Glacial lakes: 15 million people threatened – Knowledge

In May 2022, Pakistan suffered from severe heat. Nearly 50 degrees were reached in Islamabad. But the high temperatures not only strained the bodies of the city dwellers, the consequences could also be felt high in the mountains – albeit in a completely different way: In the Hunza Valley in northern Pakistan, a fall occurred glacier to slide because a film of water had formed between its underside and the rock. The glacier tongue pushed itself into a glacial lake with force. This swelled for several weeks until it erupted and released its masses of water into the river Schyok. When it swept through Hassanabad in northern Pakistan, it not only destroyed houses and power plants, but also brought down a stone bridge – cutting off the most important transport route to China.

Glacial lakes have repeatedly erupted in different provinces of Pakistan. Because as a result of global warming When mountain glaciers around the world melt, more such bodies of water form and they swell. Since 1990, their number, area and volume have each increased by around 50 percent. This also increases the risk of outbreaks. Exactly how this happens depends on the terrain: rockfalls, avalanches or landslides can trigger waves and cause a glacial lake to burst. But sometimes it is enough for the ice in the glacier to gradually melt.

The danger is greatest in Pakistan and China. One comes to this conclusion study in Nature Communications. The scientists from Great Britain and New Zealand assess for the first time the global risk for more than 1000 meltwater lakes. They have examined both where people are particularly exposed to this potential danger and where they are particularly vulnerable. In all, 15 million people live 50 kilometers or closer to glacial lakes, the authors write. However, these people are distributed very unevenly across the world: Half are concentrated in just four countries: India, Pakistan, Peru and China.

In Pakistan, more than two million people live in a danger zone. At the same time, they are also the most vulnerable. China, on the other hand, has more glacial lakes, so the overall risk is similar to that in Pakistan. The authors point out that the number of glacial lakes does not have to be synonymous with a high level of danger. Of all the countries examined, Greenland has by far the most glacial lakes; but the danger there is zero – because nobody lives close enough to the glacial lakes.

Much more important is how exposed the population is. And here’s a worrying trend: People are moving to higher and higher altitudes. “And in doing so, they are exposing themselves to an ever-increasing risk,” says the geographer Marcus Nusser from the University of Heidelberg, who has been studying meltwater lakes in India and Pakistan for years.

Education and economic development also determine the risk

The population in this region is increasing rapidly, forcing people to farm further up in the mountains. Factors such as the illiteracy rate or income also play a role, write the authors of the Nature Communications Study. “Some people just don’t realize there’s a risk,” says Rachel Carr, a geographer at Newcastle University and a co-author of the study. “Others know about it, but have no other choice.”

In Pakistan and India together around five million people are at risk from meltwater lakes – around a third of the world’s endangered population.

The authors were surprised at how strongly the risk to people’s lives and property depends on the development of the respective regions and countries. “The focus of research so far has been primarily on the physical conditions of the lakes,” says Carr. Much more important, however, are political, economic and social factors.

In other words, the less developed a society is, the more vulnerable it is. When the illiteracy rate is high, many people cannot read information about the danger or an evacuation plan. If the government is corrupt, it may be more likely to build in flood plains and be less effective with evacuations.

While Europe did well here, the authors give Pakistan or the Andes region, for example, poor marks. All of this also explains why “only” just under 400 people have died in the European Alps as a result of the eruption of glacial lakes in the past 1000 years, but several thousand have died in the Cordillera Blanca in the northern Andes of Peru alone – and that in the past 70 years .