Global heating is turning white Alps green, study finds

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The impact of global warming on the Alps is obvious from space, with the snow-white mountains being increasingly inhabited by green flora, a study of high-resolution satellite data revealed.

According to the study, vegetation above the treeline in the Alps has increased by 77% since 1984. While receding glaciers have represented the rate of global warming in the Alpine region, experts have termed increases in plant biomass as an "extremely tremendous" change.

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Rising temperatures and greater precipitation are extending the growing season, causing plants to colonize new areas and grow denser and taller. Snow cover is thinning, and scientists say that losses of less than 10% of snow cover above the treeline are nevertheless substantial.

“The scale of the change has turned out to be absolutely massive in the Alps,” said Prof Sabine Rumpf, of the University of Basel, and lead author of the paper which was published in Science.

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Mountain regions are warming roughly twice as quickly as the worldwide average. While the greening of the Alps may improve carbon sequestration, it is anticipated that this will be balanced by negative consequences such as thawing permafrost, which is a reduced albedo effect (less snow reflecting away sunlight), and habitat loss.

Rumpf explained that more plants at high altitudes could paradoxically threaten many specialist Alpine plants, which are well adapted to harsh conditions but not very competitive. As conditions improve for growth, these are pushed out by more vigorous, common species from lower elevations.

“The unique biodiversity of the Alps is therefore under considerable pressure,” said Rumpf.

Snow cover above the treeline has altered less dramatically than vegetation, falling significantly in nearly 10% of the region (excluding glaciers and places below 1,700 meters). According to the researchers, this is still a concerning trend.

Prof Antoine Guisan, of the University of Lausanne, said, “Previous analyses of satellite data hadn’t identified any such trend. This may be because the resolution of the satellite images was insufficient or because the periods considered were too short.”

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Although high-resolution data cannot identify changes in snow depth, ground-based observations have shown depth decreases at low elevations for several years.

The scientists revealed that when bigger portions of the Alps went from white to green, a feedback loop was generated, resulting in a faster rate of heating and snow melt.

“Greener mountains reflect less sunlight and therefore lead to further warming – and, in turn, to further shrinkage of reflective snow cover,” Rumpf said of the albedo effect.

Heating also causes glaciers to melt and permafrost to thaw, potentially leading to greater landslides, rockfalls, and mudflows.