Almost half of Swiss forests are unnatural

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Researchers from the Swiss Federal Forest, Snow and Landscape Research Institute (WSL) found the highest proportion of unnatural forests on the Swiss Plateau. “By its nature, deciduous forests will dominate the central plateau,” said Daniel Scherrer, the study’s first author, on Monday at the request of the Keystone-SDA news agency. However, since the 19th century, conifers, mainly spruce, have been planted during timber production.

The highest proportion of natural forests in Switzerland can be found at altitudes between 1400 and 1700 meters above sea level. There, the two most economically important conifers – spruce and silver fir – naturally dominate the stocks.

Forests classified as “natural” were significantly less susceptible to degradation than “non-native” forests. According to the information obtained, the spruce forests, especially in the Central Plateau, are susceptible to deterioration. Since spruce is not naturally found at low altitudes such as the Swiss Plateau, it is more affected by heat than other tree species.

“Bark beetles are very successfully infesting trees that are already stressed,” Scherrer explained. According to the study, the pests also benefit from warm lowland conditions that allow for several insect generations per year.

With global warming, this stress on spruces will increase,” he said. It is therefore important to make forests more natural again. “This change is already underway,” Scherrer said. Historic spruce forests are gradually being converted into deciduous forests.

However, this takes decades, if not centuries, due to the longevity of trees and the slow regeneration process. In addition, spruce is still used today. Spruce is still the most important tree species in Switzerland.

According to the study, the proportion of natural or semi-natural forests in Switzerland was 43 percent, slightly higher than in Germany (36 percent) or Austria (25 percent).

https://doi.org/10.1016/j.foreco.2023.120827

(SDA)

Source : Blick