On May 28, 2025, Switzerland witnessed one of its largest mass movements in recent history, as a section of Birch Glacier in Valais broke away, burying 90% of the village of Blatten under ice, rock and mud. More than 130 buildings were destroyed, with insured losses estimated in the hundreds of millions of Swiss francs.
The collapse was the result of geological instability and glacial dynamics, both increasingly influenced by climate change. Around ten days prior, rockfalls from the nearby Kleines Nesthorn mountain, likely triggered by thawing permafrost, added weight to the glacier. This additional load led to an acceleration in the glacier’s motion, reaching up to 10 meters per day. These early warning signs enabled authorities to evacuate all 300 residents before the disaster unfolded, though tragically, one local farmer working outside the designated safe zone lost his life.
Having visited Birch Glacier in 2019 on a research trip with the Department of Geography, University of Cambridge (Figure 1), I witnessed first-hand the fragile stability of the landscape. The drastic transformation since then is a reminder that risk doesn’t stand still. Under climate change, natural catastrophes like wildfires, floods, and windstorms are becoming more frequent and severe, posing growing risks to communities and businesses. The evolving climate is not only intensifying known hazards, but also introducing new and emerging risks that may fall outside traditional models and risk registers.
Credit: Prof. Ian Willis, Scott Polar Research Institute, University of Cambridge.
In the case of the Birch glacier, early signs prompted evacuation. But in many other cases, weak signals may go unnoticed or unheeded, especially when the risk isn't well understood or monitored. With this in mind, here are five glacier-related risks that illustrate the kinds of emerging climate threats businesses and communities may increasingly need to consider in a changing world.
01
The collapse in Blatten is one of the most high-profile examples of this risk, but it is far from isolated. In 2002, the Kolka Glacier avalanche in Russia buried multiple villages and led to 120 fatalities. In 2019, homes in Italy’s Aosta valley were evacuated following warnings that part of a Mont Blanc glacier was close to collapse.
Numerous glaciers worldwide are currently being monitored for similar signs of disintegration. For example, Spitze Stei in Switzerland is being closely monitored, where the volume of unstable rock is estimated to be twice that of Birch Glacier, making it a concern for future collapse.
As global temperatures rise, thawing permafrost and glacier retreat will pose an increasing threat to local communities and infrastructure, particularly in high mountain regions such as Alps, Himalayas, Andes and Alaska.
02
Glacial Lake Outburst Floods (GLOFs) are the sudden and catastrophic release of water from glacial lakes, often resulting in severe downstream flooding. These lakes typically form from meltwater pooling behind ice or moraine dams at the base or margins of glaciers. Sudden drainage can occur if the dam is weakened by melting, collapse or external triggers such as earthquakes.
The resulting flooding can cause significant damage to property and infrastructure downstream. The highest risk of GLOF impacts is in the Himalayas, with approximately 1 million individuals living within 10km of glacial lakes.[1] One of the earliest well-documented modern GLOFs in the Himalayas occurred in Nepal in 1985, when the sudden outburst of Dig Tsho glacial lake destroyed a hydropower plant, 14 bridges, and several homes.
Climate change is increasing the risk of GLOFs by accelerating ice melt and expanding the size and number of unstable glacial lakes. To help clients assess and manage this growing threat to their assets and construction projects, WTW has developed a global GLOF model (Figure 2) that estimates the current and future average annual likelihood of outburst floods.
03
Accelerating ice melt in mountain regions can also destabilise surrounding slopes, triggering rockslides or landslides into fjords that displace water and generate tsunamis.
Fjord tsunamis pose significant risks to local coastal areas. In 2015, 180 million tons of rock collapsed into the Taan Fjord in Alaska. The event generated a wave with a run-up of 193m – one of the highest instrumental tsunamis ever recorded. Recent assessments have identified similar rockfall vulnerabilities in parts of Norway and Greenland.
While still rare, the potential for sudden, high-impact waves in narrow fjords represents an emerging risk for the marine insurance sector. Had commercial or cruise ships been in the Taan Fjord at the time, liability damages could have run into the hundreds of millions of dollars.
04
On World Water Day this year, the United Nations warned that glacier melt puts two billion people at risk of food and water scarcity and threatens $4 billion of global GDP.[2]
Glacial retreat has a direct impact on hydropower, initially increasing waterflow before then causing long term declines in production and reliability. Agriculture is also at risk. Millions of farmers globally rely on glacial meltwater for irrigation and livestock. In the Himalayas alone, 129 million farmers are dependent on this water source,[3] making crop yields increasingly uncertain.
Changing water resources may also sharpen geopolitical tensions. As availability shrinks, demand could trigger conflict, shifts in regional power, and climate migration as people move to water-secure areas.
Scenario work led by Dr. Cullen Hendrix, a senior fellow at the Peterson Institute of International Economics and senior research fellow at the Center for Climate & Security, in collaboration with WTW will explore how water scarcity could exacerbate tensions between India and Pakistan—especially following India’s unilateral suspension of the Indus Waters Treaty.
05
According to the Intergovernmental Pannel on Climate Change, global mean sea levels are projected rise by between 0.43 and 0.84 meters by 2100, depending on the future greenhouse gas emission scenario considered.[4] A key driver of this rise is the melting of land-based glaciers and ice sheets.
An important impact of rising sea levels will be the increased frequency and magnitude of storm surges associated the tropical and extra-tropical cyclones. Each incoming storm surge will arrive on higher baseline sea level, and may reach further inland in some regions, threatening assets that were previously considered safe from coastal flooding.
Key coastal economic centres, such as ports, may face mounting disruption, with knock-on effects for global supply chains and economic productivity in cities like New York, Rotterdam, Shanghai, and Dhaka.
Some regions may also become unhabitable and uninsurable, with entire islands and coastal communities at risk of submersion. As a consequence, heightened geopolitical tensions between countries may arise due to the pressures of displacement and resource scarcity.
The collapse of Birch Glacier is a reminder that as the climate warms, traditional approaches to natural catastrophe risk management need to also evolve. As once-rare events become more plausible, the need for dynamic, climate-informed risk management will become increasingly important.
For local and global risk managers, the challenge is identifying, quantifying and managing the multifaceted risks that stem from these events. An effective approach involves integrating forward-looking climate scenarios with traditional risk models to explore a variety of future business scenarios. Consideration of multi-sectoral dependencies in these scenarios can add significant value — for example, exploring how increasing glacial melt concurrently affects both agriculture yields and geopolitical security.
This approach helps companies screen their entire portfolio of assets, operations and supply chains to identify current and future vulnerabilities. A deep dive of the most at-risk exposures can then guide decisions about how best to avoid, reduce and transfer risk.
