Shrubs and grasses are springing up around Mount Everest and across the Himalayas, one of the most rapidly heating regions of the planet.
The impact on water supplies of the small but significant increase in vegetation between the treeline and snowline is not yet known but could increase flooding in the vast Hindu Kush Himalayan region, which covers 4.2msq km(1.6m sq miles), feeds Asia’s 10 largest river systems and supplies 1.4 billion people with water.
Scientists used satellite data to identify increases in vegetation in the inaccessible subnival (the highest zone allowing plant growth) ecosystem, made up of grasses and dwarf shrubs with seasonal snow. This ecosystem is known but could play a crucial role in the region’s hydrology, covering between five and 15 times the area of permanent glaciers and snow in the region.
Studying images from 1993 to 2018 provided by NASA's Landsat satellites, researchers from Exeter University measured the spread of vegetation cover across four height brackets from 4,150 to 6,000 metres above sea level.
The melting of Himalayan glaciers has doubled since the turn of the century, with more than a quarter of all ice lost over the last four decades. Research has suggested that its ecosystems are highly vulnerable to climate-induced shifts in vegetation.
“A lot of research has been done on ice melting in the Himalayan region, including a study that showed how the rate of ice loss doubled between 2000 and 2016,” said Dr Karen Anderson, of the Environment and Sustainability Institute on Exeter’s Penryn Campus in Cornwall.
“It’s important to monitor and understand ice loss in major mountain systems, but subnival ecosystems cover a much larger area than permanent snow and ice, and we know very little about them and how they moderate water supply.”