Climate change is threatening the world's mountain regions

On July 3, the pinnacle of the Marmolada glacier in Italy's Dolomites broke loose, releasing a landslide that overwhelmed dozens of hikers and killed seven. "We heard a loud noise," an eyewitness told the Ansa news agency. "We saw an avalanche of snow and ice heading towards the valley at high speed, and we knew something bad had happened." An intense heat wave had gripped Italy since late June.

The world's mountains are rugged, but delicate. They have a huge impact on even distant lowlands but are highly sensitive to climate change. Temperatures are rising significantly faster in mountain areas, well outpacing other habitats. As a result, snow and glaciers are disappearing with consequences for water systems, biodiversity, natural disasters, agriculture and tourism.

The Intergovernmental Panel on Climate Change says lower elevation snow cover could fall by as much as 80% if emissions continue unabated. Glaciers, too, are retreating, with a similar melt expected in the European Alps at current levels of CO2 output. At least a quarter of the world's permafrost is in high mountain areas. As permafrost thaws, it will release vast amounts of greenhouse gases.

The changing climate has a deep impact on water systems, but the effects change over time. Initially, glacier-fed river systems rise in flow with accelerated melting. But in areas with much-reduced glacier cover, such as Peru's Cordillera Huayhuash mountain range, rivers weaken due to less seasonal melt. Many areas with smaller glaciers have already hit that turning point.

Climate change has altered the make-up of wildlife in mountain areas. Some flora and fauna, including lowland bird species, are winners, as more areas open up for them to thrive. But this comes at a cost to species adapted to the cold, such as snowshoe hares in North America and snow leopards in Central and South Asia, which have to move higher up the mountains to survive.

Retreating glaciers and thawing permafrost make mountain slopes less stable, leading to more frequent rockfalls, landslides and flooding. Wildfires are on the rise, particularly in the western US, where snow is melting sooner. And melting glaciers will also release heavy metals, such as mercury, and other legacy contaminants.

Almost 10% of the world's population lives in high mountain regions. But life there is becoming more marginal with worsening economic opportunities and a higher risk of natural disasters. The aesthetic, spiritual and cultural aspects of mountain landscapes are impacted, too. The Indigenous Manangi community in Nepal, for example, sees the loss of glaciers as a threat to their ethnic identity.

As temperatures rise, mountain farming and tourism take an economic hit. Equally, high-altitude infrastructure — such as roads, railways, pipelines and buildings — suffer as the foundations on which it was built destabilize. In some areas, thawing glaciers have revealed mining opportunities, but taking advantage of this can cause other problems, like pollution.

Less snow and thawing permafrost have hurt the skiing, glacier tourism and mountaineering sectors. In Bolivia, which has lost half its glaciers over the last 50 years, the world's highest ski resort is a sad display of rusted ski lifts. Ski resorts are now relying on artificial snow at great environmental cost, while others are pivoting to alternative sports to account for shorter seasons.

As glaciers shrink, ultimately reducing the amount of water that flows down to rivers and valleys, local farmers are facing lower agricultural yields. This is combined with reduced access to electricity as hydropower operations suffer. In Nepal, farmers are dealing with drying soils, making it harder to grow potatoes and fodder. But others are switching to new crops suitable for warmer climes.