A statement that sends shivers down your spine.
The current snow cover in the Alps has decreased by 36 days compared to "
the long-term average
", according to a study by the scientific journal
Nature Climate Change
, published on January 12.
An unprecedented drop in the last six centuries.
For scientists, global warming is the main culprit.
"
The snow arrives later and later and melts faster and faster
," laments Marco Carrer, co-author of the report and teacher-researcher in forest ecology at the University of Padua, Italy.
The study shows that over the last fifty years, the duration of snow cover in the Alps has decreased by 5.6% per decade.
“
Duration during which the snow persists on the ground
”, he specifies.
Added to this is a decrease of 8.4% per decade, between 1971 and 2019, in the thickness of this snowpack.
Tree ring study
If this alarming situation was “
relatively known
”, the
Nature Climate Change
report allows us to “
go back in time
”, welcomes Louis Ravanel, CNRS research director, at the Mountain Environments, Dynamics and Territories Laboratory.
Thanks to the study of tree
rings (Editor's note: circle located in the trunk of a tree, corresponding to its annual growth)
, the four Italian scientists were able to determine the duration of the snowpack over several past decades.
“
We lacked this historical depth
,” explains Louis Ravanel.
Read alsoGlobal warming: concern in the high mountains before the end of summer
For this, the experts focused on "
dwarf
" trees, more precisely on 572 juniper shrubs.
These trees, some
of which are “nearly 600 years old, counting the dead branches collected
” specifies Marco Carrer, were chosen for their small size because they are covered with snow for most of the year.
Thus, the more or less long duration of the snowpack on these trees modifies the width of the tree rings.
This study made it possible to determine the snowpack for the first time more than a century ago, thus compensating for the lack of meteorological data on the question.
Multiple impacts
Global warming is clearly named culprit by scientists.
Louis Ravanel even speaks of a “
vicious circle
”.
“
Snow has an essential function: its white surface reflects solar radiation, which reduces global warming
”.
The absence of snow at altitude therefore gives the opportunity for the heat to set in and cause damage.
The repercussions of this reduction in snow cover are multiple, in particular on plant and animal species at altitude “
accustomed to living in the presence of snow
”, reports the Italian researcher.
"
Some of them live protected under the snow during the winter
", develops Louis Ravanel.
Read alsoGlobal warming: artificial snow, a fragile second best
The mountain economy, focused on tourism and skiing, also suffers the consequences.
“
The shorter the snow cover period, the shorter the ski season
,” continues the CNRS research director.
The water cycle is also disrupted.
The snow present on the glaciers is a "
reservoir of fresh water
", "
billions of humans depend on it
".
Coping Strategies
"
There is no short-term solution
," says Marco Carrer.
“
Creating new ski areas using artificial snow will not solve the problem
”.
Saving water is becoming a priority because "
it could be greatly reduced in the years to come
", warns the researcher.
Read alsoDo mid-altitude ski resorts still have a future?
For its part, the
Nature Climate Change
study recommends developing adaptation strategies for the most vulnerable sectors.
Louis Ravanel particularly considers it necessary to diversify the mountain economy, “
so that it is no longer dependent on skiing
”.