Mapping water dynamics in Borneo’s biodiversity hotspot: a satellite-based analysis

Water availability is a critical global concern affected by climate and anthropogenic change. Water needs of natural habitats are often neglected in water management assessments especially in areas where natural and man-made systems compete for essential resources. This study examines variations in water availability and hydrological drought occurrences over the past two decades (2002–2021) in Borneo, a region facing rapid deforestation and climate change. Owing to its high endemism and increasing habitat loss, Borneo hosts 2 out of the 238 biodiversity hotspots of the world. Utilizing Gravity Recovery and Climate Experiment (GRACE) satellite datasets from the Jet Propulsion Laboratory (JPL) and Goddard Space Flight Centre (GSFC), we assess changes in Equivalent Water Thickness (EWT) and hydrological droughts using the Standardized Terrestrial Water Storage Index (STI) and Water Sustainability Index (WSI). Our findings reveal decreasing water storage (10 cm/year) during 2003–2010 period followed by some improvement in recent years (2010–2021), particularly notable in zones with greater deviation from the mean anomaly of up to 15 cm/ year (Zone B, C & D). Spatially, northern regions exhibit positive trends in water storage (10–15 cm/year). WSI results indicate higher sustainability in the southern coastal area (Zone A: 0.55). STI analysis reveals severely dry conditions over 12-month scale, with more areas affected in the Northern parts than in South. These findings highlight the complex interplay of climate change, land use, and water management practices. Our work calls attention to the critical importance of sustainable water resource management in biodiversity hotspots like Borneo.