The Sundarbans, the world's largest contiguous mangrove ecosystem straddling India and Bangladesh, faces unprecedented biodiversity loss driven by climate change, anthropogenic pressures, and inadequate governance frameworks. This article critically examines the multidimensional drivers, ecological consequences, and conservation implications of biodiversity decline in the Indian Sundarbans of West Bengal. Drawing on recent empirical studies, remote sensing analyses, and ecological assessments, we document accelerating habitat degradation, species population declines, and disruption of critical ecosystem services. Our analysis reveals that sea-level rise, increasing cyclone intensity, salinity intrusion, and unsustainable resource extraction are synergistically eroding the ecological integrity of this UNESCO World Heritage Site. We propose an integrated conservation framework emphasizing community-based management, climate-adaptive strategies, and transboundary cooperation. The findings underscore the urgent need for evidence-based policy interventions to safeguard this irreplaceable ecosystem and the livelihoods of approximately 4.5 million people who depend upon it.