The number of species in Finland totals around 50,000, including all animal, plant and fungal species. Of these, some 20,000 live in forests. Of forest species, around 2,250 are threatened to various degrees. The number of threatened forest species is highest among fungi and invertebrates.
The structure and age of a forest stand is a key factor influencing species richness and species composition. The number of species is highest immediately after strong disturbance, such as a forest fire or clear-cutting. On the other hand, an old natural forest is significantly richer in species than an old commercial forest. The difference is largely due to the higher quantity of coarse woody debris at different stages of decay in an old growth forest.
Forestry, climate change and changes in agricultural environments affect biodiversity
More than one third of threatened species in Finland are forest species. Forestry is the key factor affecting forest biodiversity, because it has significantly reduced the occurrence of natural disturbances such as forest fires and the quantity of old trees and decaying and dead wood.
Climate change poses another major threat to diversity. It is altering the distribution ranges of species and may result in extinctions. The Intergovernmental Panel on Climate Change, the IPCC, estimates that a 2–3 degree rise in the global average temperature by 2100 will increase the risk of extinction for 20 to 30 percent of the world’s species.
As semi-agricultural wooded environments, such as meadows, dry meadows and wooded pastures become overgrown and afforested, biodiversity is undermined. This is due to the decrease in the number of grazing animals. Almost one fourth of endangered species require meadow, a dry meadow, a wooded pasture or another type of woody agricultural heritage habitat.
Diversity can be maintained even in commercial forests
Research findings suggest that silvicultural methods which emulate natural disturbances and natural development of forests provide more habitats for species in commercial forests. Management of uneven-aged forest stands is one of the possible solutions. Not only is this type of silviculture beneficial in terms of species and recreation, on suitable sites it can also provide revenue on a par with that of even-aged forest management. Factors driving natural disturbances in forests include forest fires, windthrows, and small-scale mortality due to insects and fungi.
Forest biodiversity can be actively promoted in commercial forests by a range of methods, including the removal of spruce from herb-rich forests, the retention of dead and decaying trees during felling, increased green-tree retention on regeneration areas, or controlled burning. Further management methods include the restoration of drained mires to their natural state by blocking the ditches and harvesting the trees on them.
Luke pursues research on the restoration of nature and monitors the METSO programme
The aim of the Forest Biodiversity Programme for Southern Finland METSO is to halt the decline of forest habitats and forest species, creating a favourable trend in forest biodiversity by 2025. Natural Resources Institute Finland (Luke) collects and reports monitoring information on the implementation of the METSO programme and produces research-based information on the implementation of the programme objectives and development needs, both from a socio-economic and ecological perspective.
Photo on top of the page: Reijo Penttilä