Forest damage caused by beetle infestation
Various insects can colonise weakened trees and cause them to die. Trees that are weakened through age, disease or stress are eradicated through this process, which promotes the health of the forest and its resilience. However, when these insects proliferate during extended periods of heat or drought or in the aftermath of storms, healthy trees may also be adversely affected; in the worst-case scenario, entire forests die.
Insect infestation increased considerably in the aftermath of cyclone Lothar in the winter of 1999/2000, but fell sharply after 2003, before increasing again starting in 2013.
In 2017, spruce stands were infected, especially in the lower altitudes of the Central Plateau, in parts of Grisons and the Southern Alps.
After the increase in 2013, European spruce bark beetle (Ips typographus) infestation has remained consistently high since 2014. While the situation in northern Switzerland was quiet, the infestation increased significantly in individual mountain regions, such as in Grisons and Valais. In many cases, this increase is explained by the regional storm and snow pressure damage in the last two years.
While it is inappropriate to classify the situation as a new instance of mass bark beetle proliferation, the problem can be expected to worsen in the medium to long term due to more extreme weather events such as drought and storms that come with climate change. Bark beetle activity will likely be benefitted by higher temperatures and the consequences of storms.
The indicator can be compared internationally only to a limited extent as different tree and beetle species are recorded (only European spruce bark beetles and spruces are recorded in Switzerland; other/additional tree species and bark beetle species are recorded abroad. Note: The damage caused by insect infestation is recorded internationally in hectares of forest area).
The data are collected through a survey of all forest districts in Switzerland. Only European spruce bark beetles and spruces are recorded for this indicator, which covers 80% to 85% of the damage caused by bark beetles. Infestations of other insect species are also surveyed by Swiss Forest Protection through a survey of forest wardens.