Insects in the natural forest - a give and take
"The Sihlwald is home to many wood-loving insect species that depend on habitats that are as untouched as possible. Many of the most endangered beetles require thick deadwood and other typical natural forest elements," explains insect researcher Beat Wermelinger. Natural forests such as the Sihlwald thus enable a specialized 'species pool' to survive. They offer niches that managed forests do not have - but the reverse is also true: according to Wermelinger, for example, light-loving insect species are more common in forests where wood is regularly felled. In order to protect the many different insect species with very different requirements from extinction, both 'forest species' are needed. "As natural forests are scarce throughout Switzerland, reserves such as the Sihlwald are particularly important," says Beat Wermelinger.
Stepping stones to connect habitats
According to Wermelinger, individual isolated natural forests are not enough to ensure the survival of specialized insects in the long term. The insects must be able to exchange information, a large-scale connection is necessary. Suitable 'intermediate habitats' for the insects are essential for this: "An old tree or a large rootstock can be enough," explains the researcher. It is important that many such elements are within reach of the insects - for most species this is just a few kilometers. For Wermelinger it is clear: "The Sihlwald is a large and important piece of the mosaic in such a puzzle of habitats".
A natural forest needs insects
Insects perform various important functions in the natural cycle of the forest. They decompose dead trees and shrubs, releasing stored nutrients from the dead plants. They then make these available to the soil again. Other animal species such as birds feed on insects - sometimes exclusively. Not enough of a good thing: Insects skillfully and reliably regulate other species and thus keep them in check. For example, the bark beetle. Predatory mites suck out its eggs and various other predators love to eat its larvae. This leads to a natural regulation of the beetle. One thing is clear: no natural forest without insects, no insects without a natural forest.
