Spatiotemporal evolution of urban green space and its impact on the urban thermal environment based on remote sensing data: A case study of Fuzhou City, China

Abstract

Taking the main city of Fuzhou as the study area, the relationship between the spatiotemporal evolution of urban green space (UGS) and the urban thermal environment from 1993 to 2013 was investigated using a set of remote sensing images. The evolution of UGS is obvious in the study area, where UGS loss (42.83 km2) > UGS extension (4.99 km2) > UGS exchange (2.61 km2). UGS loss affects forest/grass > water > wetland. Furthermore, the area defined as high temperature zones increased by 23.11 km2 in 2013, twice as much as that in 1993. However, the influence of UGS on the urban thermal environment differs by type and evolution: water has the greatest cooling effect, followed by wetland and forest/grass, and UGS loss (8.67 ℃) > UGS exchange (4.00 ℃) > UGS extension (2.90 ℃) > UGS unchanged (2.45 ℃). Finally, the vegetation and cooling index classified the mechanism of temperature response induced by different types of UGS evolution. The evolution of UGS loss usually simulated the movement of the corresponding pixel from the low land surface temperature and high vegetation coverage to the opposite situation. Regression analyses demonstrated that the effect of elevated land surface temperature generated from the reduction of water and forest/grass reached 0.81 ℃ and 0.72 ℃, respectively, in 20 years, indicating that the loss of a significant amount of UGS during urbanization was the primary influence on the urban thermal environment. This study may provide more useful information for researchers and decision-makers engaged in urban planning, urban regeneration, and sustainable land development, especially focusing on the issues of climate adaption and the urban heat island (UHI) effect mitigation.