Deadwood in the Sihlwald
Over 6,000 species depend on it
The name «deadwood» can be misleading, as broken branches and dead trees ensure the survival of many species. One of these is the abraeus parvulus beetle, a primeval forest relict species that depends on natural forest structures.
Old and dead trees are important for biodiversity. In Swiss forests, around a quarter of all species depend on old and dead wood. According to the Federal Office for the Environment, there are around 6,000 species in total. These include around 2,500 fungi, 1,300 beetles, 670 lichens and 130 snails – but also numerous other insects as well as birds, small mammals, amphibians and reptiles, for which old and dead trunks provide breeding cavities, food, cover, or a moist environment.
The old-growth and deadwood fauna is one of the most endangered communities in Central Europe. This makes natural forest reserves such as the Sihlwald all the more important. They are an important building block for the preservation of biodiversity.
Much more deadwood than 25 years ago
Commercial use of the Sihlwald forest was discontinued 25 years ago. Since then, the volume of deadwood in the Sihlwald has almost doubled and has grown to over 50 m³ per hectare. This is twice the Swiss average and even three times the average for the Swiss Central Plateau (Source: Swiss National Forest Inventory, p. 218).
Extreme events such as storms, heat and drought have also greatly accelerated the natural forest cycle in the Sihlwald since 2018. The return to a natural forest structure and areas with late forest phases is progressing faster than originally expected.
As a result, the Sihlwald is developing into an essential habitat for a whole range of fungi, lichens, mosses, beetles and vertebrates. This also includes primeval forest relict species such as the abraeus parvulus beetle, which are dependent on natural forest structures. The Sihlwald forest is one of the few locations in Switzerland where this species has been recorded.
