Land cover changes and driving factors in highland peatlands of Humbang Hasundutan, Indonesia, based on multi-temporal remote sensing

Highland peatlands are increasingly subjected to land-use pressures that threaten their ecological functions and carbon storage capacity. This study analyzed land-cover change, vegetation dynamics, and peatland-related carbon emissions in Humbang Hasundutan Regency, North Sumatra, Indonesia, using multi-temporal Landsat imagery (2014, 2019, and 2023), vegetation indices (NDVI and GNDVI), and GIS-based spatial analysis supported by field validation. The results revealed substantial peatland transformation, characterized by an increase in cultivated land from 2,906 ha (47.0%) in 2014 to 4,364 ha (70.6%) in 2023, while natural forest declined from 1,642 ha to 244 ha, representing an 85.1% reduction. Built-up land expanded from 115 ha to 1,351 ha, reflecting increasing infrastructure and settlement development. Land-cover transition analysis indicated that the largest conversions involved open land and natural forest being transformed into cultivation areas. Vegetation index analysis showed that cultivated peatlands were predominantly associated with moderate vegetation density (NDVI and GNDVI values of 0.6–0.8), whereas the remaining natural forests exhibited values exceeding 0.8, indicating dense canopy cover. Estimated net greenhouse gas emissions reached 48,609 tCO₂e yr⁻¹, with biomass loss from deforestation contributing approximately 86% of total emissions. The land-cover classification achieved high reliability, with an overall Kappa coefficient of 95%. These findings demonstrate a rapid transition from natural peatland ecosystems toward intensive land use, resulting in ecological degradation, reduced forest cover, and increased carbon emissions. This study contributes to the limited body of knowledge on tropical highland peatlands and highlights the importance of sustainable land-use planning, peatland conservation, and continuous monitoring to support long-term ecosystem resilience.