Since the 1980s, the issues of sea-level rise and climate and weather change caused by global warming have been discussed as global issues, and since the 1990s, small island societies in the Pacific have frequently been on the chopping block as among the first high-risk areas to be affected by these problems. The UN has designated 2014 as the International Year of Small Island Developing States, calling for urgent action to address the problems faced by small island societies from the combined perspective of environmental, political and economic issues. As a result, atoll societies in particular have been attracting attention as they stand out among small islands for their small size, have the highest risk of global warming and face a critical situation. Atolls are ring-shaped landforms consisting of coral reefs and sediments, of which there are about 500 in the world, particularly in the North-South Trade Wind Belt. When coral reefs and sediments rise above sea level, a bead-like chain of state islands is formed. The state islands are narrow and low-lying, with the only freshwater resources being natural water and subterranean freshwater lenses. The flora is poor in both variety and quantity, the soil is thin and the fauna is also poor. Compared to oceanic islands of volcanic origin, resources are scarce and unstable, and the environment is extremely harsh for human settlement due to its susceptibility to climatic and weather fluctuations.

　In recent years, research on atoll societies facing global warming has been conducted extensively in the world, mainly in the Pacific Ocean. In Japan, in particular, advanced research has been led across diverse disciplines, including earth and planetary sciences, geography, coastal engineering, archaeology and anthropology, to elucidate the characteristics of the natural environment and human settlement history of atolls and to propose measures to deal with the various problems caused by global warming. However, most of the research has focused on so-called "urban atolls" such as Majuro Atoll in the Republic of the Marshall Islands, Funafuti Atoll in Tuvalu, Tarawa Atoll in the Republic of Kiribati, and Rangiroa Atoll in French Polynesia. They are atoll societies that include islets with relatively large land areas, and that have undergone colonial development in modern and contemporary times, with populations concentrated in the thousands or tens of thousands, and are highly accessible by sea and air from other islands and the continent.On the other hand, less than 10% of the approximately 170 inhabited atolls in the Pacific are ‘urban atolls’, and more than 90% have a population of at most a few hundred people due to the small size of the islets and their remoteness from other islands and continents. Comprehensive studies on the natural environment, society and culture of these far-remote atolls have been scarce.