The view from above shows: Over the course of decades, more and more plants have spread above the tree line in the Alps. This endangers the alpine flora, which specializes in high altitudes.
According to a study, the Alps are becoming greener and greener due to climate change. The vegetation has increased above the tree line in almost 80 percent of the Alps, researchers from the Universities of Lausanne and Basel write in the journal Science.
As the evaluation of satellite images from the years 1984 to 2021 also showed, the area of snow cover decreased at the same time – albeit only slightly so far.
“The extent of the change in the Alps turned out to be absolutely massive,” says Sabine Rumpf from the University of Basel. Plants colonized new areas and vegetation generally became denser and taller. The increase in plant biomass is due to changes in precipitation and longer growing seasons as a result of rising temperatures.
This effect could threaten the special alpine flora. “Alpine plants are adapted to harsh conditions, but not very competitive,” says Rumpf. As environmental conditions changed, these specialized species would lose their advantage and be displaced. “The unique biodiversity of the Alps is therefore under considerable pressure,” explains the researcher.
In contrast to the vegetation, the snow cover above the tree line has changed only slightly since 1984, according to the study. The respective snow depth could not be determined exactly from the satellite images, it said. In any case, with global warming, the Alps would turn from white to green more and more.
“Greener mountains reflect less sunlight and therefore lead to further warming – and thus to a further shrinkage of the reflective snow cover,” explains Rumpf. Higher temperatures have caused glaciers to melt and permafrost to thaw, which could trigger more landslides, rockfalls and debris flows.