Mountain forests protect human beings efficiently and cost-effectively against avalanches and rockfalls. We are investigating which properties of a forest determine the level of protection it provides and how this could be altered by climate change.
Roughly half of Swiss forests protect lower-lying settlements, roads or railway lines against natural hazards like avalanches or rockfalls. Mountain forests provide key protection against avalanches. Snow cover in the forest is more stable than out in the open because: a) the treetops catch some of the snow; b) temperatures and wind conditions are better equalised in the forest interior; and c) tree stems support it. The more open a forest is, the worse the protection it provides against avalanches. The level of protection depends on the length and breadth of forest gaps and the forest's tree species composition.
After mountain forests' intensive use by our ancestors over centuries, over the last 150 years they have expanded, mostly becoming denser. In principle this enhanced the effectiveness of the protection they provide. However, natural disturbances such as storms or forest fires can change this protection in an instant. Climate change will also affect tree species composition and the structure of mountain forests. We are examining how disturbances and climate change will affect the protection provided by mountain forests. The results of our studies are fed, amongst other places, into RAMMS, a computer program used to simulate natural hazards, which can be used to calculate mass movements and gauge the impact of protective measures.
But mountain forests not only shelter us, they also provide wood, habitats for numerous animal and plant species, and recreational spaces for people. This makes their meaningful use no easy task, since all these interests need to be considered. Together with partner institutions, we are developing decision-making aids to optimise the protection provided by mountain forests, in harmony with other ecosystem functions.