Inequalities in urban thermal and greenspace exposures: A case study for China's Greater Bay Area from 2010 to 2020

The interaction between humans and their environment significantly impacts the health of urban residents. However, there is limited research on assessing the spatiotemporal variations of human thermal exposure as well as inequalities and their relationships with greenspace based on remote sensing data, especially in developing countries. This study offers a framework utilizing pixel-wise data on land surface coolness index (LSCI), normalized difference vegetation index (NDVI), and population metrics to evaluate population-weighted thermal and greenspace exposures in China's Greater Bay Area (GBA) over eleven years (2010-2020). It further examines thermal exposure inequality using the Gini index and explores both natural and socio-economical drivers of thermal exposure and its inequality. The results indicate an increasing trend of cities within the GBA being experiencing detrimental thermal conditions. Over the study period, the proportion of cities with high exposure to LSCI and NDVI exhibited a general decline. Approximately 63.6% of major cities observed growing imbalances in LSCI and NDVI exposures over eleven years. Notably, there were positive correlations between NDVI exposure and LSCI exposure, along with their associated inequalities. Moreover, coastal cities characterized by lower elevations, higher precipitation rates, and rapid economic growth experienced higher levels of LSCI and NDVI exposures yet these cities also demonstrated greater disparities.