Scientists are issuing fresh warnings about the rate at which Peru’s glaciers are retreating due to global warming.

According to government studies, Peruvian glaciers have shrunk by 40 percent in the past four decades and the melt-off has spawned hundreds of new, small, high-altitude lakes.

Glaciologists have installed thermal sensors to monitor glacier temperatures, in addition to measuring devices used to calculate glacier retreat.

“In the past 40 years, around 996 new lakes have appeared and this is easy to understand – when a glacier recedes, the first thing it leaves behind is a basin or a cup,” says glaciologist Nelson Santillana.

In 1970, more than 20,000 people were killed after an earthquake sent a glacier sliding into the highland town of Yungay.

Measures are now in place to prevent such tragedies. Monitoring stations equipped with surveillance cameras have been set up to warn of potential glacier-related natural disasters.

Students learn about evacuation routes in school and take part in avalanche and landslide evacuation drills.

“We mustn’t forget that we have tropical mountain glaciers, so our ice masses are located on surfaces that have almost vertical slopes. As a result, they are very susceptible to spilling over, they detach into the lakes that the glacier itself has formed – this destroys the lake which violently overflows and threatens to wipe out cities and infrastructure,” says Santillana.

Peru’s 2,679 glaciers are the source of the vast majority of the country’s drinking water.

Although glacial melt-off could boost supplies in some watersheds in the short-term, the fear is that, in the long term, it will diminish fresh water supplies in this fast-growing country.