Mangrove land cover and coastline changes in Indramayu Regency in 1991 – 2021

The Indramayu Regency, located on the northern coast of West Java, has experienced mangrove loss and dynamic shoreline changes, largely due to the conversion of mangrove areas into aquaculture ponds. This study quantifies the changes in mangrove cover and shoreline position from 1991 to 2021 and assesses their relationship. Landsat imagery for 1991, 2001, 2011, and 2021 was classified in Google Earth Engine using a Random Forest algorithm, whereas shoreline change rates were derived in ArcGIS with the Digital Shoreline Analysis System (DSAS). Total mangrove extent declined from 1,443.74 to 833.07 ha between 1991 and 2001 (−610.67 ha) with an average shoreline retreat of −15.98 m/year. From 2001 to 2011, mangroves increased slightly to 844.24 ha (+11.17 ha) as the shoreline advanced at 13.69 m/year, and from 2011 to 2021, mangrove cover expanded to 1,521.27 ha (+677.03 ha), while the mean shoreline change reverted to retreat at −1.49 m/year. Linearity tests and the low coefficient of determination (R² = 0.191) indicated that there was no significant linear relationship between mangrove change and shoreline dynamics, suggesting that effective erosion mitigation requires an integrated coastal management approach that combines mangrove rehabilitation, coastal protection, and sediment management.