2.2.2. Global artificial impervious areas
Artificial impervious areas are predominant indicators of human settlements. Timely, accurate and frequent information on the artificial impervious areas is critical for understanding the urbanization process and the land use/cover change, as well as their impacts on the environment and the biodiversity. Based on the full archive of the 30-m resolution Landsat images on the Google Earth Engine platform, the annual global artificial impervious areas (GAIA) are mapped from 1985 to 2018 (Gong, Li et al. 2020). With the ancillary datasets, including the nighttime light data and the Sentinel-1 Synthetic Aperture Radar data, the performance of our previously developed algorithm is improved in arid areas. The GAIA dataset can be freely downloaded from http://data.ess.tsinghua.edu.cn.
The GAIA data with a spatial resolution of 30 m from 2000 to 2018 are used in this study to investigate the urbanization development over the LP during this period (He, Yang et al. 2020). According to the GAIA data in 2018 and 2000, there are six UAs over the LP, including Xi’an, Taiyuan, Luoyang, Hohhot, Yinchuan and Xining-Lanzhou (Fig. 1). The artificial impervious area in Xi’an, Taiyuan, Luoyang and Hohhot reached 1400 km2,1700 km2, 1000 km2 and 1000 km2 in 2018, which is 2 times, 2 times,1.5 times and 1.5 timesthat in 2000, respectively (Fig. 2). Due to the relatively slow economic development, the artificial impervious area in Yinchuan, Xining and Lanzhou only increased by 100–200 km2 in 2018 compared to 2000.