Decadal changes of biomass carbon stock in the Indo-Gangetic mangrove area: Insights from landsat remote sensing

Abstract

The anthropogenic increase in atmospheric CO₂ has created the need for precise measurement of terrestrial and coastal carbon sinks, especially in geomorphologically active intertidal environments. Mangroves, which store disproportionately high quantities of “Blue carbon” in above-ground biomass and deep alluvial sediments, are central to global carbon budgets. The Indo-Bangladesh Sundarbans, the world’s largest mangrove system, represents a critical biophysical interface where dynamics within the Ganges-Brahmaputra-Meghna delta are crucial. This study proposes a remote sensing framework that combines Python-based geospatial analytics with the computational capabilities of Google Earth Engine to quantify above-ground carbon biomass for the years 2004, 2014 and 2024. Spatiotemporal patterns are assessed in relation to geomorphological settings, estuarine hydrodynamics, and anthropogenic disturbance regimes along the deltaic gradient. The model was validated using five-fold cross-validation, demonstrating satisfactory predictive performance while quantifying the associated uncertainty. The results of this study indicate spatial heterogeneity but mainly stable carbon storage over the two decades. The mean carbon stock increases from 41.51 Mg C/ha in 2004 to 42.55 Mg C/ha in 2014, followed by a marginal increase to 43.21 Mg C/ha in 2024. The maximum biomass carbon values decreases slightly from 92.29 Mg C/ha in 2004, to 88.30 Mg C/ha in 2014 and then reach 85.17 Mg C/ha in 2024, indicating localized reduction in dense mangrove stands. Although middle regions of mangrove extent degraded, the decadal change map shows slight but persistent biomass growth (2004–2014) and partial recovery in numerous western sectors in both decades. These findings underscore the necessity for targeted restoration of hydrologically stressed zones, salinity regulation, and sediment reconnection strategies to preserve Sundarbans carbon resilience under changing climatic and anthropogenic stressors.