High mountains: anticipating cascading risks

As a result of global warming, glaciers, mountain slopes, and mountain streams have become more unstable, leading to unprecedented chains of disasters

Landslides, rockfalls, flash floods… communities living in high-mountain regions face numerous natural hazards. But in recent years, climate change has significantly altered the frequency and scale of these hazards, triggering a cascade of events that are increasingly difficult to predict. In the face of these new risks, scientists are calling for a rethinking of our forecasting frameworks.

Climate change is destabilizing high-altitude mountain regions

In May 2025, in the Lötschental valley in Switzerland, a series of high-mountain rockfalls triggered one of the most spectacular Alpine disasters ever recorded. Several million tons of rock broke away from a mountain peak and accumulated on the Birch Glacier below. Already weakened by several years of global warming, the glacier becomes highly unstable and collapses in turn a few days later. The enormous mass of ice and debris thus released blocks the course of a river, causes a lake to form upstream, and buries a large part of the village of Blatten, which the authorities had fortunately evacuated beforehand.
Of a magnitude rarely observed, this event demonstrates how phenomena that were once contained can now trigger major disasters.

With climate change, we are witnessing events of unprecedented scale, as well as interactions between phenomena that we have never observed before, simply because we have never lived in the climate we have today. “We are facing disasters that are profoundly unexpected, both in scale and in nature,” explains Kristen Cook, a geomorphology researcher at IRD within the ISTerre unit.

Rethinking Land Use Planning in the Himalayan Regions

This situation calls for new frameworks for planning in environments profoundly altered by climate change. This issue is particularly acute in the Hindu Kush-Himalaya (HKH) region, a vast mountain range spanning eight countries, home to some of the world’s highest peaks as well as immense freshwater reserves.

This region, which is particularly vulnerable to natural hazards, is currently the focus of major development projects: hydroelectric dams, roads, tunnels, tourist complexes, and new urban centers. As a result, risks in the region have increased significantly. In this rapidly changing region, scientists are calling for risks to be integrated into infrastructure design from the very beginning.

We believe that development in the HKH region is necessary, but it cannot proceed without incorporating risk assessment and mitigation from the planning stage onward. Infrastructure projects require a rigorous risk analysis before any design or investment decisions are made. “Many hydropower plants are at risk of GLOFs, as recent events have already shown,” says Pema Gyamtsho, an agronomist and Director General of ICIMOD (International Centre for Integrated Mountain Development) in Kathmandu.

In this context, international organizations specializing in disaster management, such as ICIMOD (International Centre for Integrated Mountain Development), have revised their recommendations to governments in order to incorporate recent scientific advances and develop new frameworks for action based on a multi-hazard and proactive approach.

Residents at the heart of the warning systems

Another key point raised by scientists is the involvement of local communities in management and warning systems. The difference in human cost between events such as those in Blatten and Melamchi highlights the importance of systems capable of rapidly evacuating populations.

Researchers emphasize the need to co-develop these systems with the affected residents. Training plays a key role: knowing the warning signs, evacuation routes, and proper response protocols significantly improves responsiveness. In many regions, the flow of information between villages when an unusual event is observed already serves as an initial form of warning that should be strengthened and formalized.

These participatory systems are relatively simple and inexpensive to implement, but above all highly effective. Residents possess valuable knowledge that complements the most advanced scientific tools.

“Countries with comprehensive multi-hazard early warning systems have six times lower disaster-related mortality rates, making community engagement a proven and quantifiable priority in saving lives,” concludes Pema Gyamtsho.

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Reference

Xuanmei Fan, Kushanav Bhuyan, Xin Wang, Kristen L. Cook, Ugur Ozturk, Simon Loew, Pema Gyamtsho, John D. Jansen & Qiang Xu, Rethinking policy on high mountain cascading hazards, Nature Geoscience, novembre 2025. DOI : 10.1038/s41561-025-01834-w

This article was initially published Arthur Hunaut for IRD le Mag’.

Updated on 15 June 2026