Context: The ‘United Nations World Water Development Report 2025 – Mountains and glaciers: Water towers’ was released to mark the first-ever World Day for Glaciers on March 21.
Relevance of the Topic: Mains: Impact of global warming on mountain ecosystems and its consequences.
United Nations World Water Development Report (WWDR)
- WWDR is a global report that provides a comprehensive assessment of the world’s freshwater resources.
- It is produced annually by the UNESCO World Water Assessment Programme, and published by UNESCO.
Major Highlights of the UNESCO’s Report
1. Glacial Melting:
- Glaciers are disappearing faster than ever. Since 1975, glaciers (which do not include the Greenland and Antarctica ice sheets) have lost >9,000 billion tonnes of mass. 450 gigatons of mass was lost in 2024 alone.
- Reasons for accelerating glacier melting:
- Warmer temperatures
- More frequent and intense wildfires
- Dust storms lead to more deposition of black carbon and other particulate matter on glacier surfaces, leading to greater absorption of solar radiation (decreased Albedo).
2. Accelerating Permafrost Thaw: In high-altitude regions, permafrost is any ground that stays frozen — 0 degrees Celsius or lower — for at least two years straight. Rising temperatures are melting permafrost in these regions rapidly.
3. Decline in Snow Cover: Reduction in snow cover in nearly all mountain regions, especially in spring and summer. Snow cover is the total of all the snow and ice on the ground. It includes new snow and previous snow and ice that have not melted. Earlier, a 2024 study found a 7.79% decline in global snow cover between 1979-2022.
4. Erratic Snowfall Patterns: Due to atmospheric warming, the rain-snow transition zone is shifting upwards, i.e., mountain ranges are receiving a greater fraction of precipitation falling as rain rather than snow. Snow duration has reduced, snow-melt is taking place earlier than usual.
Implications of the Changing Climatic Patterns:
- Consequences of permafrost thawing:
- Release of organic carbon into the atmosphere, exacerbating climate change. Permafrost contains a vast amount of organic carbon (4.5% of the global soil organic carbon) and other nutrients.
- Mountain slopes become more vulnerable to erosion, increasing the risk of landslides and other hazards.
- Consequences of increased glacial melting:
- Increased glacial lake formation and higher risk of glacial lake outburst floods (GLOFs).
- Rise in the sea level: Melted glacier ice contributes 25-30% of global sea-level rise. Between 2006 and 2016, the global mass loss of glacier ice amounted to 335 billion tonnes of lost ice per year, which corresponded to an increase in sea levels of almost 1 mm per year.
- Shorter snow duration: affects ecosystems, water supply, and agriculture. Earlier snowmelt means water is available too early in the season, causing shortages later.