On March 21, 2025, the UN
released the annual World Water Development Report. In alignment with
the designation of 2025 as the International Year of Glaciers’
Preservation and the 2022 resolution of the UN General Assembly on
sustainable mountain development, this report draws worldwide attention
to the importance of mountain waters, including alpine glaciers, in the
sustainable development of mountain regions and the downstream societies
that depend upon them, in the context of the rapidly changing mountain
cryosphere.
For billions of people, mountain meltwater is
essential for drinking water and sanitation, food and energy security,
and the integrity of the environment. But today, as the world warms,
glaciers are melting faster than ever, making the water cycle more
unpredictable and extreme. And because of glacial retreat, floods,
droughts, landslides and sea-level rise are intensifying, with
devastating consequences for people and nature.
This report
offers solutions to help us simultaneously mitigate and adapt to rapid
changes in our frozen water resources. It provides a clear overview of
the current state of play and recommends what needs to change. The
urgent need to drastically reduce carbon emissions is emphatically
repeated. By detailing the connections between mountain fresh water,
essential services and the natural world, this publication highlights
the critical importance of conserving the cryosphere to the achievement
of the SDGs.
Status of the world’s water resources
- According
to the most recent global estimates (from 2021), the agriculture sector
dominates freshwater withdrawals (72%), followed by industry (15%) and
domestic (or municipal) use (13%). Sector-specific freshwater
withdrawals vary considerably as a function of a country’s level of
economic development. Higher-income countries use more water for
industry, whereas lower-income countries use 90% (or more) of their
water for agricultural irrigation. - Over
the period 2000–2021, global freshwater withdrawals increased by 14%,
corresponding to an average growth rate of 0.7% per year. Most of this
increase occurred in cities, countries and regions undergoing rapid
economic development. - Population
growth does not appear to play a highly significant role in increasing
demand for water. In fact, countries where per capita water use is the
lowest, including several countries in Sub-Saharan Africa, are often
those with the fastest growing populations. - Twenty-five
countries (including India), which account for one-quarter of the
world’s population, face ‘extremely high’ water stress every year. - Approximately 4 billion people, or half the world’s population, experience severe water scarcity for at least part of the year.
- Climate
change is increasing seasonal variability in, and uncertainty about,
water availability in most regions. Pollution, land and ecosystem
degradation, and natural hazards can further compromise the availability
of water resources.
Progress towards Sustainable Development Goal 6
Sustainable Development Goal (SDG) 6 seeks to ensure the availability and sustainable
management of water and sanitation for all. Progress towards all SDG 6
targets is off track – some severely. For example, an estimated 2.2
billion people (27% of the global population) were without access to
safely managed drinking water in 2022, with four out of five people
living in rural areas lacking even basic drinking water services.
Mountain regions
- As the ‘water towers’ of the world, mountains are an essential source of fresh water.
- They are vital for meeting basic human needs such as water supply and sanitation.
- These
waters are also vital in ensuring food and energy security to billions
of people living in and around mountain regions and in areas downstream. - The
main economic activities in mountain regions are agriculture,
pastoralism, forestry, tourism, mining, cross-border trade and energy
production. Mountain regions provide high-value products such as
medicinal plants, timber and other forest products, unique mountain
livestock and speciality agriculture products. - They
are global hotspots of agrobiodiversity, with a large fraction of the
world’s gene pools for agriculture and medicinal plants preserved in
mountains. - Mountains
feature a diverse range of ecological zones, each resulting from a
specific combination of factors such as elevation, geomorphology,
isolation and microclimatic conditions (e.g. insolation). Consequently,
they often have higher endemic biodiversity than lowlands, including
important genetic varieties of agricultural crops and animals. - They also have an equally diverse range of human cultures.
Glaciers and the mountain cryosphere
- The
mountain cryosphere is one of the most-sensitive components of the
Earth system to global climate change. Mountains generally supply more
surface runoff per unit area than lowlands, due to higher precipitation
and lower evaporation. - Alpine glaciers also store and release water, albeit over much longer time-frames.
- In many high mountain regions, the formation of seasonal snow cover provides most of the freshwater storage.
- Most of the world’s glaciers, including those in mountains, are melting at an
increasing
rate. However, snow-melt accounts for a greater volume of streamflow in
most river basins with a cryosphere component, and is often
substantially higher than glacier melt. - Global
warming is accelerating glacier melt, decreasing snow cover, increasing
permafrost thaw, and prompting more extreme rainfall events and natural
hazards. - Water flows from mountains will become more erratic, uncertain and variable.
- Changes
in the timing and volume of peak and low flow periods, increased
erosion and sediment loads will affect water resources downstream, in
terms of quantity, timing and quality. - Dust,
combustion-related soot deposits including black carbon, and microbial
and algal growth on snow and glacier surfaces are becoming more common
due to increased frequency and/or intensity of dust storms, air
pollution and wildfires. They can accelerate melt rates by decreasing surface albedo until the next snowfall. - The consequences of climate change, including higher temperatures, glacial recession,
permafrost thaw and changing precipitation patterns, can affect flood
and landslide risks. The processes associated with these risks, such as
debris flows and floods, avalanches, rock- and icefalls, landslide dam
outburst floods and glacial lake outburst floods (GLOFs), can pose
significant threats to communities, wildlife and infrastructure.
