsistency in findings (Zock et al., 2018). Moreover, urban nature can increase the odds of improved self-reported health and well-being (de Vries et al., 2003; Maas et al., 2006; Mears et al., 2019; Triguero-Mas et al., 2015). Natural environments are hypothesized as promoting health through several pathways, including reducing stress, providing spaces for physical activity, and creating opportunities for improved social capital (Markevych et al., 2017). In addition, urban ecosystem services can mitigate harmful environmental exposures (Millennium Ecosystem Assessment, 2005), such as excessive heat (Graham et al., 2016).
While the majority of findings report positive associations between natural environments and health, several reviews indicate inconsistency in results and insufficient evidence (Gascon et al., 2015; Houlden et al., 2018; Kondo et al., 2018; Twohig-Bennett and Jones, 2018; van den Berg et al., 2015; van den Bosch and Ode Sang, 2017). It is plausible that the lack of consistency in findings may in part be due to the simplified characterisation of urban environments and relatively crude greenspace indicators (e.g., Normalized Difference Vegetation Index (NDVI)) that do not take different types of natural environments into account, as well as the range of approaches used to estimate human-nature contact across studies.
Despite the variety of forms natural environments may take, most studies have considered natural environments as aggregated “green” spaces, with few studies exploring potential differences in effect depending on the type of natural environment. Conceivably, different types of natural environments may vary in their capacity to promote health depending on pathways most likely to support a health outcome. For instance, forests may provide more shade and thus greater reductions in surrounding air temperatures and heat-related morbidities as compared to open greenspace, such as grasslands, which lacks tree canopy cover.
Existing research has measured human contact with nature in a variety of ways. Generally, studies use metrics for either access or exposure (Ekkel and de Vries, 2017; Jarvis et al., 2020). Access metrics typically estimate the proximity of an individual’s residence to public natural environments, whereas exposure metrics typically estimate the relative proportion of natural environments surrounding an individual’s residence. Despite evidence suggesting that access to public greenspace is only weakly correlated with exposure to natural environments (Jarvis et al., 2020), little attention has been paid to the potential differences between these metrics. The majority of published work has focused exclusively on evaluating a single metric, without clear consideration of how the choice of metric may affect the association with different health outcomes. It is possible that the pathways linking natural environments to health outcomes differ between these two metrics. For example, access to nearby public natural environments may improve health through providing opportunities for social interactions and physical activity, whereas daily residential exposure to nature may provide regulating ecosystem services, including the reduction of noise and air pollution.
Only a limited number of studies have addressed potential gender differences in associations between natural environments and health. The few research findings that exist provide mixed evidence. Some research report stronger beneficial effects of natural environments for women (Reklaitiene et al., 2014; Roe et al., 2013) and others for men (Richardson and Mitchell, 2010). On the other hand, van den Berg et al. (2016) found no gender differences in health effects associated with visiting greenspaces. Reported variation in health associations between men and women may stem from gender-related differences in perceptions and use of natural space. For instance, studies suggest that women’s engagement with natural environments is more strongly affected by societal norms (e.g., spending more time at home) and perceived barriers to use (e.g., quality and safety), as compared to men (Kavanagh et al., 2006; Ward Thompson et al., 2005).
The present study evaluates the association between different natural environments and self-reported general health, mental health, and common mental disorders, respectively. We address current gaps in the literature by evaluating exposure to different land cover types (both land and water features) and their association to health outcomes. We also aim to assess potential differences in associations with health outcomes by investigating relationships with access or exposure to nature. Lastly, we evaluate whether observed associations differ according to gender. Specifically, the present study addresses the following research questions:
- 1.
How is an individual’s self-reported health associated with exposure to natural environments in their residential area?
- 2.
Do any observed associations between an individual’s self-reported health and nature exposure differ according to land cover type?
- 3.
How is an individual’s self-reported health associated with their access to public greenspaces?
- 4.
Do any observed associations between natural environment metrics and self-reported health differ according to the individual’s gender?
