The impact of global warming on the Alps is visible from space, with snow-white mountains increasingly colonized by green plants, according to a study of high-resolution satellite data.
Vegetation above the tree line in the Alps has increased by 77% since 1984, the study said. While retreating glaciers symbolize the rate of global warming in the Alpine region, researchers describe the increase in plant biomass as an “absolutely massive” change.
Rising temperatures and increased rainfall extend the growing season as plants colonize new areas and become denser and taller. Snow cover is declining, and scientists said the loss of less than 10% of the snow cover above the tree line is still significant.
“The scale of the change has turned out to be absolutely huge in the Alps,” said Prof. Sabine Rumpf of the University of Basel and lead author of the paper.
Mountainous areas are warming about twice as fast as the world average. And while greening the Alps can increase carbon sequestration, this is likely to be overcome by negative consequences, including thawing of permafrost, reduced albedo effect – less snow reflecting sunlight – and loss of habitat.
According to Rumpf, more plants at high altitudes could paradoxically threaten many specialized alpine plants that are well adapted to harsh conditions but not very competitive. As conditions become favorable for growth, they are pushed out by more energetic, ordinary plants from lower altitudes.
“The unique biodiversity of the Alps is therefore under considerable pressure,” said Rumpf.
Unlike the vegetation, the snow cover above the tree line has changed more modestly, decreasing significantly in almost 10% of the area, which excludes glaciers and areas below 1700 meters. Researchers said this was still a worrying trend.
Professor Antoine Gizan of the University of Lausanne said: “Previous analyzes of satellite data have not identified such a trend. This may be due to the fact that the resolution of the satellite images was insufficient or because the periods considered were too short.
Although high-resolution data did not reveal changes in snow depth, ground-based measurements showed a reduction in depth at low altitudes for several years.
Scientists said that as larger areas of the Alps turn from white to green, feedback has been created, leading to increased rates of heating and melting snow.
“Greener mountains reflect less sunlight and therefore lead to additional warming – and in turn to further shrinkage of the reflective snow cover,” Rumpf said of the albedo effect.
Heating also causes further melting of glaciers and thawing of permafrost, which can lead to more landslides, rock falls and mudslides.
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