The impact of global warming in the Alps is visible from space, with snow-white mountains increasingly colonized by green plants, according to a study of high-resolution satellite data.
Vegetated areas above the tree line in the Alps have increased by 77% since 1984, the study says. While retreating glaciers have symbolized the rate of global warming in the Alpine region, researchers described the increase in plant biomass as an “absolutely massive” change.
Rising temperatures and rising rainfall are lengthening the growing season, with plants colonizing new areas and becoming denser and taller. Snow cover is declining and scientists said losses of less than 10% of snow cover above the tree line were still significant.
“The scale of change has turned out to be absolutely massive in the Alps,” said Sabine Rumpf, a professor at the University of Basel and lead author of the paper, which was published in Science.
Mountain areas are warming about twice as fast as the world average. And while greening in the Alps could increase carbon sequestration, this is likely to be offset by negative implications, including permafrost thawing, a reduced albedo effect (less snow reflecting sunlight), and loss of carbon dioxide. habitat.
According to Rumpf, more high-altitude plants could paradoxically threaten many specialized alpine plants, which adapt well to harsh conditions but are not very competitive. As conditions become favorable for growth, these are overwhelmed by more vigorous and common plants of lower altitudes.
“Therefore, the unique biodiversity of the Alps is under considerable pressure,” Rumpf said.
In contrast to the vegetation, the snow cover above the tree line has changed more modestly, decreasing significantly by almost 10% of the area, which excludes glaciers and areas below 1,700 meters. Researchers said this was still a worrying trend.
Professor Antoine Guisan of the University of Lausanne said: “Preliminary analyzes of satellite data have not identified any such trends. This may be because the resolution of the satellite images was insufficient or because the periods considered were too short “.
Although high-resolution data do not detect changes in snow depth, ground measurements have shown decreases in depth at low elevations for some years.
Scientists said that as the larger areas of the Alps went from white to green, a feedback loop was created that caused an increase in the rate of warming and melting snow.
“Greener mountains reflect less sunlight and therefore lead to additional warming and, in turn, greater shrinkage of the reflective snow cover,” Rumpf said of the albedo effect.
Warming also causes more glacier thawing and permafrost thawing, which can cause more landslides, rock falls and mudslides.