Urban expansion, ecological environmental quality, ecological evaluation index, spatiotemporal evolution, Pearl River Basin, Mathematical geography. Cartography, GA1-1776, Geodesy, QB275-343

Economic globalization has promoted to rapid urban expansion within the Pearl River Basin, leading to the degradation of the Ecological Environmental Quality (EEQ). This study aims to analyze the spatiotemporal evolution of EEQ in the Pearl River Basin under rapid urbanization period (from 2000 to 2020). A Modified Comprehensive Ecological Evaluation Index (MCEEI) that integrates the anthropogenic pressure index, biological richness index, vegetation cover index, land surface temperature, and surface relative humidity was proposed to address this issue. It was found that, since 2000, the overall EEQ of the Pearl River Basin has declined gradually, and the regions with a low EEQ are primarily located in the central areas of large cities (e.g. Nanning, Liuzhou, Guilin, Guangzhou, Foshan, and Shenzhen). Due to the “Grain for Green Project” policy (China’s nationwide program which pays farmers to revert sloping or marginal farm land to trees or grass), 11.11% of the land area in the Pearl River Basin experienced an improvement in EEQ from 2000 to 2010. However, the rapid expansion of urban areas accelerated the degradation in EEQ, and 22.62% of the EEQ degradation areas occurred in the urban areas from 2010 to 2020. Additionally, as human activities extend into mountainous areas, the proportion of poor and failing EEQ in mountain areas have increased rapidly. Our findings provide guidelines for ecological civilization construction and the protection of the ecological environment in the Pearl River Basin.