Whether and when rock faces become unstable depends on various factors, including topography, rock composition, weak zones, permafrost, frost and thaw cycles, glacier retreat, heavy precipitation, vegetation and earthquakes. Climate change often plays an indirect role, making it difficult to quantify its influence precisely.

However, experts agree on the case of the Spitze Stei above Kandersteg: the warming of the Alpine permafrost is contributing to the destabilisation of the rock masses on the slope. The absence of permafrost allows more water to penetrate the rock, accelerating the movement of the rock masses. At Spitze Stei, slide speeds of up to several metres per year are being measured. The municipality of Kandersteg hopes that the 16 million cubic metres of rock will break off piece by piece and that the protective measures taken will be sufficient to prevent a disaster in the valley.

THE ROLE OF PERMAFROST

Permafrost in the Alps generally increases the strength of rock masses and thus their stability. It accounts for around 5% of Switzerland’s land area. Its condition is continuously monitored by the Swiss Permafrost Monitoring Network (PERMOS). The data shows that Alpine permafrost is warming and thawing at increasingly greater depths due to climate change.

THE BLATTEN CASE

In May 2025, an ice and rock avalanche buried the village of Blatten in the canton of Valais. Permafrost at Kleines Nesthorn played an important role here. Thanks to an excellent monitoring system, a warning was issued in good time before the event, allowing the inhabitants to be evacuated. However, the village was completely destroyed.

In the aftermath of the disaster, the discussion centres on questions such as the influence of climate change on the event and who will bear the financial consequences. Another particularly important issue is how to reliably predict catastrophic chains of events in the future. This will also determine whether areas at risk can continue to be inhabited. In addition, one question is becoming increasingly urgent: should a disaster always be followed by reconstruction?

ICE AND ROCK AVALANCHE, BIETSCHHORN / BLATTEN, Valais (2025)

On 28 May 2025, Blatten in the Lötschental valley (canton of Valais) was hit by a massive ice and rock avalanche. Following major rockfalls on the Kleines Nesthorn and a collapse of the Birch Glacier, approximately 9 million cubic metres of ice and debris crashed into the valley, burying the village of Blatten and parts of the hamlet of Ried. The village buildings were destroyed by the debris or flooded by the Lonza River, which was dammed up by the debris.

The area marked in black indicates the path of the rock, debris and ice masses. The dark blue line marks the glacier’‘s position shortly before the event. The light blue line shows the glacier’‘s position in 1938 at the time the relief was constructed by Eduard Imhof, then Professor of Cartography at ETH Zurich.

Bietschhorn relief 1:2000 (Eduard Imhof, 1938/1939);
on loan: ALPS Swiss Alpine Museum, Bern

Further information about the exhibit

The costs of climate-related disasters such as droughts, forest fires, floods, heavy rainfall, storms and mass movements are borne by insurance companies, governments, those affected and aid organisations. Low-income people in the Global South are particularly hard hit: without insurance, they have to pay for the damage themselves – often losing everything. Many of these countries also have little government funding for reconstruction.

Whether major greenhouse gas emitters should pay for climate damage is politically controversial. The link between emissions and individual disasters is difficult to prove. However, pressure is growing on wealthier countries to contribute to the costs. The Loss and Damage Fund was established in 2025 to help particularly vulnerable countries cope with the consequences of climate change.

In the long term, costs will rise for everyone: infrastructure must be made more crisis-proof, emergency plans improved and aid expanded. Insurance will also become more expensive as risks increase.

The consequences of climate change are becoming increasingly noticeable, especially for insurance companies and reinsurers. According to Munich Re, natural disasters – 93% of which are weather-related – caused damage amounting to USD 320 billion in 2024. Only around USD 140 billion of this was insured.

This insurance gap affects millions of households and businesses. When basic infrastructure such as energy plants or agricultural land is affected by extreme weather events, it can disrupt entire (global) production chains.

As weather events become more extreme, insurance costs rise, for example for storms, hail, drought or flooding. If the risks become too great, insurers and reinsurers (who cover global risks) pull out. Preventive measures can reduce risks, damage and thus costs.

One example is hail insurance in Switzerland, which has been in existence since 1880. Almost 70% of agricultural land is insured. Measures such as hail nets can reduce crop losses and premiums – a win-win for farmers and (re)insurers. By promoting such protective measures, the insurance industry is also contributing to climate change adaptation.

On 28 May 2025, Blatten in the Lötschental valley in the canton of Valais was hit by a massive ice and rock avalanche. Following major rockfalls on the Kleines Nesthorn and a glacier collapse on the Birch Glacier, around 9 million cubic metres of ice and debris broke loose, crashed into the valley and buried the village of Blatten and parts of the hamlet of Ried. The village buildings were destroyed by the debris or flooded by the Lonza River, which was dammed up by the debris.

One person lost their life, but around 300 residents were evacuated in time. The damage amounts to around 320 million Swiss francs. The municipality is planning to rebuild, but experts advise against rebuilding the village in the same location.

This is the first ice and rock avalanche in Switzerland that has been proven to have destroyed a residential area.

In Switzerland, landslides and similar events are considered natural disasters and are covered by building insurance. This is compulsory in most cantons – but not in Valais. Anyone in Blatten who was not insured has lost everything and must pay for the reconstruction themselves. According to the Swiss Insurance Association, the damage could amount to several hundred million Swiss francs – not including public infrastructure such as roads.

The municipality is already planning ‘New Blatten’. The costs are high and will only be partially covered by private insurers. The canton of Valais has pledged CHF 10 million in emergency aid, and the federal government CHF 5 million. A disaster fund is being considered. A national fundraising campaign by Swiss Solidarity has raised around CHF 21 million – including for private hardship cases. Even in well-insured Switzerland, there are gaps in insurance coverage that mostly affect less privileged sections of the population.

The Swiss Confederation‘s natural hazard agencies work closely with researchers to promote the monitoring of natural hazards in Switzerland. The planned ETH Swiss GeoLab in Lucerne will evaluate Earth observation data continuously recorded by sensors, drones and satellites. The data will be used for modelling and risk assessments in order to identify hazards at an early stage and to plan and implement protective measures.