Forest fires ¶

Sustained periods of drought, which increase the risk of forest fire, have become increasingly common over the last thirty years. We systematically gather data of forest fires and develop methods and concepts to evaluate the risk and to learn about the fire ecology of tree species.

Around ninety percent of forest fires in Switzerland are caused by human activity: careless behaviour or arson. However, periods of low precipitation and extreme drought, which have been occurring more frequently for several decades, increase the risk of fires.

The accumulation of biomass in the forest also contributes to the forest fire risk: Combustible dead wood, fallen leaves or undergrowth are no longer collected, but accumulate on the forest floor. As a result, fire can spread very easily, especially during long periods of drought.

Forests in Switzerland burn most frequently on the southern side of the Alps, i.e. in Ticino and in the south-facing Grisons valleys - typically in spring. At this time, it is driest there, there is often a foehn and the deciduous trees do not yet have any leaves to protect the ground from the drying rays of the sun.

Forests in the central alpine valleys, especially in the Valais, burn somewhat less frequently - but on average 28 times a year since 2000. In recent years, there have also been more forest fires in the rest of northern Switzerland, but they remain small at present.