Climate change alters natural hazards in the Alps

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• Rockfalls have increased in the high Alpine region in recent decades, according to a new study.
• According to the study, the number of heavy precipitation events that can trigger mudslides has also increased significantly.
• There is more activity above the tree line and in previously unaffected areas.
• The Swiss-led team reviewed 335 studies and evaluated almost a third of them.

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When avalanches thunder down into the valley or huge amounts of rock break off, scientists have long warned that such events are likely to become more frequent as a result of climate change. To verify this, a Swiss-led team has reviewed 335 studies and evaluated just under a third of them. The results are mixed.

The experts from the Institute for Snow and Avalanche Research (SLF) in Davos examined rockfalls, landslides, debris flows and ice and snow avalanches. Their conclusion is clear in only one case: rockfall has increased at high Alpine altitudes.

"It is also clear from the literature reviewed that quantifying the effects of climate change on such mass movements remains difficult," says the study, which was published in the journal "Earth-Science Reviews". This is partly due to the complex natural system with many influences and a lack of data.

If the ground thaws, moisture can loosen rocks

Scree and rocks suddenly break off and smaller chunks tumble down a slope or rock face. Such events have increased in high alpine regions, according to the specialist article. One of the reasons: Glaciers are receding, the permafrost, the frozen ground, is thawing. Moisture in the ground can loosen stones and boulders.

As recently as the beginning of October, an estimated 10,000 cubic meters of rock broke off the Gross Tschingelhorn in Graubünden. In 2017, four million cubic meters of rock fell from Piz Cengalo. Eight hikers were killed. However, according to the scientists, there is still a lack of data on the increasing frequency.

Forces of nature in the mountains

Debris flow, landslide or landslide? They are all devastating

A debris flow, on the other hand, occurs when debris, rubble and soil slide down a steep slope due to heavy rain. Only half of the studies suggest that there are more debris flows than in the past. However, there are indications that more debris flows occur above the tree line and in areas that were not previously affected.

The studies also show that avalanches have more wet snow than powder snow. Due to the lack of snow, there are fewer avalanches at lower altitudes, but slightly more at higher altitudes.

Climate change is clearly noticeable in the Alps: the air temperature has risen by 0.3 to 0.4 degrees every decade from 1968 to 2017, as the authors quote from analyses. The amount of snow has fallen by up to 15 percent, and Swiss glaciers have lost around 43 percent of their ice volume since the 1980s until 2016, and another ten percent in 2022 and 2023.