Spatiotemporal analysis of ground surface displacement using InSAR technique for monitoring peatland health in Sarobetsu Mire, Japan

Peatlands are a valuable environmental resource on Earth due to their large carbon storage capacity and role as a breeding ground for biodiversity. However, many of them are currently at risk of decline due to land development and climate change. We investigated the effectiveness of satellite-based Interferometric Synthetic Aperture Radar (InSAR) technique to support peatland conservation and restoration projects by monitoring the degree of peatland degradation and restoration. Sarobetsu Mire is the largest peatland in Japan, however its natural vegetation has been significantly disturbed by pasture development, drainage channels, and peat mining. We collected C-band SAR images from the Sentinel-1 satellite from 2015 to 2025. We created a series of surface displacement maps with a spatial resolution of 20 m using interferometry, Short Baseline Subset (SBAS), and phase unwrapping procedures. We then analyzed seasonal surface elevation changes during a snow-free period (207 days in total). Relative surface elevation change predicted by InSAR was highly correlated with ground observations (mean bias = -0.001 m, RMSE = 0.019 m, r = 0.58). Seasonal surface displacement clearly responded to changes in groundwater table. The amplitude of seasonal surface displacement differed significantly between natural vegetation and peat-mining ruin, and among the dominant vegetation classes (Sphagnum, Moliniopsis, and Phragmites). This differential dynamics indicates the amount and physical properties of subsurface peat deposits and potentially be a useful indicator of peatland health.