Researchers in Italy have traced 600 years of snow cover in Val Ventina, a region of the Italian Alps, thanks to the study of shrubs. The results show a steady decline in the annual amount of snow.
The duration of snow cover at 2,000 meters has been shortened by 36 days compared to the long-term average over the past century, with an acceleration in the past 50 years.
This evolution, unprecedented in six centuries, can be linked to climate change, according to the report published in the scientific journal Nature on 12 January 2023.
"Over the past 50 years, the Alps have experienced a 5.6 percent reduction in the duration of its snow cover per decade, which is already affecting a region where the economy and culture are largely centered on winter activities," the report said.
Researchers also found that the average depth of the snow cover between November and May had decreased by 8.4 percent per decade, between 1971 and 2019.
Previous research has already shown that the snow cover over the whole of the Alpine mountain range in Europe has been declining by about 5 days every 10 years since the 1970s.
This latest study examines snow cover since the end of the Middle Ages.
Consequences
The oldest snow reports date from the 18th century, so to find out what winters looked like centuries ago, the researchers turned to studying the rings of a particular type of shrub from the Val Ventina region of the Italian Alps (an area around 400 kms east of the French Alps).
For the report, the researchers studied more than 572 samples of juniper trunks (Juniperus communis), high-altitude trees (between 2,100 and 2,400 m above sea level) that have the particularity of living for a long time and which grow lying close to the ground.
Their growth stops as soon as there is snow on the ground, and these periods of growth stoppage can be read in the width of their tree rings. Each of these rings corresponds to the layers of cells that develop each year when the sap circulates and the trunk grows.
This is why these junipers indirectly archive the snow levels of the past.
The researchers warned that the consequences of reduced snow cover are wide reaching. One the one hand, many species dependent on snow or adapted to cold are now facing a decline in their numbers and their reproductive capacity.
On the other hand, tourism and recreational activities are likely to suffer from the reduction of snow cover.
Already low mountain ski resorts and towns that depend on snowfall for their economies have begun looking for solutions in this new climatic context.
Key water supplies
"It is a very robust study, and this methodology deserves to be repeated in other regions of the Alps," Samuel Morin, researcher at CNRS and the French Meterological Bureau (Météo France), told Radio France website on Tuesday.
Experts agree that this decline in the snowpack, linked to global warming, not only damages the economy of ski resorts, but also limits key water supplies in numerous countries.
The snow of the Alps is a reservoir of water which supplies large rivers across central and southern Europe. A decrease in this water reserve could have repercussions on the local environment and the demand for agricultural, industrial and domestic purposes.
"The Alps are the most important water-supplying mountain range in Europe, with the Danube, Rhine, Rhône and Po being the main drainage basins and the Po river basin, on the southern side of the Alps, deemed the second most sensitive area, after the Rhône basin," the authors wrote.
The researchers underlined "the urgent need to develop adaptation strategies" to help this region cope with the effects of global warming caused by human activities.
