Effects of Spatial Pattern of Forest Vegetation on Urban Cooling in a Compact Megacity

TLDR

Urban forests mitigate the urban heat island effect, but understanding which factors govern their cooling intensity is essential for designing effective greenspace networks. This study quantified how spatial patterns of forest vegetation influence urban cooling in Shanghai, China, to guide planners in developing adaptive forest strategies. Using remote‑sensing derived land surface temperatures and eight landscape metrics measured with standard and moving‑window approaches, the authors applied correlation analyses and regression models to assess cooling intensity. Results showed that a 90 m × 90 m scale is optimal, woodland outperforms grassland, larger and more compact woodland patches, higher vegetation coverage, aggregated distribution, and increased shape complexity all enhance cooling, reducing LST in Shanghai’s urban area.

Abstract

Urban forests can be an effective contributor to mitigate the urban heat island (UHI) effect. Understanding the factors that influence the cooling intensity of forest vegetation is essential for creating a more effective urban greenspace network to better counteract the urban warming. The aim of this study was to quantify the effects of spatial patterns of forest vegetation on urban cooling, in the Shanghai metropolitan area of China, using correlation analyses and regression models. Cooling intensity values were calculated based on the land surface temperature (LST) derived from remote sensing imagery and spatial patterns of forest vegetation were quantified by eight landscape metrics, using standard and moving-window approaches. The results suggested that 90 m × 90 m was the optimal spatial scale for studying the cooling effect of forest vegetation in Shanghai’s urban area. It also indicated that woodland performed better than grassland in urban cooling and the size, shape, and spatial distribution of woodland patches had significant impacts on the urban thermal environment. Specifically, the increase of size and the degree of compactness of the patch shape can effectively reduce the LST within the woodland. Areas with a higher percentage of vegetation coverage experienced a greater cooling effect. Moreover, when given a fixed amount of vegetation covers, aggregated distribution provided a stronger cooling effect than fragmented distribution and increasing overall shape complexity of woodlands can enhance the cooling effect on surrounding urban areas. This study provides insights for urban planners and landscape designers to create forest adaptive planning strategies to effectively alleviate the UHI effect.