Increased melting of glaciers and snow in the Himalayas and Tibetan Plateau threatens the food security of millions of people in Asia, a study shows, with Pakistan likely to be among the nations hardest hit.

A team of scientists in Holland studied the impacts of climate change on five major Asian rivers on which about 1.4 billion people, roughly a fifth of humanity, depend for water to drink and to irrigate crops.

The rivers are the Indus, which flows through Tibet and Pakistan, the Brahmaputra, which carves its way through Tibet, northeast India and Bangladesh, India’s Ganges and the Yangtze and Yellow rivers in China.

Studies in the past have assumed that a warmer world will accelerate the melting of glaciers and snow in the Himalayas and Tibetan Plateau, which act like water towers, the study published in the latest issue of the journal Science says.