Unraveling the spatiotemporal dynamics of paddy rice cultivation using Sentinel-1 synthetic aperture radar imagery: a case study of Guangdong province, China

Paddy rice is the primary staple food for nearly half of the global population, highlighting the critical need to monitor its cultivation dynamics for food security. However, research on monitoring paddy rice cultivation and analyzing the driving forces behind its spatiotemporal dynamics at a large spatial scale remains limited. To address this gap, we employed Sentinel-1 synthetic aperture radar imagery and a random forest classifier to map paddy rice fields in Guangdong province, China, for the years 2016 and 2022. In addition, factors influencing the spatial distribution and temporal dynamics of these fields were analyzed using a random forest algorithm on natural geographic and socio-economic datasets. In 2022, paddy rice cultivation in Guangdong covered 9359.64 km2, as calculated from the obtained paddy rice map, which achieved a detection accuracy of 89.67%. The paddy rice fields were mainly concentrated in the southern coastal plains and the basins of the northern mountainous regions. Compared with 2016, there was a 9.55% reduction in paddy rice fields by 2022. The Paddy Rice Variation Intensity Index (PRVII) we developed revealed that this decline was primarily concentrated in key cultivation areas, with significant decreases in Zhanjiang and Meizhou (PRVII<−2.50‰). Conversely, expansion occurred in eastern Guangdong, and some stability was observed in certain Pearl River Delta cities. We identified the mean altitude and particle size of clay as key factors determining the spatial distribution of paddy rice fields, with substantial increase in the mean squared error values of 69.27% and 75.63%, respectively. Temporal changes in paddy rice fields were significantly influenced by climate factors, particularly variations in annual rainfall and average yearly temperature. Moreover, government-led policies, such as rural revitalization initiatives, played a positive role in protecting paddy rice fields from urban encroachment. These results can contribute to the understanding of the spatiotemporal dynamics of paddy rice cultivation and further inform crop management and agricultural policy decisions.