Madrid. Satellite data has shown that global warming has a particularly pronounced impact on the alpine region, which is becoming greener.
Researchers from the universities of Lausanne and Basel in Switzerland found that vegetation above the tree line has increased in almost 80 percent of the Alps and snow cover is also decreasing, although only slightly so far, according to published in the magazine Science.
The melting of glaciers has become a symbol of climate change in the Alps. The reduction in snow cover is already visible from space, but it is by no means the biggest change, concludes a research team led by Sabine Rumpf of the University of Basel and Grégoire Mariéthoz and Antoine Guisan of the University of Lausanne.
In collaboration with colleagues from the Netherlands and Finland, the experts studied snow cover and vegetation change using high-resolution satellite data from 1984 to 2021. During this period, plant biomass above the tree line increased by more than 77 percent of the observed area. This phenomenon of “greening” due to climate change is already well documented in the Arctic and is beginning to be detected in the mountains as well.
“The scale of change has turned out to be massive in the Alps,” Rumpf, lead author of the study and, since February, an adjunct professor at the University of Basel, said in a statement. The Alps are getting greener as plants colonize new areas and the vegetation is generally denser and taller.
Previous studies have focused on the influence of global warming on alpine biodiversity and changes in the distribution of plant species. Until now, however, no one had carried out such a comprehensive analysis of changes in vegetation productivity in the Alps.
The authors show that the increase in plant biomass is mainly due to changes in rainfall and the lengthening of vegetation periods as a result of rising temperatures.
“Alpine plants are adapted to harsh conditions, but they are not very competitive,” Rumpf says. As environmental conditions change these specialized species lose their edge and are outcompeted and the unique biodiversity of the Alps is therefore under considerable pressure.”
In contrast to vegetation, the extent of snow cover above the tree line has changed only slightly since 1984. For their analysis, the researchers excluded regions below 1,700 meters, glaciers, and forests.
In the rest of the regions, they found that the snow cover had decreased significantly in almost 10 percent of the area. This may not sound like much, but the researchers are keen to stress that it is nonetheless a worrying trend.
“Previous analyzes of the satellite data had not identified any such trends. This may be due to the fact that the resolution of the satellite images was insufficient or that the periods considered were too short”, explains Guisan.
“For years, local ground measurements have shown a decrease in snow depth in low-lying areas. This reduction has already caused some areas to be practically without snow”, adds Mariéthoz. From the satellite data, it is possible to distinguish whether a particular area is covered with snow or not, but it does not allow conclusions to be drawn about the depth of the snow.
As global warming continues, the Alps will increasingly turn from white to green, creating a vicious cycle. “Greener mountains reflect less sunlight and therefore cause more warming and, in turn, more reduction in reflective snow cover,” says Rumpf.
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