THE ALPS – CHANGING FAST
When Montagne Verte was created just two years ago, we alerted you to the fact that climate change in the Alps has led to an increase in temperature of almost twice the global average.
Steep cliffs, flowering alpine meadows, snowy coombes: the diverse and wild beauty of our mountains depends on all these microclimates and different ecosystems. In the Alps, the climate varies with altitude and along the slopes: we lose about 0.6° per 100m of altitude.
Change now becomes visible. Who hasn’t seen photos of our glaciers, true sentinels of global warming, which are retreating at a rapid pace?
Temperatures are rising, and in the Northern Alps, over the last 40 years, the duration of snow cover between 1100 m and 2500 m has been reduced by 5 weeks. The degradation of the permafrost, real cement of the mountains, is weakening mountain walls. More than 700 collapses were recorded in the Mont Blanc massif between 2007 and 2017.
The upheaval for flora and fauna is certainly less visible and less impressive than glacial retreat or rock falls but is just as durable and profound.
MILDER WINTER
We are all inevitably worried about warmer winters and lack of snow. What about wildlife of our mountain? A milder winter and a reduction in snow cover can be beneficial for some species.
But others are affected because they simply do not adapt. For plants, if the snow melts early in the spring, there is a significant risk of late frost.
The same applies to ptarmigan, mountain hare and stoats. They change clothing in winter to blend in with the white of winter; once the snow has melted, their camouflage is no longer effective against predators. The timing of the moult depends on the length of the day, not on the temperature or the snow.
A good snow cover also maintains a ground temperature of almost 0°. Snow is one of the best possible insulators for flora and for certain animals that take shelter in it. For marmots, the lack of snow no longer insulates their burrows. They consume more energy to warm up, which reduces their weight in spring. It has been found that the survival of young marmots decreases after a winter with less snow.
If the snow melts too early, some slopes are deprived of the gradual melting of snow that ensures water availability even in the height of summer.
Most of our mountain lakes are losing oxygen, due to higher temperatures in winter. As for Geneva Lake, the deepest waters of the lake have not been stirred for 9 consecutive years, which has consequences for aquatic biodiversity.
HIGHER THAN EVER
A major response to climate change is the general trend for species to move upwards to find their optimal habitat conditions. Plants and trees move upwards by an average of 30m per decade, insects by 45m and snails by 17m. When you know their top speed, you realise that this change can be considerable!
Because of the pyramid shape of the mountains, the space available is reduced at higher altitudes and offers less and less room for everyone in the future.
One of the best examples is the rock ptarmigan. A relic of the Ice Ages, with its feathered legs, which took its name Lagopus “hare’s feet”, it needs cold to reproduce and is too hot from 21°. In the eastern Swiss Alps, ptarmigan have been observed at increasingly higher altitudes, from 6 to 9 meters more per year. Its habitat is necessarily shrinking and is becoming a conservation concern.
The forest is also growing, the Alps are greening, which is also a double-edged sword. Abundance of trees is always welcomed, but the alpine grasslands and meadows are necessary for many species.
CHANGE OF CALENDAR
Another forced adaptation is the shifting of the dates of seasonal cycles.
Insects, reptiles and butterflies, which do not regulate their body temperature, are today advancing their seasonal cycle. This is not the case for birds and mammals, as their cycle is dictated by the length of the day rather than by temperature.
When we study mountain herbivores, we become aware of the perfect harmony of the animals with their environment. The calving date of chamois and ibex is in perfect symbiosis with the peak production of vegetation.
At high temperatures in spring, vegetation starts early but the plants lose nutrients quickly after flowering. The birth dates remain unchanged even though peak flowering and vegetation is increasingly advanced in the season. The perfect timing is then disrupted.
For chamois, spring is a crucial period because the females need to have plenty of food, but also quality to have optimal lactation and to start building up fat reserves. A female chamois weighs almost 25kg in spring and must gain almost 10kg during the summer.
Male ibexes born in a warm spring will have smaller horns throughout their lives than their counterparts born in a cooler spring. Cooler springs provide good quality, highly nutritious food and favourable body condition for the mother at the end of gestation, so good quality milk and plant for the young ibex to ingest during its first summer.
Summer temperatures that are too hot will also stop the growth of plants and therefore limit the possible resources for wildlife before winter. Studies have shown that fewer ibexes were born in years following hot summers. This shows that female ibexes do not build up sufficient reserves during hot summers to ensure a successful pregnancy the following year.
WHAT DO WE DO NEXT?
As we wonder about the adaptation of these species, familiar inhabitants of our mountains, and sadly observe that this well-tuned score is being disrupted, how can we not ask ourselves how we too should adapt to the future of our singular environment?
Be discreet inhabitants, preserve our cultural, economic, and emotional habitats and make room for the extraordinary biodiversity of our landscapes.
Take care of our valleys and summits, so that our visitors will still have wild spaces to dream and escape.
Slow down, anchor nature in our thoughts and in our future decisions.
Sources: Atlas du Mont-Blanc par le CREA, OFB, CNRS, Magazine Salamandre, CIPEL, Nature losing its bearings by Crea, Vogelwarte, Wsl.ch
Words: Alice de Chilly
