Bhutan has lost 27 glaciers and nearly 10 percent of its total glacier area over the past nine years, according to the newly released Bhutan Glacier Inventory (BGI) 2026, raising fresh concerns about the accelerating impacts of climate change on the country’s fragile mountain ecosystems.
The inventory, released by the National Centre for Hydrology and Meteorology (NCHM), shows that Bhutan now has 673 glaciers covering 571.86 square kilometres, down from 700 glaciers covering 629.55 square kilometres recorded in the previous national inventory. The findings represent a 9.16 percent reduction in glacier area, amounting to a total loss of 57.69 square kilometres between 2016 and 2025.
Most glacier-fed river basins recorded declines in both glacier numbers and glacier area, underscoring the continued retreat of glaciers across the Bhutanese Himalayas. Researchers, however, observed an increase in glacier numbers within the Mangde Chhu sub-basin, explaining that the rise resulted from larger glaciers fragmenting into smaller ice bodies rather than the formation of new glaciers.
The Pho Chhu sub-basin remains the country’s most glacier-rich region, containing 200 glaciers with a combined area of 232.49 square kilometres, while the Punatsang Chhu basin continues to hold the largest share of Bhutan’s overall glacier coverage.
NCHM Director General Karma Dupchu said Bhutan’s glaciers remain among the country’s most valuable natural assets.
“The glaciers of Bhutan are among the country’s most important natural assets, serving as vital freshwater reserves and providing essential ecosystem services that sustain downstream communities, agriculture, hydropower generation, and biodiversity,” he said.
He noted that glaciers are highly sensitive indicators of climate change, making continuous monitoring essential for understanding environmental change and supporting evidence-based planning and decision-making.
The Director General said the updated inventory marks a significant milestone in Bhutan’s glacier monitoring programme through the adoption of advanced technologies.
“The adoption of Machine Learning and Deep Learning technologies reflects NCHM’s commitment to embracing innovative scientific methods and keeping pace with the rapidly evolving field of cryospheric research,” he said.
According to the report, the inventory was produced using Sentinel-1 radar and Sentinel-2 optical satellite imagery collected during the post-monsoon season of 2025. Scientists combined the satellite data with deep learning models—specifically DeepLabv3+ with a ResNet101 backbone—to automatically delineate glacier boundaries before conducting detailed manual verification to enhance accuracy.
The report states that the integration of artificial intelligence has significantly improved the efficiency, consistency and reliability of glacier mapping, particularly in rugged mountain terrain and debris-covered glacier areas.
The inventory also found that the majority of Bhutan’s glacier ice remains concentrated between 5,000 and 5,700 metres above sea level. Researchers estimated the uncertainty in glacier mapping at just 0.374 percent, indicating a very high level of confidence in the results.
Karma Dupchu said the updated inventory will serve as an important scientific resource for future planning and climate action.
“This updated inventory will serve as an important reference for researchers, planners, policymakers and development partners working on climate change, water resources, hydrology and mountain hazards,” he said.
He added that the publication provides an updated national benchmark against which future glacier changes can be measured, strengthening understanding of climate change impacts on Bhutan’s mountain ecosystems.
The Director General also acknowledged the contributions of the Cryosphere Services Division and collaborating institutions involved in preparing the inventory.
“I would like to commend the dedication and hard work of the Cryosphere Services Division team and all collaborating institutions and experts who contributed to the development of this inventory,” he said. “Their efforts have strengthened Bhutan’s capacity to monitor and understand its cryosphere and reaffirmed our commitment to advancing scientific knowledge for the benefit of present and future generations.”
The Bhutan Glacier Inventory 2026 is the country’s third national glacier assessment and builds on the Bhutan Glacier Inventory 2018, the first nationally led glacier inventory prepared by NCHM.
The 2018 study documented 700 glaciers covering approximately 630 square kilometres, establishing Bhutan’s first comprehensive national database on glacier distribution and characteristics.
The latest inventory introduces artificial intelligence, machine learning and deep learning into glacier mapping, marking a major technological advancement over previous assessments.
According to NCHM, the updated database will strengthen long-term glacier monitoring, climate change research, water resource management and efforts to reduce the risks of glacial lake outburst floods (GLOFs). As Bhutan’s glaciers continue to retreat under a warming climate, the inventory is expected to guide future policy decisions, enhance climate resilience and support more effective disaster preparedness.
Sherab Dorji, Thimphu
