According to a study on satellite data is growingon the slopes of Mount Everestand the surrounding mountains more plants than 25 years ago.
The increased plant growth could have a larger impact, particularly on the flow of water into rivers flowing down from the Himalayas, says Karen Anderson of the University of Exeter, UK. “When the ecology changes, it impacts hydrology. But no one has thought about that yet.”
Anderson's team used data from NASA's Landsat satellites to study high-altitude vegetation in the Himalayas between 1993 and 2018. They focused on the subnival zone, the highest of the regions above the tree line with seasonal but not permanent snow cover. The plants in this zone are mostly small grasses, shrubs and mosses.
The mountains in the Himalayas are becoming greener
The researchers found that the subnival zone in the Himalayas is vast, with an area at least five times the area covered by permanent ice and snow. “There is hardly any ecological data from this region,” says Anderson.
By tracking which regions appeared green in satellite images, the team found that sublevel vegetation has increased since 1993. The greatest increase occurred between 5000 and 5500 meters above sea level.
It is not clear why the plants settle at higher altitudes. “My initial guess is that the temperature limit will be lifted,” says Anderson. The Himalayas are warming particularly quickly due to human greenhouse gas emissions, so altitudes that were once too cold for plants may now be tolerable. Studies suggest that plants move uphill for this reason. Anderson says the extra carbon dioxide in the air could also help plants grow.
The consequences
Most studies on the effects of warming on the Himalayas have focused on melting glaciers, which could devastate the water supplies of neighboring countries like India through floods and droughts. Anderson says it's important to find out how the new plants affect water flow. They can absorb more heat than bare ground, causing greater warming and therefore faster snow melting - or they can absorb moisture and reduce water flow.
It is unclear how much higher the plants could grow if the climate continues to warm. Some hardy plants have already been found to grow at 6,159 meters above sea level. However, the highest mountain peaks are still very cold, covered in snow and ice, and lack soil. “Whether or not plants could grow on the summit of Everest, I think that’s unlikely in our lifetime or even the next 100 years,” Anderson says.
Those:Global Change Biology
