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Glaciers across the globe are rapidly thinning, with those in the Hindu Kush Himalaya (HKH) region experiencing the most dramatic losses due to climate change — retreating 65 per cent faster in 2011-2020 than in the previous decade, according to a new United Nations report released on the World Day for Glaciers.
The Asia-Pacific region is home to some of the world’s highest mountains and most extensive glacier systems — and is among the most vulnerable to climate change. Spanning five million square kilometres of high mountains, the region contains approximately 100,000 km2 of glaciers.
Often referred to as the “Third Pole” or the “Water Tower of Asia”, this region stores more ice and snow than anywhere else on Earth outside of the Arctic and Antarctic. Over ten major river systems originate here, supporting nearly two billion people.
If global temperatures rise by 1.5 degrees Celsius to 2°C, glacier volume in the HKH region could decline by 30-50 per cent by 2100. If warming exceeds 2°C, the region may lose 45 per cent of its 2020 glacier volume.
Stretching over 3,500 kilometres across eight countries — Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal and Pakistan — the HKH mountains feed ten major river basins. They are home to 240 million people, with an estimated 1.65 billion more downstream depending on their waters for drinking and sanitation, agriculture, hydropower and ecosystem services.
Globally, the outlook is equally stark. Around 1.1 billion people live in mountainous regions — two-thirds in towns and cities.
If temperatures rise between 1.5°C and 4°C, mountain glaciers worldwide are projected to lose 26 to 41 per cent of their total mass by 2100, compared to 2015 levels, stated the UN World Water Development Report 2025 released March 21, 2025. The report presented the latest scientific understanding of the role mountains and glaciers play in the global water crisis.
“Mountains worldwide, including those in the tropics and small islands, are undergoing unprecedented changes. And we all ultimately live downstream,” Michela Miletto, UNESCO WWAP Coordinator and Richard Connor, Editor-in-Chief, wrote in the report.
Heïdi Sevestre, a glaciologist with the Arctic Monitoring and Assessment Programme — a Working Group of the Arctic Council — recounted the recent demise of the Conejeras Glacier in Colombia in just a month. In August 2023, the glacier was still visible, covered in snow.
“This [the visibility] is always a great sign for tropical glaciers or glaciers in general to continue receiving snow. But a month later, a video captured by a mountain guide showed the glacier had completely vanished,” she stated.
Such losses are accompanied by unprecedented changes. Warming and melting trends are altering hydrological systems. In the Third Pole region, studies project increased total runoff, particularly in monsoon-dominated basins. However, impacts vary by river basin. While glaciers are critical to freshwater supplies, the contribution of glaciers, snow and ice differs depending on time and location.
Glacier melt can lead to natural disasters. It contributes to Glacial Lake Outburst Floods (GLOF) — sudden, destructive floods caused by glacier-fed lakes — as well as flash floods and landslides, threatening human settlements, agriculture, infrastructure and energy systems. Since the 1990s, the number and area of glacial lakes have increased substantially. GLOFs have claimed over 12,000 lives in the past 200 years.
In the HKH region alone, GLOFs may have caused over 7,000 fatalities in the last 190 years. The risk of such disasters is expected to triple by the century’s end. “Many consequences will go beyond the limits of adaptation,” warned the report.
The report also highlighted the paradox of how mountain-based industries contribute to — and are simultaneously affected by — climate change. For example, lithium mining in the Plurinational State of Bolivia and northern Argentina and Chile involves significant water extraction, placing immense stress on local communities.
Producing one tonne of lithium requires around 2,000 cubic metres of water. The report also raised concerns about hydropower-fuelled cryptocurrency mining in mountainous areas, particularly in Central Asia.
Hydropower is one of the dominant industries in mountain regions. Yet unregulated and poorly planned development of small hydropower plants is straining water resources. In Georgia, for instance, some rivers have dried up due to excessive hydropower infrastructure.
“Mountain communities and their leaders also tend to have limited human and financial resources to resist such developments,” read the report.
Meanwhile, climate change is directly affecting hydropower generation through melting glaciers, shifting precipitation patterns and increased evaporation. Despite this, there is a lack of global data on how much current and planned hydropower depends on glacier melt.
There is also no conclusive evidence that global warming will increase water availability for hydropower — any temporary boost from glacial melt could be offset by greater evaporation. Satellites are already recording a decline in global lake water storage, including artificial reservoirs.
Water governance in mountain regions is significantly weaker than in lowland areas, the report stressed. In the HKH, effective transboundary cooperation is lacking, with mutual distrust posing a key barrier to data sharing.
“Data- and information-sharing are crucial steps for transboundary disaster risk reduction, such as for GLOFs and river floods. Mistrust between riparians limits benefit-sharing in water and its related services like irrigation, energy and navigation,” read the report.
The report spelled out six transboundary actions for the HKH region. First, cooperation at all levels for sustainable and mutual benefits. Second, recognise and prioritise the uniqueness of the people. Third, take concerted climate action at all levels to keep global warming to 1.5°C by 2100.
Fourth, take accelerated actions to achieve the Sustainable Development Goals and nine mountain priorities. Five, enhance ecosystem resilience, halt biodiversity loss and land degradation. Six, engage in regional data- and information-sharing, and science and knowledge cooperation.
The report also recommended incentives for communities protecting watershed areas crucial for hydropower, drinking water and tourism, through payments for ecosystem services.
Finally, it highlighted the urgent need for increased funding and support for mountain communities. “While substantial funding is potentially available for investment in sustainable development in mountain regions, access to major support programmes has been relatively limited,” it added.