Satellite images taken across 25 years have revealed a "significant" expansion of plant life across parts the Himalayan mountain range.
A study by scientists from the University of Exeter compared NASA satellite data from 1993 and 2018 to measure the coverage of Himalayan plants above the treeline but below the snowline - often grasses and small shrubs.
And on Mt Everest, the most famous of the Himalayan peaks, vegetation was found "at the limit" of where plants were previously thought to be able to grow.
But she said more work was needed to see what impact the increase in vegetation would have on the mountains and, more importantly, the rivers that flow from them.
"We don't know what impact changing subnival (plants growing 4,150-6,000 metres above sea level) vegetation will have on this aspect of the water cycle," she said.
"This region - known as 'Asia's water towers' - feeds the ten largest rivers in Asia."
Is climate change to blame?
The Himalayas - translated from the Sanscrit for 'abode of the snow' - has the largest concentration of glaciers on Earth, outside the polar caps.
Dr Anderson says the vegetation increase "could be caused by some climatic changes, particularly those mountain areas becoming warmer," but says "we don't have the data at present to provide solid attribution to one factor or another".
Changes in land use, changes in precipitation and snow cover, and landslides could all have contributed to the change, she says.
What's at stake?
It feeds the Indus, Ganges, Brahmaputra, Yangtze and Yellow rivers, and stretches across eight countries - from Afghanistan in the west to Myanmar in the east.
Interruptions to the water supply of these rivers - such as melting snow and ice - could threaten food security to people in these regions.