Climate risks: snow disappearing from the Alps

Snow is disappearing from the Alps and being replaced by increased vegetation due to climate change, scientists have warned.

Researchers from the universities of Basel and Lausanne, Switzerland, have published an article in the journal Science which has analysed almost 40 years of aerial images of the Alps, taken between 1984 and 2021 by four generations of satellite cameras, with the aim of quantifying how much vegetation has increased.

Professor Grégoire Mariéthoz, director of the Institute of Land Surface Dynamics at UNIL, and co-author of the study, said: “The ‘greening’ of the Alps was a known phenomenon, but it was not possible to measure the depth of this trend, which is now massive.”

“We were able to aggregate a lot of data and reach a level of detail never before achieved, showing, pixel by pixel, the temporal evolution of certain regions of the Alps. The fact that such a change is visible in less than forty years is an indication of the sensitivity of the Alps to global warming.”

The vegetation coverage of the Alps, at the tree line (about 1,700 metres altitude), has increased by 77%, the study showed. These new ‘fields’ now cover areas that were previously rock.

The findings confirm the effects of global warming in the area, as well as the retreat of major glaciers, said Professor Mariéthoz. Increased greenery sets off a cycle of increased warming, researchers said.

Professor Sabine Rumpf, the lead author of the study and head of the Ecology research group at the University of Basel, said: “Greener mountains mean less reflection of sunlight, which will further increase warming and in turn decrease the snow coverage and its reflectivity.”

Alpine biodiversity is already considered to be fragile, and is set to suffer even more as higher altitudes will be colonised by species that usually live at lower altitudes. Even though alpine species are generally very adaptive, they can lose their advantage if the environmental conditions change.

Professor Mariéthoz warned: “A flower such as the Edelweiss is especially threatened by this phenomenon.”

Professor Antoine Guisan, a professor at UNIL and co-author of the study, added: “Previous analyses of satellite data had not identified such a trend.”

While researchers had hoped that the increased vegetation could have a positive impact on CO2 absorption, they said that the biomass observed is rather small and its capture power is therefore very limited, so the effect should be negligible.

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