High-resolution annual cultivated paddy field maps in Japan and factor investigation for the observed declining trend using Sentinel-2 monthly composites
Japan has been facing continuous decline in cultivated paddy fields attributed mainly to the changes in dietary policy and aging population. The advent of large-scale satellite missions and remote sensing technology now enables us to analyze spatial and temporal changes in rice cultivation at both regional and local scales. Consequently, remote sensing technology empowers us to conduct in-depth examinations of areas that have undergone notable declines in production. By doing so, we can explore the primary factors behind this decline and strive to identify the root causes responsible for the observed trend. Leveraging this technology, our research (1) introduces a simple automated mapping methodology using monthly composite Sentinel-2 images, multi-level land cover/land-use masking, and paddy field differentiation thresholding using index inversion flooding signal, and (2) explores and discusses spatio-temporal variations in key local areas in the country during the recent years. To validate the mapping methodology, we compared it against government survey statistics at both regional and prefectural levels, during the years when statistics are available (2019 to 2021). The proposed approach outperformed previous mapping efforts across all prefectures of Japan, highlighting its effectiveness in improving mapping precision. The observed temporal changes in paddy field extent provide insights into the consistent reduction of paddy field density in the country. Additionally, delays in farming activities were observed in specific years and locations, likely caused by local flooding and/or insufficient water supply for irrigation and land preparation.
各種検索
サポート
ヘルプ