Violent flooding from glacial lakes formed or widened by climate change threatens at least 15 million people worldwide, estimates a study published Tuesday in NatureCommunications.
Four countries are particularly at risk: India, Pakistan, China and Peru, note the researchers who carried out this first global assessment of the areas threatened by this phenomenon.
The volume of lakes formed when glaciers disintegrate around the world due to global warming has jumped 50% in 30 years, according to a previous 2020 study based on satellite data.
These lakes are particularly unstable because they are most often dammed by ice or sediments composed of loose rocks and debris. When accumulated water bursts through these natural barriers, massive floods can occur downstream, causing thousands of deaths in their path.
“It is not the areas with the greatest number of glacial lakes or those whose swelling is the fastest that are necessarily the most at risk. The danger comes rather from the number of people near said lakes and their ability to face a flood or not, ”explains the main author of the study, Caroline Taylor, doctoral student at the University of Newcastle in England.
Thus, thousands of people have been killed by floods caused by the overflow of glacial lakes in high mountain Asia, but only a handful in the Pacific Northwest located in North America, even though this region has twice that number. more.
According to the study, some 90 million people in 30 countries live in 1,089 glacial lake basins and 15 million of them reside within one kilometer of a flood path.
In the high Asian mountain area alone, more than nine million people are in direct line of potential flooding from glacial lakes, including five million in northern India and Pakistan.
The latter country, which has more than 7,000 glaciers in the spectacular Himalayan mountain ranges, experienced devastating floods last summer, which affected more than 33 million people.
Recent research has shown that half of Earth’s 215,000 glaciers and a quarter of their mass will melt by the end of the century, even if global warming can be capped at 1.5°C, the ambitious goal of the Paris agreement that many scientists now consider out of reach.
Over the past century, a third of global sea level rise has come from melting glaciers.