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Greening in the Alps is visible from space

A new study led by the University of Lausanne and the University of Basel has found that global warming has a significant impact on the Alpine region. Just like the Arctic, this European mountain range is becoming greener, with satellite data showing evidence that vegetation above the tree line has increased in nearly 80 percent of the Alps. Moreover, the experts have also detected decreases in snow cover in 10 percent of the area.

By using high-resolution satellite data from 1984 to 2021, the scientists discovered that, over this period, the plant biomass above the tree line increased in more than 77 percent of the observed regions – a phenomenon of “greening” caused by climate change that is already well documented in the Arctic.

“The scale of the change has turned out to be absolutely massive in the Alps,” said study lead author Sabine Rumpf, an assistant professor of Ecology at the University of Basel.

According to Professor Rumpf and her colleagues, the Alps are becoming greener because an increasing number of plants are colonizing new areas, and the vegetation is becoming denser and taller due to changes in precipitation and rising temperatures. Yet, although Alpine plants are well-adapted to harsh conditions, they are not very competitive, and may soon lose their evolutionary advantage. “The unique biodiversity of the Alps is therefore under considerable pressure,” Professor Rumpf warned.

In contrast to such massive changes in vegetation, the extent of snow cover above the tree line has not changed so radically since 1984. Although significant decreases in snow cover have only been found in about 10 percent of the Alps, the researchers consider it a worrying trend.

“Previous analyses of satellite data hadn’t identified any such trend,” explained study senior author Antoine Guisan, an ecologist at the University of Lausanne. “This may be because the resolution of the satellite images was insufficient or because the periods considered were too short.”      

“For years, local ground-based measurements have shown a decrease in snow depth at low elevations,” added study co-author Grégoire Mariéthoz, an expert in Earth Surface Dynamics at the same university. “This decrease has already caused some areas to become largely snow-free.”

According to the scientists, as global warming continues, the Alps will turn increasingly greener, creating a vicious circle.  

“Greener mountains reflect less sunlight and therefore lead to further warming – and, in turn, to further shrinkage of reflective snow cover,” explained Professor Rumpf. In addition, rising temperatures will cause further melting of glaciers and thawing of permafrost, which can lead to landslides, mudflows, and rockfalls. Finally, snow melting will have a significant impact on drinking water supplies, as well as on tourism and recreation activities.

The study is published in the journal Science.

By Andrei Ionescu, Staff Writer

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