The devastating effects of climate change will render South Asia — home to a fifth of the world’s population — uninhabitable in the next century, a new study suggests.

The grim future comes in the form of deadly heat waves, which researchers expect to start hitting India, Pakistan and Bangladesh, within “as little as a few decades.”

The region is home to about 1.5 billion people. Areas such as the Indus and Ganges river basins, which produce much of the region’s food, will also be affected.

The study, published in the journal Science Advances, utilized detailed computer simulations using top-notch global circulation models to show areas vulnerable to epic changes in climate caused by carbon emissions.

The researchers from The Hong Kong University of Science and Technology, Loyola Marymount University and Massachusetts Institute of Technology also based their analysis on a recent study that showed the combination of high temperature and high humidity — an index measured by a reading called wet-bulb temperature — as most fatal for humans in hot weather.

Wet-bulb temperatures above 35°C (95 degrees Fahrenheit) prevent the body from cooling itself (by sweating), making it unable to survive in just a few hours.

The study found that about 75% of the South Asian population — Bangladesh, India, Nepal, Pakistan and Sri Lanka — will experience wet-bulb temperatures of at least 31°C (87.8 degrees Fahrenheit) by 2100, while an unfortunate 4% will face the survivability limit of 35°C.



However, fatal heat waves have already been occurring in South Asia. In 2015, around 3,500 people died in one of the hottest waves recorded in India and Pakistan.

A recent study also found that increasing temperatures in India were responsible for the suicides of roughly 60,000 farmers in the last 30 years.

For now, the researchers are calling for measures to dodge the ghastly future. Study co-author Elfatih Eltahir from MIT said in a press release:

“There is value in mitigation, as far as public health and reducing heat waves. With mitigation, we hope we will be able to avoid these severe projections. This is not something that is unavoidable.”