Section snippets
Study area and sample
This study was conducted in Metro Vancouver, Canada. Metro Vancouver is the third largest metropolitan area in Canada, comprising over 2.5 million residents (Statistics Canada, 2017). The region covers 2,883 km2 of land area and has a population density of approximately 855 persons/km2 (Statistics Canada, 2017). Approximately one third of the region is designated as urban (e.g., residential, commercial, industrial) and the remaining area is characterized by diverse land cover and land use
Study sample characteristics
After excluding missing data, a weighted sample of 1,960,575 respondents had matched natural environment data and valid responses for the outcome and confounder variables (see Fig. 1 of Supplementary Material). Descriptive statistics for the study sample and outcomes are presented in Table 1. Two-thirds of the sample was 25 to 64 years of age (66.2%). Half of the sample described themselves as white (50.7%) and approximately one third as East Asian (29.5%). The majority of respondents had
Discussion
We assessed the relative influence of different types of natural environments and forms of human-nature contact on self-reported general health, mental health, and common mental disorder. We found that associations between exposure and health outcomes varied according to land cover type. Specifically, exposure to water and some vegetation types, in particular shrubs and grass-herbs, was associated with reduced odds of poor self-reported health; the reverse trend was observed for exposure to
Conclusions
Our study contributes to an improved understanding of the potential role of land cover type in associations with public health outcomes and suggests that exposure to certain types of nature may be more beneficial than access to public greenspace. Our findings also suggest that observed associations between human-nature contact and self-reported health may differ according to gender. Consistent with published work, the strength of observed associations between natural environments and health
Funding sources
This work was supported by the Natural Sciences and Engineering Research Council of Canada [grant number 538545]; and the Canadian Institutes of Health Research [grant number 156152].
Ethics
This research received initial and ongoing ethics approvals from the University of British Columbia’s Behavioral Research Ethics Board [project number H17-01687].
CRediT authorship contribution statement
Ingrid Jarvis: Conceptualization, Methodology, Formal analysis, Investigation, Data curation, Writing - original draft, Writing - review & editing, Visualization, Funding acquisition. Mieke Koehoorn: Methodology, Investigation, Writing - review & editing, Supervision. Sarah E. Gergel: Methodology, Writing - review & editing, Supervision. Matilda van den Bosch: Conceptualization, Methodology, Investigation, Writing - review & editing, Supervision, Funding acquisition.
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.
Acknowledgements
The data analysis for this paper was generated using SAS software. Copyright © 2013 SAS Institute Inc. SAS and all other SAS Institute Inc. product or service names are registered trademarks or trademarks of SAS Institute Inc., Cary, NC, USA.
The land cover map was provided by Metro Vancouver. Normalized Difference Vegetation Index (NDVI) metrics, indexed to DMTI Spatial Inc. six-digit postal codes, were provided by CANUE (Canadian Urban Environmental Health Research Consortium).
This research
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2023, Environmental ResearchCitation Excerpt :In contrast, the association between grass and self-reported health was insignificant. Other studies also reported that tree canopy and shrubs/forbs coverage often showed more consistent associations with health outcomes than grass (Jarvis et al., 2020; Browning et al., 2019; Zhang and Tan, 2019). As illustrated in Fig. 6, we argue that trees and shrubs/forbs might have greater ecosystem functions in reducing harm such as air pollution, noise, and heat (Nowak et al., 2006; Abhijith et al., 2017; Klingberg et al., 2017) and increasing biodiversity (Marselle et al., 2020; Liu and Slik, 2022) than grass.
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2022, Science of the Total EnvironmentCitation Excerpt :Our results based on the NDVI indicator of greenness, that did not account for the different type of vegetation, supported an overall beneficial effect of greenspace on MCS. However, the type of vegetation might be important as suggested by previous studies (Jarvis et al., 2020) and by our results supporting a beneficial impact of exposure to forest while exposures to urban green space and agricultural land were not associated with MCS. The beneficial effect of greenspace exposure on mental health could be mediated by behavioural factors (e.g. encouraging physical activity), social factors (e.g. fostering social contact), direct mental health effects (e.g. decreasing stress) or correlated environmental factors (e.g. lower air pollution, noise and heat) (Markevych et al., 2017).