From the article: As many as 15 million people live in areas that could be flooded by a natural dam failing at a glacial lake, according to the first global analysis of the hazard.

Tom Robinson at the University of Canterbury in New Zealand and his colleagues identified glacial lakes in satellite imagery. They then determined the number of people living within 50 kilometres of each lake, and within 1 kilometre of the river where water would flow in the event of a glacial lake outburst flood (GLOF). These floods can happen when an ice or rock dam holding back a glacial lake fails, or a rock slide sends water sloshing over a natural dam.

The researchers found up to 15 million people could be affected, with 9 million in the Himalayas, 2.5 million in the Andes and 2.2 million in the Alps. More than half of the 15 million live in either India, Pakistan, Peru or China.

Outburst floods are unlikely at many glacial lakes, and the study presents a simplified view of the areas any flooding would affect, says Simon Allen at the University of Zurich in Switzerland, but he says the global view helps draw attention to vulnerable and understudied regions.