Green Health: Examining the role of green space characteristics and their proximity in green space health pathways

Examining the role of green space characteristics and their proximity in green space health pathways

Abstract

This doctoral research explores if and how green spaces are able to mitigate the global disease burden of non-communicable diseases (NCDs), by examining the role of green space characteristics and their proximity for three key theorized pathways: (1) The inviting character of green spaces to be more physically active and their health benefits; (2) the ability of green spaces to promote social cohesion and in turn mental health; (3) and the mitigation potential of green spaces to reduce air pollution and their associated health benefits. However, inconsistencies in research methodologies, definitions, and design hamper the synthesis of findings in the green space health research domain. This dissertation aims to bridge these gaps by developing a theoretical and methodological framework examining the proximity to and key characteristics of green spaces, focusing on their role in physical activity, social cohesion, and air pollution health pathways. The main research question is: How do proximity to and characteristics of green spaces affect pathways to human health?

To answer this main research question, the research ties in with the EU Horizon2020 project URBiNAT, an initiative exploring the benefits of nature-based solutions (NBS) in deprived urban areas across Europe. Self-reported data from this project, derived from surveys conducted in the four European cities Nantes, Porto, Sofia and Høje-Taastrup, serves as the foundational dataset for the thesis’ case studies.

In Chapters 2 and 3 the methodological contribution to the research field is presented. It introduces PRIGSHARE (Preferred Reporting Items in Greenspace Health Research) and its complementary open-source script, AID-PRIGSHARE. PRIGSHARE offers a 21-item checklist that aids in the systematic evaluation and comparison of studies, focusing on aspects like objectives, scope, types of green space assessments and context variables. AID-PRIGSHARE simplifies the resourceintensive process of green space assessment by automating the generation of key indicators such as surrounding greenness, accessible green space, green corridors and green space uses within specified distances from 100 to 1,500 m, every 100 m. Jointly, they aim to synchronize research efforts in this field, allowing for more precise and coherent studies while accommodating diverse research designs.

In Chapter 4 the empirical findings reveal key relationships between green space characteristics within walkable distances, with physical activity and health. A main outcome is that residing near green spaces, especially green corridors with diverse uses within 800 m, or a 10-minute walk, was associated with higher physical activity and indirect health benefits. However, a higher quantity of green space uses and greater surrounding greenness at larger distances (1,100–1,500 meters) showed a negative correlation with physical activity and health, which could be related to the increased car-dependency of greener or more rural districts. While this research focuses on four European so-called satellite districts, it underscores the importance of proximity and green space characteristics in the green space health research field. It concludes by emphasizing the value of interconnected, multi-use green spaces, given their potential to combat physical inactivity and its associated health risks.

Chapter 5 discusses the empirical findings on the green space mental health associations through increased social cohesion. The study found that certain green space characteristics are linked with elevated levels of social cohesion, which in turn appear to favour mental health outcomes. Specifically, accessible greenness (including vegetation along streets) and green spaces within a surrounding area of up to 1,500 meters, green corridors in an intermediate surrounding of up to 800 meters, and mix of use in green spaces measured in 700 to 1,300 meters, showed significant indirect associations to mental health. However, the study found no direct positive effects of any green space variables on mental health, suggesting that the benefits are fully mediated by social cohesion. These insights into how and where these mechanisms occur provide important evidence for urban planners and public health decision-makers on the importance of how to design neighbourhood green spaces to foster social cohesion and mental health.

Chapter 6 reveals the empirical findings about the green space health associations that are mediated through lower air pollution. In this study, only two green space characteristics were associated with indirect health effects through lower selfrated air pollution. First, the area of green corridors measured in intermediate surroundings of 800-1,000 m was significantly related to experiencing lower air pollution and indirect health effects. Second, accessible green spaces were also associated with lower self-rated air pollution and indirect health effects at network distances of 1,400-1,500 m. These findings support the idea that the connectivity of green spaces is vital for mitigating air pollution. These findings offer important support for urban planners aiming to reduce air pollution and its associated health risks, suggesting to focus on interconnected green networks.

In concluding Chapter 7, the results are synthesised to present several key insights that have broad implications for urban planning, public health policies, and future green space research. Despite its limitations of self-reported data, cross-sectional study design and constraints in model complexity, the synthesis of the results of the individual studies in this doctoral research indicates distinct thresholds for distances in which every pathway operates and which green space characteristics are the driving features of those mechanisms. For future research, these new insights offer a foundation to examine causality or more complex pathway chains. For practitioners, it makes a strong case for designing connected, multifunctional green space corridors rather than isolated patches, to optimize positive health outcomes associated with green spaces. These insights not only contribute to WHO’s Urban Health Research Agenda but also offer specific, actionable recommendations that could profoundly impact public health promotion strategies aimed at combating noncommunicable diseases (NCDs).