Abstract
With the acceleration of urbanization, the changes in urban environments have resulted in complex public health challenges. Urban green spaces as key components of urban ecosystems and green infrastructure positively contribute to public health by improving air quality, reducing stress, and promoting social interactions. Both the World Health Organization (WHO) and the United Nations Sustainable Development Goals (SDGs) emphasize creating greener, safer, and more inclusive urban environments to improve residents’ health. In this context, sufficient “exposure” to green spaces is considered as a fundamental prerequisite and an essential strategy for realizing health benefits. However, in the complex urban context, the development of urban green spaces is often constrained and unevenly distributed, limiting their potential to deliver equitable health benefits. Therefore, it is necessary to explore the underlying mechanisms linking green exposure to health outcomes, thereby providing a scientific foundation for integrating these insights into health-oriented urban green space planning practices.This study focuses on the relationship between urban green exposure and human health, using Xiamen and Shanghai as study areas. By integrating diverse geospatial data (topography, vegetation distribution, building elevation), population health questionnaires, and location-based service big data (Baidu Map location data), research is conducted from three dimensions of green exposure visibility, accessibility and availability, as well as three health dimensions of physical, mental and social. The research content includes quantitatively assessing the association between green exposure and health, identifying the threshold range of green exposure that generates significant health benefits, revealing the factors influencing the supply of green exposure in complex urban environments, and evaluating the matching status between the supply of green space exposure and the demands of the population and proposing optimization strategies. The main contents are as follows:
(1) Based on the residential locations of 902 investigated individuals in Xiamen, the green exposure was quantified according to the 3-30-300 green space rule (at least 3 trees visible from home, neighborhood canopy coverage of at least 30%, and 300 m to the nearest green space). Residents meeting the "30" criterion exhibited significantly improved physical health (β=0.76, p<0.05) and social health (β=0.5, p<0.05). The local results indicated that in relatively less developed urban areas, meeting only the "3" criterion led to significant declines in both physical and mental health (β=-2.26 to -1.16, p<0.05). Overall, green exposure provides more significant health benefits in urban areas with developed infrastructure, and socioeconomic pressures and other demographic factors may overshadow the health outcomes.
(2) The quantitative analysis of the nonlinear relationships between green visibility, accessibility, and proximity and their associated health effects reveals the presence of threshold effects in green exposure. In Xiamen, the health benefits of green visibility begin to emerge when it reaches 10%, with optimal effects observed at 15%. For green accessibility, health benefits start to appear at 26%, reaching an optimal level at 35%. However, no threshold was identified for green proximity. Overall, the identification of thresholds provides valuable insights into the minimum and optimal levels of different green exposure pathways necessary to achieve health benefits.
(3) The global and local impacts of built form compactness and soil physical and chemical properties on the comprehensive green exposure supply were explored through 2,966 living circle units in Shanghai. The results indicate that, at the global scale, higher built-up compactness is significantly associated with lower levels of green exposure (β = –0.16 to –0.09, p < 0.001). The fertility of the surface soil has a positive effect on green exposure supply. In contrast, excessive nutrient elements such as total nitrogen (TN) and total phosphorus (TP), as well as higher bulk density, have a significant inhibitory effect on green exposure in deeper layers (β = -0.40 to -0.82, p < 0.001). Therefore, green exposure should be implemented differently based on the specific soil-built environment characteristics of urban contexts.
(4) By integrating traditional green exposure (TGE) with the actual intensity of green space use, Human Activity Green Exposure (HAGE) was formed, and the supply and demand relationship of green exposure was explored in 2,966 living circle units in Shanghai. Results showed an inverted U-shaped spatial pattern of HAGE in Shanghai, with moderate positive autocorrelations between HAGVI and TGVI (Moran’s I=0.45, p<0.01). HAGAC and TGAC exhibited a weaker autocorrelation (Moran’s I=0.24, p<0.01), whereas HAGAV and TGAV showed none. The LISA map further revealed locations where green exposure did not align with green coverage, indicating that more greening does not always equate to increased human exposure. Abnormal clustering areas indicated fragmented green spaces, mismatch with human activities, or insufficient configuration to meet residents’ needs.
Overall, this study clarifies the associations between different urban green exposure pathways and multi-dimensional human health, while highlighting spatial variations. Furthermore, it introduces an innovative quantitative assessment approach based on a GIS framework to more accurately measure residents' actual green exposure levels. All results provide empirical evidence and scientific support for health-oriented urban green space planning.
| Date of Award | 15 Nov 2025 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Nicholas Hamm (Supervisor), Tongyu Zhou (Supervisor), Yongguan Zhu (Supervisor) & Tao Lin (Supervisor) |