Urban Renewal Makes Cities More Livable-An Empirical Study of Fuzhou City from the Perspective of Thermal Environment

Urban renewal is not only a transformation in urban development models but also a shift in urban governance approaches. Implementing urban renewal initiatives is a crucial component of the new urbanization strategy. After experiencing rapid urbanization characterized primarily by "extensive expansion," Chinese cities are gradually shifting toward "intensive development," entering a stage of optimizing existing urban stock through renewal. As a new engine for promoting high-quality urban development, urban renewal is increasingly becoming a key force in optimizing urban spaces and enhancing people's quality of life. It serves as a vital means to advance modernization and achieve the construction of livable cities. Clarifying the thermal environmental effects of urban renewal and their driving mechanisms can provide targeted management strategies for improving urban thermal environments and enhancing livability.

This study focuses on renewal areas within Fuzhou's built-up zones where significant changes have occurred in building structures while the underlying surfaces remain impervious. We analyzed the spatiotemporal distribution characteristics of heat island intensity at key time nodes and the changes in heat island patterns within the renewal area. Additionally, the differences in thermal environmental effects across different types of urban renewal areas at the block scale have been quantified. On this basis, we explored the driving mechanisms of these thermal environmental effects.

The main findings are as follows: (1) From 2000 to 2022, the urban renewal area of Fuzhou City covered approximately 67 km², with the renewal zone concentrated in the old urban area. Renewal during this period mainly focused on the transformation from high-density mid-to-low-rise buildings to low-density mid-to-high-rise buildings, as well as the transformation of industrial sites.

(2) The spatial distribution of changes in urban heat island intensity aligns closely with urban development types. Areas where heat island intensity weakens are mainly concentrated in urban renewal zones, while areas where it strengthens appear in urban expansion zones. The distribution of extremely strong heat islands shows a migration trend from northwest to southeast, consistent with Fuzhou’s urban development strategy.

(3) Overall, urban renewal has improved the thermal environment of Fuzhou. The average intensity of the urban heat island in the updated area decreased by 1.00°C. The primary change in heat island intensity was the transition from extremely strong heat islands to lower intensity categories, effectively mitigating extreme thermal risks.

(4) The analysis of driving mechanisms shows that the thermal environmental effects of urban renewal are driven by the interaction of the water vapor index (NDMI), vegetation index (NDVI), bare soil index (BSI), building coverage rate (BCR), building height (BH), POI mixture degree, and distance to adjacent green spaces and factories. Among these, BSI and BCR are the main driving forces for the increase in heat island intensity, while BH, POI mixture degree, and distance to adjacent factories are the primary factors driving the decrease in heat island intensity.