Authors: Elisabeth Pötzelsberger (EFI), Andreas Schuck (EFI), Michael den Herder (EFI)
Most forests in Europe have a long history of human use and have been altered in one way or another. Still, forests are one of the ecosystems with the highest biodiversity. Old-growth and natural forests are particularly valuable for biodiversity and carbon storage. Some intensively managed forests (e.g. coppice forests) can also have high conservation value.
Today 94% of Europe’s forests are classified as ‘semi-natural’ (with regards to tree species composition, regeneration, age and stand structure), 2% are undisturbed by man (mainly found in North, South-East and Central Europe) and 3% are plantations. Since the majority of forests is managed (including forests with a less strict protection status, e.g. Natura 2000 sites), forest biodiversity conservation heavily depends on best-practices of forest management. However, in nearly 24% of European forests, management must take special care to conserve biodiversity as stipulated by the EU Birds and Habitats Directives.
Very often the impact on biodiversity depends on the intensity of forest management. High intensity measures like clear-cutting result in the temporary removal of all trees. Reduced impact logging, like single tree selection, is an example of a low intensity timber harvesting technique. All types of management change some properties of the forest and hence may favour some species - e.g. light loving species in a clear-cut system - while disadvantaging others.
Forests managed primarily for timber production often lack the late development phases found in natural forest ecosystems. Many species live or are dependent on habitat trees, typically large and old trees that bear microhabitat structures such as cavities, cracks, breakages, deadwood, epiphytes or provide possibilities for nest building. Lying and standing deadwood is home to many specialized organisms, in particular saproxylic invertebrates (e.g. insects) and wood decomposing fungi, and in addition contributes to improving the nutrient balance in soils and to preserving water. It is therefore of high importance for biodiversity to integrate these elements of old-growth stages into forests managed for wood supply, i.e. considerable amounts of deadwood, old trees with microhabitats, diverse stand structures or forest gaps.
Forest management may also aim to increase biodiversity through mimicking natural disturbances, e.g. by prescribed burning, creating gaps of different sizes, and increasing the amount of coarse woody debris.
In addition, the choice of site-adapted tree species is a fundamental forest management decision that influences biodiversity. This not only directly influences tree species diversity, but indirectly affects forest biodiversity, as numerous species have co-evolved and thus depend on specific tree species or species groups. A prominent example is the spotted nutcracker that in its European range depends heavily on the nuts of Swiss pine. The lack of co-evolution is often the reason why, overall, fewer native animal species profit from introduced tree species.
Forest management practices influence forest structure and biodiversity in many different ways, but there is no one-sizefits- all-solution for optimizing biodiversity in forests because of the different demands of forest dwelling species. While forests managed for a range of different ecosystem services will always differ from natural forest ecosystems, silviculture has many options to better integrate biodiversity conservation by imitating natural processes and integrating old-growth forest elements.