Snow of Tomorrow | The mountain forest: a changing foundation

The mountain forest is more than just a random collection of trees in the mountains, but a finely balanced system that stretches from the valley areas with less snow to the tree line. Beyond this line, in the so-called Krummholz zone, mountain pines and dwarf shrubs take over before the alpine barrenness begins. Changing slope gradients, short vegetation periods, snow and avalanche paths characterize this habitat, in which every metre of altitude balances between stability and destruction.

Depending on the exposure and altitude, spruce, fir, larch, beech, sycamore or Swiss stone pine dominate here - a diversity that has adapted to wind, cold and steepness over thousands of years. Rupert Seidl, one of the most renowned forestry scientists from the Technical University of Munich, describes the mountain forest as a dynamic system that has always been in a state of flux. However, he emphasizes that change is happening more rapidly today than ever before. This is important to emphasize because the significance of this goes far beyond what our naked eye can see today.

Heat stress and sweat

However, a look at the temperature curves and climate diagrams shows that all these functions are becoming more fragile. As the climate warms, the Alps are warming at around twice the global average. In the specialist literature, this effect is described as "alpine amplification" - an altitude-dependent warming that increases with rising sea level. According to research by the Oxford Research Encyclopedia of Climate Science, the zero degree line in the Alps and therefore also the snow line has been rising significantly for decades. In turn, the duration of closed snow cover is decreasing and the energy flows on the surface are changing. A central mechanism here is the so-called albedo feedback, because if the light snow cover disappears, darker soils and rocks absorb more solar radiation, the environment warms up even faster and the snow melts earlier.

Studies by the European Environment Agency show that the number of snow days in the central Alpine regions has decreased by up to a third since 1971. This has particularly affected the altitudes through which our access routes pass and where the protective forests are located. At the same time, the mountain is literally losing its grip. When the permafrost thaws, the "cement" that holds the rock faces together disappears. The Swiss Federal Office for the Environment has been documenting rockfalls, mudslides and landslides due to thawing soils for years. In practice, this is reflected in closed paths, demolished moraines, costly safety work and in extreme cases, such as in Blatten in the Swiss canton of Valais in May of this year, when an entire village was buried by falling masses. For forestry, this means, among other things, that slopes are endangered by material at higher altitudes, vegetation zones are shifting and tree species boundaries are changing.

The atmosphere also plays a role in the effects of climate change on the Alps, as the Alpine arc is located in Central Europe and is therefore surrounded by Atlantic low pressure systems, Mediterranean cyclones and foehn influences. Warmer air masses from the Mediterranean region contain more water vapor, which rains down on the southern slopes of the Alps. This increases the potential for heavy precipitation there. These peak loads hit protective forests harder than any average values. At these times, every tree and every cubic meter of forest soil counts, because the forest then has to perform in seconds what it has taken decades to grow. Unfortunately, the pressure is not only growing due to the changing climate: tourism and winter sports also have a direct impact on the forest. Artificial snowmaking, slope grooming, the construction of forest roads and other tourist uses are also changing the microclimate of the forest, its soil and the water balance. Studies by the Alpine Convention indicate that these influences fragment habitats and further increase the pressure to adapt. A more sustainable infrastructure is therefore no longer an option, but a prerequisite for the survival of many Alpine ecosystems.

What do the changes listed above actually mean for the mountain forest and what consequences do they have?

As mentioned, the vegetation zones are migrating. Deciduous trees such as beech and maple are migrating up the slopes, while spruce trees are coming under pressure as they are weakened by drought and heat. The years 2018 to 2020 are considered a warning signal in forestry research: prolonged drought and high temperatures led to large-scale bark beetle infestations. Even locations that were previously considered too cool are now affected.

According to data from APA Science, entire slopes were destroyed, and the mountain forest was not spared either. Today, damage occurs in cascades: After extreme weather events such as storms or snowfall, broken wood remains, providing ideal conditions for beetles and primary pests. If fungi and secondary pests follow, entire forest stands collapse. This process can happen faster than previously assumed. The Bavarian State Office for Forests and Forestry describes these chains of disturbance as one of the greatest threats to protective forests. At the same time, the aforementioned loss of permafrost and heavy rainfall are causing the loss of old protective structures and driving erosion. Young forests then need decades to develop the same protective effect - decades that we hardly have in an accelerating climate.

Tracks in the snow, tracks in our consciousness

As emphasized, climate change is not the only stress factor for the mountain forest. In addition to man-made climate change, we are also increasing the direct pressure on the forest, often without meaning to. Careless winter sports such as freeriding in the forest can compact soils, injure young trees and destroy protective layers of snow. Young forests are particularly at risk, as their seedlings are barely visible under the snow cover. Where steel edges of skis and snowboards cut off terminal shoots, the young growth is stunted and natural regeneration comes to a standstill. In the long term, this also damages the protective function of the forest, which is so crucial in times of climatic instability.

The consequences for wildlife are even more serious. In winter, many alpine species live at the energy minimum. Chamois, ibex and red deer lower their metabolism, reduce their heart rate and body temperature in order to save calories. Studies by the Hohe Tauern National Park show that disturbances during this time can be life-threatening. A startled animal consumes as much energy in a few minutes as it would otherwise save in a whole day. The same applies to grouse - snow grouse, black grouse and capercaillie - which spend the winter in snow caves they have dug themselves. If their rest is disturbed, they lose energy that they cannot replace during the harsh winter. This is why initiatives such as "Respect Wildlife" or "Bergwelt Tirol - Miteinander erleben" appeal to us all to be considerate when out and about. Those who respect wildlife quiet zones, avoid twilight hours, keep dogs on a lead and choose familiar routes not only protect animals, but also the stability of the entire system.

After all, a disturbed, weakened forest loses its protective effect, both for mountain villages and for the infrastructure that we use as a matter of course. Roads, parking lots, ski lift routes and slopes are all beneficiaries of the mountain forest, without the declared protective function of the forest, soil erosion would literally pull the ground from under the feet of many structures. It is therefore important to understand that the mountain forest is far more than just a backdrop for our enjoyment. It absorbs wind, holds snow, filters water, stabilizes slopes and cools the microclimate. It ensures that our tours are safe and, last but not least, that snow stays a little longer in the shade near the forest in winters with little snow. In times of rising zero-degree temperatures, this is a value that we cannot do without. Without healthy forests, there are no stable snow fields, no safe access routes, no reliable powder luck.

Unfortunately, fewer snow days, more unstable slopes and more frequent extreme events are already a reality. For regions dependent on winter tourism, adaptation is therefore becoming a question of survival. Artificial snowmaking may help in the short term, but it shifts water and energy balances. In the long term, only forests that are strong and diverse will contribute to functional protection and water management. And so an unpleasant lesson remains to be learned: Climate change is threatening the mountain forest - and therefore also winter sports. We can only enjoy the snow as freely as we manage to treat the forest fairly. Responsibility for the forest is not a contradiction to the passion of skiing and touring, but a prerequisite. It manifests itself in small decisions - in respect for wildlife rest areas, in conscious travel and movement, in avoiding unnecessary tracks. Researchers such as Julia Pongratz or Rupert Seidl show that adaptation is possible if we take it seriously and projects such as the "Klimafitte Bergwald Osttirol" prove that commitment works at a local level. The snow of tomorrow depends on the forest of today. And it will only remain strong if we see it for what it is: our silent, irreplaceable partner.