The Japanese government is stepping up efforts to preserve its remote border islands using advanced laser surveying technology. The initiative, aimed at safeguarding Japan’s exclusive economic zone (EEZ) and territorial waters, involves detailed topographical analysis to detect erosion and other natural changes that threaten island stability.
Beginning this fiscal year, the Cabinet Office and the Geospatial Information Authority of Japan will collaborate on laser-based surveys and aerial photography across 473 of Japan’s designated remote border islands. A new automated topographical matching system will be developed by fiscal 2026 to compare laser data over time and flag early signs of island degradation.
Remote islands serve as crucial reference points for defining Japan’s maritime boundaries. Under international law, a country’s territorial waters extend about 22 kilometers (12 nautical miles) from its coastline, while its EEZ can stretch up to 370 kilometers (200 nautical miles). These zones are vital for securing access to fishing grounds, mineral resources, and strategic navigation routes.
Traditionally, border islands were monitored every 10 years using aerial and satellite photography, supported by occasional on-site inspections. However, the slow pace made it difficult to detect and respond to erosion in time. In contrast, the new system will utilize laser scanning from helicopters—a technique that bounces light off land surfaces to generate precise digital models of terrain.
About 25 erosion-prone islands, including Kita-Kojima, Naka-Kojima, and Minami-Kojima in the Hizen-Torishima group (Nagasaki Prefecture), will receive intensive monitoring every five years. These islands, located in the East China Sea, are part of a region rich in fishery resources and geopolitical significance.
The urgency of the initiative follows the 2018 submersion of Esanbe-Hanakita-Kojima Island in Hokkaido due to erosion and drifting ice. In 2023, government records showed a net loss of 11 islands, with 14 disappearing and only three new islands identified. Such losses directly impact the size of Japan’s EEZ and threaten its economic and territorial claims.
Officials hope the new system will enable early detection and timely intervention, such as the seawall construction already underway at Okinotorishima Island—the southernmost point in Japan.
“Losing these islands would reduce Japan’s territorial waters and EEZ, potentially weakening our maritime interests,” a Cabinet Office official emphasized.
