Millions of People Are at Risk of This Rare Climate Change Threat — Study

Flooding from glacial lakes is already threatening millions of lives due to climate change.

You’ve probably heard that glaciers are in big trouble due to climate change.

But glacial melt due to global warming isn’t just a problem for rising sea levels — it also poses an urgent threat to millions of people living near the icy masses. New research assesses for the first time the number of people worldwide who are at risk of flooding from glacial lakes. The findings were published Tuesday in the journal Nature.

What you should know first — As a result of climate change, melting water can pool into beds in glaciers, forming lakes. When water from these lakes overflows and is suddenly released — due to avalanches or other phenomena — they can effectively flood the surrounding area — much like a dam bursting. Scientists refer to this phenomenon as “glacial lake outburst floods” (GLOF).

“Typically, they occur when the natural dam that creates the lake fails, releasing the water in the lake downstream in a flood,” Tom Robinson, a co-author on the study and University of Canterbury researcher, tells Inverse.

Unless you live near a glacier, there’s a good chance you’ve never heard of these floods. In fact, they are pretty rare, but when they occur, they can cause significant property damage and loss of life. This occurred in the 2013 glacial lake outburst floods in Kedarnath, India.

Using an inventory of glacial lakes around the world and the Human Development Index — which factors in a country’s socioeconomic development — scientists were able to determine not only the number of people living in the path of these floods but also the regions where people were most vulnerable to them.

Pictured here: Dig Tsho in the Langmoche valley, Khumbu Himal, Nepal. An avalanche caused flooding from a glacial lake here in 1985. The High Mountain Asia region has the highest risk of glacial lake outburst floods globally.

Matthew Westoby

What the scientists found — The researchers found that 15 million people globally were vulnerable to glacial lake flooding.

While there are glacial lakes in places like Switzerland or the Pacific Northwest of the U.S., flooding from these lakes does not pose a significant threat since they’re in sparsely populated, rural areas.

“Switzerland, Iceland, and Canada have all experienced damaging [floods] in the past, but the comparatively smaller and less vulnerable exposed population means these rarely kill people here, at least in the last several decades,” Robinson says.

Instead, the researchers found people living in the high mountain areas of Asia — where these lakes are located — are at the greatest risk. Approximately one million people live within ten kilometers (six miles) of a glacial lake in this region. People who live in such close proximity to these lakes are most vulnerable because it’s difficult for them to get advance warnings of any floods.

Just four countries — Pakistan, India, China, and Peru —account for more than half of the global population at risk of glacial lake floods. China and Pakistan have the highest total populations exposed to flood risk.

Roughly 60 percent of people worldwide who are exposed to glacial lake flood risk live in the high mountain regions of Asia, such as near the Himalayas. Just four countries — Pakistan, India, China, and Peru —account for more than half of the global population at risk of glacial lake floods. China and Pakistan have the highest total populations exposed to flood risk.

Apart from Asia, people living near the Andes in South America in Bolivia and Peru are also especially vulnerable due to low human development scores like high poverty and government corruption. In other words: It’s not the size of the lakes but other factors like the number of people and socioeconomic issues that determine a region’s vulnerability to flooding.

Why it matters — Anyone who’s been paying attention to climate change knows how it has heightened the risk of severe floods around the world, like last year’s devastating flooding in Pakistan.

But when it comes to flooding from glacial lakes, specifically, researchers in the Nature study say there is a geographic gap between the academic research and the actual people living on the ground. Between 1990 and 2015, most research on glacial lakes centered on the North American Cordillera and Hindu-Kush-Karakoram mountain ranges, even though people in North America aren’t significantly at risk of glacial lake floods.

A figure from the study shows areas that are at risk of glacial lake outburst floods around the world. Peru and high mountain regions in Asia are key hotspots of flood risk.

Taylor et al

Since 2015, researchers have shifted to focusing on glacial lakes in the Himalayas — where many people are definitely at risk of glacial lake outburst floods — but less attention has been paid to the Andes mountain range. In the last seventy years, several thousand people have died due to glacial lake floods in the Cordillera Blanca — a Peruvian mountain range that is part of the larger Andes system.

The number of global glacial lakes has increased by more than fifty percent since the 1990s — and climate change is a key factor in their growth.

“As the climate continues to warm, glacier retreat will form larger and more numerous lakes,” Robinson says.

Nowhere is this more apparent than in the Andes region, where the number of glacial lakes shot up by a whopping 93 percent in the last two decades due to glacier melt. Similarly, more people in the Andes have moved closer to glacial lakes, increasing their flood risk. It’s not unlike how more Americans are moving into areas of high wildfire risk despite the ongoing climate crisis. The increase in glacial lakes makes these floods a more pressing threat as the planet heats up.

“So, lakes that perhaps aren’t a concern at present may become a concern in the future, and entirely new and potentially dangerous lakes may form,” Robinson adds.

What’s next — The researchers have honed in on a glaring oversight: We lack data on the people who are most vulnerable to glacial lake outburst flooding on a warming planet.

So the next step is to acquire more data, especially from the Andes — and fast. Without such data, it’ll be more difficult to prepare for the coming flood — literally — of climate change disasters.

“Our ongoing work now is trying to understand how that danger has changed over the last several decades and how it will continue to change in the future,” Robinson says.