More than 100 species
of animals, plants and fungi have already gone extinct from Finnish
forests. The current extinction debt of forest species in Finland
is around 1 000 species; this means that these 1 000 species will
disappear sooner or later unless the area of natural and semi-natural
forests increases significantly.
The
most important threats to forest species are the low amount of dead
wood in managed forests as well as the loss and degradation of the
forest types that are naturally most diverse, such as herb-rich
forests and old spruce forests. The amount of dead wood in managed
forests is so low, and the key biotopes that are currently preserved
in them are so isolated and small, that the threshold values for long-term
persistence of most threatened species are not met.
To remove
the extinction debt and avoid species going extinct requires that
the habitat quality of forests improve above the species’ threshold
values. In the case of species dependent on dead wood this implies
that the amount of dead wood at the forest stand level should be of
the order of 50 m3/ha (or somewhat less, 20–30 m3/ha, if this were
the average for larger areas). The current figure is around 3 m3/ha.
This target cannot be reached in all commercial forests, so it is
sensible to concentrate efforts at increasing amounts of dead wood
in smaller areas, including protected areas, where the threshold for
threatened species can be reached. However, the current network of
protected areas is not sufficient, as only around one per cent of
forests in South Finland are protected. Less than one per cent
of the forests in South Finland are currently in a natural or natural-like
state. More modest increases in the amount of dead wood in commercial
forests will facilitate the occurrence of many non-threatened species.
Estimates
by biologists suggest that increasing numbers of specialised forest
species become endangered when the area of natural and semi-natural
forests falls below 10–20 per cent of the forested land. Empirical
research results support these predictions. Applying the precautionary
principle, the target of forest protection should thus be set at
20 per cent, but a target of 10 per cent is acceptable if protected
forests and those to be restored are chosen carefully so that they
form a functional network of various forest types. Protection
of biodiversity in commercial forests in turn decreases the probability
of currently abundant species becoming threatened. Such softer methods
of forestry in commercial forests thereby help attain the overall
aims of species conservation.
[Excerpt
from an NGO-publication Palaako elävä metsä?]
