Variations of shoreline and land use in Guangdong-Hong Kong-Macao Greater Bay Area from 1989 to 2021

Using 7 periods of the Landsat TM/Sentinel-2 MSI remote sensing image data from 1989 to 2021 with the help of Google Earth Engine (GEE) platform, we extracted 7 periods of shoreline information from Guangdong-Hong Kong-Macao Greater Bay Area using the Modified Normalized Difference Water Index (MNDWI), Canny edge detection algorithm, and remote sensing interpretation classification method. The spatial and temporal characteristics and drivers of shoreline evolution were analyzed in terms of shoreline length, intensity of change, shoreline diversity, shoreline land area change, and shoreline land use change. The results show that: ① The shoreline length of the Greater Bay Area continued to increase from 1989 to 2021, with the total increase of 243.28 km. The variation intensity of shoreline evolution was in phase: slow growth before 2004, and fast growth after 2004 during which 2004—2009 was the fastest period. ② The shorelines in each region of the Greater Bay Area varied to some extents, of which Zhuhai, Hong Kong, Shenzhen and Macao had the greatest shoreline changes while other regions were relatively stable. ③ From 1989 to 2021, the shoreline types changed significantly as artificial shorelines grew notably, which gradually replaced the natural shorelines as the main body of shorelines. The artificial shorelines were increased by 651.17 km in total at the high rate of 172.21%, while the natural shorelines were decreased by 407.89 km. ④ During the study period, the area of land was extended significantly in the Greater Bay Area by 492.80 km² with a fast growth rate of 15.4 km²/a, and the type of land use in the shore zone shifted remarkably from forest land, grassland, and water to construction land and farming land. ⑤ Human activities such as sea-farming, port construction, and land reclamation were the main causes of shoreline changes in the Greater Bay Area; and the natural environmental conditions and anthropogenic activities were the important drivers of shoreline evolution in the Greater Bay Area.