Global-scale changes in the area of atoll islands during the 21st century

Abstract

The long-term persistence of atoll islands is under threat due to continued sea level rise driven by anthropogenic climate change. One widely discussed potential impact of sea level rise is the widespread, chronic erosion of atoll islands. Despite concerns of erosion driven by sea level rise, no published evidence exists of pervasive erosion of atoll islands at a global scale. Existing studies of atoll island change have been based on small, temporally sparse samples of islands on a limited number of atolls. As a result, the global response of atoll islands coincident with sea level rise remains uncertain. Using rich collections of Landsat imagery, this study analyses changes in land area on 221 atolls in the Indian and Pacific Oceans. Results show that, between 2000 and 2017, the total land area on these atolls has increased by 61.74 km2 (6.1 %) from 1007.60 km2 to 1069.35 km2. Most of the change in land area resulted from island building within the Maldives and on atolls in the South China Sea. Since 2000, the Maldives have added 37.50 km2 of land area, while 16.57 km2 of new islands have appeared within the South China Seas Spratly and Paracel chains. Understanding the extent of land area change at the global scale improves insights into the variation in responses, and how the manipulation of land is shaping the potential habitability trajectory for some atoll communities. Results highlight the anthropogenic imprint on the size of atoll islands, thereby providing a better understanding of variations in the future trajectories of human settlement and adaptation within atoll settings.