Effects of green space dynamics on urban heat islands: Mitigation and diversification

Abstract

Understanding how green spaces affect urban temperature is crucial for assessing thermal benefits of landscape planning. This study investigated green space dynamics and land surface temperature (LST) in the Beijing metropolis. Landscape types were classified from QuickBird (2002) and IKONOS (2012) images and LST values were extracted from Landsat TM images. Five landscape types were obtained in this region including impervious land (IL), forest land (FL), grass land (GL), water body (WB), and bare land (BL). Green expansion indicated landscape change from IL and BL to FL and GL. Green loss indicated landscape change from FL and GL to IL. Green exchange indicated landscape change between FL and GL. Results show that (1) the area of green space dynamics accounted for 38.24% of the total research area, including green space losses (108.86km2), expansion (92.49km2), and exchange (53.83km2). (2) LST change was not significant in the unchanged (0–0.19°C) and exchanged green space (in the range of −0.02–0.25°C). However, there were minor decreases of LST in areas of green expansion (in the range of −1.11°C to −0.67°C) and major increases in LST in the areas of green losses (1.64–2.21°C). The results indicated that the number of green spaces is not the only criteria that should be assessed for temperature mitigation. Ecosystem services of temperature mitigation are not equal between the loss and expansion of green spaces even within same area. Greater focus on protecting natural forests in cities might provide greater benefits for climate mitigation.