When glaciers melt due to global warming, the water collects in ever larger glacial lakes. Even tiny disturbances can then cause the natural boundaries of these lakes to break and the masses of water to spill into lower-lying areas. A study has now raised the risk of such glacial lake eruptions. According to this, around 15 million people worldwide are at risk – above all in the high mountains of Asia and the Andes, but also in the Alps, for example.
Due to climate change, the world's glaciers are retreating more and more. The meltwater forms large lakes, which in many cases are only held back by unstable natural barriers of ice or rock. If such a barrier breaks - for example because the ice melts seasonally or the ever-increasing water pressure bursts the stone barrier - a Glacial Lake Outburst Flood (GLOF) occurs. The water of the lake pours into lower-lying areas, dragging stones and chunks of ice with it, often killing many people and causing major damage to buildings, infrastructure and agricultural land.
Risk particularly high in India, Pakistan, Peru and China
Due to climate change, the number of glacial lakes has increased rapidly since 1990. The number of people living near such lakes has also increased significantly. A team led by Caroline Taylor from Newcastle University in Great Britain has now determined how high the risk of glacial lake flash floods is worldwide. The team included 1,089 glacial lake basins worldwide in the analysis and also recorded the number of people living within a radius of 50 kilometers as well as the level of development and other societal indicators of how well potentially affected regions could react to a glacial lake eruption.
The result: "Our study shows that 15 million people worldwide are at risk of possible glacial lake eruptions," the authors report. Populations most at risk are in the high mountains of Asia, which includes the Tibetan Plateau from Kyrgyzstan to China. One million people alone live within a ten-kilometer radius of a glacial lake, and 9.3 million people would be at risk from an eruption, five million of them in India and Pakistan alone. The authors highlight the Andes as a particularly critical region. "According to our results, the Asian highlands have the highest risk for the consequences of glacial lake eruptions," they write. "But the Andes are almost as high a risk and have hardly been researched with regard to this issue." According to the analysis, around two million people in the Andean region are at risk, especially in Peru and Bolivia.
Dealing with the disaster determines risk
In the Alps, too, the research team came up with a total of around one million people at risk in Italy, Switzerland, France and Austria. Due to the high level of development in these countries, however, Taylor and her colleagues come to the conclusion that social vulnerability to glacial lake eruptions is comparatively low here. "The main factors that determine the potential hazard of a GLOF event are the number of people, their proximity to a glacial lake, and most importantly, their ability to cope with flooding," explains Taylor. In contrast, the number of lakes or the speed at which the lakes grow play a less important role.
“By understanding which areas are most at risk from glacial flooding, we can take more targeted and effective risk management actions, which in turn will help minimize the loss of life and damage to infrastructure downstream from this significant natural hazard,” says Taylors Colleague Rachel Carr. Possible measures to reduce the risk include strengthening natural dams with concrete, for example, or creating drainage channels that drain the lake water in a controlled manner, making a dam rupture less likely. Early warning systems can also help to evacuate the endangered population in good time.
Source: Caroline Taylor (Newcastle University, UK) et al., Nature Communications, doi: 10.1038/s41467-023-36033-x