Jerónimo López, geologist and Himalayan climber: “The retreat of glaciers due to warming makes the high mountains increasingly unstable”

The frequency of geological disasters like the one that happened in Nepal, causing hundreds of victims, possibly thousands, is increasing as climate changes take a toll on complex and increasingly populated places like the Himalayan mountain range. Geologist and mountaineer Jerónimo López witnessed this just a year ago when he traveled to an area near the now-collapsed one, 50 years after participating in the first Spanish ascent of an ‘eight-thousander’, the Manaslu.

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The name of the documentary (available on RTVE) he premiered in spring about that trip seems prophetic: Himalaya +50. Changes in the highest mountains in the world. Recognized worldwide as an authority on polar regions—he chaired the prestigious Antarctic scientific committee SCAR, which coordinates all research on that continent—he has seen with his own eyes on numerous expeditions the impacts of climate change on the highest peaks on Earth.

Were you surprised by the tragedy that occurred in Nepal?

I was surprised by the magnitude and, above all, saddened because it is a catastrophe of unusual magnitude. Such natural phenomena have always occurred in the Himalayas because it is a seismic zone. You can see it when walking through its uneven terrain, its deep valleys. But here the origin is different. In 2025 I just returned to the place of the expedition we did in 1975, in a valley parallel to the now devastated one. We wanted to climb Larkya Peak (6,249 meters), but it was not possible because the mountain has crumbled due to climate change and there was a high risk of rockfall. We traveled through the Budhi Gandaki river valley, which also flows into the same Trishuli river of the current flood, and I was able to document the danger of landslides, of that mud and those sediments that the water now carries and that will still reach villages located further downstream.

They warn that this risk continues. Are these high mountains becoming increasingly fragile?

Of course it continues. There has been a sudden glacier break like none seen in decades, but new floods cannot be ruled out because all the slopes are destabilized at the valley bottoms. There could be another collapse causing another damming that could break again. Regarding fragility, earthquakes are frequent in the Himalayas, a young mountain range in geological terms. On a Catalan expedition to Everest in 1988, we had a very strong earthquake at base camp that caused a large avalanche on the upper part of the summit that reached us. It was a big scare. But recently, the obvious retreat of glaciers due to global warming, which causes heat waves even above 6,000 meters where the ice is, contributes to making those glaciers much more unstable. As they melt, water penetrates cracks and reaches their base, lubricating contact with the rock and increasing landslides. Also, the water from glacier retreat feeds the lakes at the head of the valleys, as I saw last year. With more water, the dams formed by moraines sometimes break. Added to this is that the permafrost, the ice in the ground, is melting more and more, leaving the terrain unsafe. As a result, the mountains are becoming more dangerous and unstable and there are more accidents. Erosion and natural dynamics on those vertical slopes do not stop and have accelerated due to climate impacts.

Is it possible to warn in advance of this type of glacier movement? Are there geological risk maps?

It is impossible in a 2,500-kilometer mountain range. Last year the collapse of the Birch glacier in the Swiss Alps also buried a village under a mass of ice, rocks, and mud, but its 300 inhabitants had been evacuated because it was monitored. There were instrumentation systems that anticipated the arrival of that flow of ‘liquid concrete’ that sweeps away any obstacle with its tremendous destructive force. But in the Himalayas, there are hundreds of rivers flowing down from Tibet, where the great rivers of India originate whose course heads south. It is an unmanageable dimension.

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And how has human presence changed in recent decades?

Before there were few people because access was very complicated, but roads and bridges have been built. What used to take days now takes hours. There are no large populations, but the current roads and bridges did not exist 50 years ago because tourism had not developed. That is why there has been that terrible number of victims. In any case, this shows that we live on a dynamic planet and that there are forces coming from inside the Earth, earthquakes, and others from outside, like the climate. Now humans are affecting the latter and, moreover, we have overpopulated dangerous areas. We are exposing ourselves to phenomena beyond our control capabilities. This summer also in the Alps there were unusual temperatures above 4,500 meters, with a rockfall wave in the MontBlanc massif, and in spring the Cordillera Blanca in Peru was closed for two months due to avalanche risk.

If early warning systems are almost impossible in that mountain range, what can be done?

More prevention and land management, learning that building in dangerous areas near rivers is not possible. It is true that events of this magnitude are exceptional, but it is important not to place buildings or other obstacles in inappropriate places. If construction happens because of more tourism, it must be done with experts, which does not prevent an earthquake or landslide from destroying everything, but it would avoid damage. On the other hand, climate change has been announced for three decades. It was known that in the 21st century we would reach extreme temperatures in the Mediterranean, that there would be accelerated sea level rises. All serious scientific work points to the need for prevention because climate is something that does not change overnight, but they also insist on mitigating the emissions that cause it. Humans are responsible for that warming.

Will what happened affect a country that lives off tourism?

I don’t think so, just as the tremendous earthquakes did not. In 2015 there were two that destroyed much of Kathmandu and it recovered. These are very attractive places, with many draws, not only for expeditions to the great peaks but also for hiking. The important thing is that they take coherent measures to increase safety, especially in certain valleys. That requires investment in a very poor country that needs international aid to advance in that area. The Himalayas depend on several countries with very different capacities and different policies. Bhutan restricts access, for example. Ultimately, it is not just about money coming from mass tourism, but about regulating these issues.

Will such violent events happen again?

Yes, especially in areas with steep slopes where sudden breaks can reach lakes and rivers whose banks are inhabited. And there are thousands of glaciers, rivers, and villages. In this case, it happened in an area very attractive for Buddhist and Hindu pilgrimage, where people go to the sacred mountain Kailash. In those high mountains crowned by glaciers, the flow of an avalanche sometimes descends thousands of meters of elevation, at speeds over 200 kilometers per hour. The growth of tourism and accommodations in these areas increases exposure to danger if there is no proper planning.

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