Under continued global warming, plants in the Himalayan region is shifting to higher elevation in the mountains, a study has found.
Between 1999 and 2022, the vegetation line shifted upwards in all six regions studied — ranging from 1.42 metres per year in Khumbu, home of Mount Everest, to 6.95 metres per year in Manthang, Nepal, according to the findings published in the journal ‘Ecography’.
Researchers, led by those at the University of Exeter, UK, said that with climate warming, a reduced snow depth could be a key potential explanatory driver of the changes.
“The alpine zone is a harsh environment dominated by smaller plants and woody shrubs,” lead author Ruolin Leng, from the University of Exeter’s department of earth and environmental sciences, said. “But as the climate changes, conditions in the Himalaya are changing in various ways — from temperature shifts and changes in snow cover to the availability of water and nutrients,” Leng said.
The researchers combined satellite images with long-term climate data to assess vegetation, looking for both “greening” — signifying more vegetation or more leafy vegetation — and “browning”, which could indicate less vegetation, or more woody vegetation.
“Results revealed consistent upward shifts in vegetation lines across all regions, with rates ranging from 1.42 (metres per year) in Khumbu (Nepal) to 6.95 (metres per year) in Manthang (central High Mountain Asia). Initial levels of vegetation greenness generally increased from west to east,” the authors wrote.
Across all study regions, greening trends were found to be more prevalent compared to browning, while significant browning trends were observed in the eastern regions, specifically in Khumbu and Bhutan.
Even as the Himalayas are warming faster than the global average, a lot of the studies have focussed on the melting of snow and ice, and implications for water security for the billions depending on them, Leng said.
“Less research has focused on plants, particularly the impact of these small alpine plants living at high altitude. But plant communities can also affect the water cycle — so our findings raise important questions that must be investigated,” the lead author said.
Previous research showed that plant life is expanding across the Himalayan region, but the recent study assesses and quantifies the upward trend in more detail, the researchers said.
Author Karen Anderson, from the Environment and Sustainability Institute, University of Exeter’s Penryn Campus, added, “We tend to overlook these little plants but this is a perfect example of how small-scale processes might have impacts on important catchments, feeding rivers that supply millions of people with drinking water.”
“When you consider that we’re talking about a very extensive alpine ecosystem covering a massive area in the Himalaya, it has the potential to generate significant effects. For example, alpine plants may shade the soil, trap snow, change stores and flows of water, and therefore profoundly affect the water cycle,” Anderson said.
