Geospatial Change Detection of Mangrove Loss, Persistence, and Regeneration in Lombok Island, Indonesia (2019-2024) Using Geomatic Technologies

This study quantitatively analyzed the spatial-temporal dynamics of mangroves on Lombok Island, Indonesia, by integrating Landsat 8 OLI imagery with GIS-based analysis for the years 2019 and 2024. The study area spans 4,738.14 square kilometers along Lombok Island's coast (center point: 116°19′ 29.7984″E; 8°39′3.5244″S). Landsat 8 scenes (20/11/2019 and 19/02/2024; 30 m) were preprocessed with radiometric correction (DN to reflectance) and atmospheric correction using Dark Object Subtraction (DOS), followed by band compositing (Bands 2–7) and cropping. Land-cover mapping was carried out using a supervised Maximum Likelihood Classifier (MLC) with Regions of Interest (ROIs) supported by high-resolution basemaps, and change detection was obtained through overlay analysis to identify persistence, loss, and regeneration. The extent of mangrove forests decreased from 1,570.27 hectares (ha) in 2019 to 1,439.94 ha in 2024, representing a net reduction of 130.33 ha (–8.3%). Transition mapping identified 1,059.34 ha of persistent mangroves, 511.13 ha converted from mangrove to non-mangrove, and 386.22 ha of regeneration (non-mangrove → mangrove), enabling the identification of priority zones for targeted conservation and restoration. Classification reliability was confirmed through an independent confusion-matrix-based accuracy assessment (N = 171 points/year), yielding Overall Accuracy (OA) of 95.91% (κ = 0.92) in 2019 and 95.32% (κ = 0.91) in 2024. A limitation is the lack of field-based ground-truth validation.