Food and agriculture
Agriculture and pastoralism are essential sources of livelihoods for people in rural
mountain areas. One in two rural mountain dwellers in developing
countries are vulnerable to food insecurity. Remoteness and
inaccessibility, as well as land degradation (which leads to poor
quality soils) and large variations in seasonal water supply, combine to
create significant challenges for mountain agriculture.
Mountain
communities preserve many of the rarest crop varieties and medicinal
plants. They have developed valuable traditional knowledge and
techniques in crop cultivation, livestock production and water
harvesting that help to sustain entire ecosystems.
Indigenous Peoples in mountains have unique and valuable local knowledge, traditions
and cultural practices that contribute to sustainable food systems,
land management and biodiversity preservation. Terrace farming can be
adapted to local slope conditions. Its numerous benefits include
reducing surface water runoff, promoting water conservation, reducing
soil erosion, stabilizing slopes, enhancing habitat and biodiversity
production, and sustaining cultural heritage.
Responses to climate-driven impacts in mountains vary significantly in terms of goals and priorities, speed of implementation, governance and modes of decision-making, and the extent of financial and other resources to implement them.
Adaptation
responses commonly include changing farming practices, infrastructure
development including for water storage, application of Indigenous
knowledge, community-based capacity-building and ecosystem-based
adaptation (EbA).
Human settlements and disaster risk reduction
Roughly
1.1 billion people live in mountain regions, two-thirds of whom live in
towns and cities. The remoteness of mountain communities, difficult
terrain and heightened exposure to natural hazards often lead to higher
costs for transport, infrastructure, goods and services. These also pose
particular challenges for the financing, development and maintenance of
water supply and sanitation systems, drainage networks and other
essential water infrastructure.
Rapid
and unplanned urbanization in mountain regions is also placing pressure
on fragile mountain ecosystems, affecting water availability, quality
and security.
Decentralized water and sanitation systems can be
particularly effective in mountain regions, reducing the risk of
infrastructure damage in rugged terrain subject to frequent landslides.
Natural
hazards such as landslides, earthquakes, floods, GLOFs and avalanches
can damage the water supply and sanitation infrastructure, and disrupt
access to water, sanitation and hygiene services. Such hazards increase
the vulnerability of already vulnerable and often marginalized mountain
communities, and destabilize some of their wealth-generating sectors,
including agriculture, tourism and biodiversity.
Examples
of adaptation actions in mountain regions include: feasibility studies
for building emergency storage and bypasses and controlled releases from
glacial lakes; river basin management and planning for basin
optimization; monitoring temporal changes in glaciers; and establishing
GLOF risk reduction and early warning systems in glaciated river basins.
Industry and energy
Water-dependent
industries have developed in mountain areas where water and other
resources are found in relative abundance. In addition to industrial and
energy production, water is also required to process minerals, produce
timber and develop tourism in mountain areas.
Hydropower generation is one of the main industries in mountain areas. The presence
of a slope and the shape of mountain valleys make it possible to
generate hydropower without building large dams and reservoirs. However,
the construction and presence of dams and reservoirs, transmission
lines and substations can have a significant negative impact on fragile
mountain ecosystems.
Beyond
water availability, a significant challenge for industry and energy is
the elevation at which it is possible to operate. As such conditions can
generate huge investment and running costs, industrial activities are
typically limited to those with high returns on investment.
Industrial and energy development can affect water quality. Remote
mountain areas can be difficult to regulate, resulting in uncontrolled water
withdrawals and discharges, including pollutants.
Responses are available and are being developed to make industry and
energy production in mountain areas more sustainable. The circular
economy promotes water-use reduction, recycling of used water and
reuse of water resources. Environmentally sound technologies encompass
practices such as the use of less-polluting technologies, better resource
management and efficient waste recycling. The greening of grey
infrastructure or its replacement with green infrastructure can be particularly effective in mountain areas.
Environment
Mountain and highland ecosystems provide essential ecosystem services to people living in mountains, and to billions in connected lowland areas. Water regulation (including water storage and flood regulation) is one of the most important services.
Other key ecosystem services include reducing the risk of erosion and
landslides, cooling local temperatures, carbon sequestration, providing food and fibres, and maintaining pools of genetic resources for locally adapted crops and livestock.
Forests cover an estimated 40% of mountain areas, performing a protective function against natural hazards by stabilizing steep slopes, regulating flows to groundwater, reducing surface runoff and soil erosion, and mitigating the potential for landslides and floods. Unsustainable tree cultivation can lead to increased soil erosion and reduced soil water infiltration.
Mountain soils develop under harsh climatic conditions. They differ
significantly from lowland soils, as they are shallower and more vulnerable to erosion. Such soils are easily and often degraded by various human activities, especially removal of vegetation that exposes the bare soil. The recovery of degraded soils and thus ecosystems at high elevations is slow.
At the ecosystem level, most of the options for addressing the impacts
of changes in the cryosphere and high mountains involve conserving or
restoring ecosystem functionality to maintain or enhance ecosystem
services at local to regional scales through nature-based solutions (NbS)
or EbA. These approaches are now commonly seen as an adaptation
component in the nationally determined contributions of many mountain
countries around the world.