Jussi Paivinen and Marja Hokkanen

Around two thirds of Finland's land area is covered by forest. For hundreds of years, slash-and-burn agriculture and tar burning have influenced the structure of forests. Also, the intensive forestry practised after the Second World War has caused significant changes in forest habitats. Few natural forests remain, and they are fragmented and now found mainly in protected areas.

In natural boreal forests, decaying wood of varying size and in various stages of decay is formed all the time. The decaying wood originates from various tree species, and is far more abundant than in commercial forests. As trees fall, they create small openings where new saplings grow. Deciduous trees, which demand more light, grow in the slightly larger openings, whereas spruces grow in the more shaded ones. Due to the constant changes, a natural forest is like a mosaic. Trees of differing size and species grow in random order; occasional small openings are found, as well as thickets.

As a result of effective fire prevention, extensive forest fires hardly occur anymore in Finland. In the past, there were frequent forest fires that left behind dead or dying charred wood. If a forest fire is limited to ground level, the entire tree stand may survive. If the fire reaches the tree tops, at least some of the trees die, and sometimes all of them. Forest fires usually increase the mosaic nature of forests. After the fire, dead and decaying wood is found unevenly distributed in the forest. Saplings grow in the openings formed, and the variation in the age and species' distribution of the trees, as well as the spatial variation of the forest, is often increased.

Forests are the primary habitat for 564 (38 percent) of Finland's threatened species. Furthermore, some 60 (33 percent) forest-dwelling species have already gone extinct in Finland. Many more species have gone extinct from parts of the country, especially from the southern part, which has been most influenced, and for the longest period of time, by humans. Particularly invertebrates, especially beetles, as well as fungi have become extinct.

Only a small fraction of the forests in protected areas are being restored. It has been estimated that the forest area on mineral soil that needs to be restored is approximately 29,000 hectares in protected areas in Finland. In addition, many extensions that are to be joined to existing nature protected areas are in need of ecological restoration. During the years 2003 to 2012, 16,500 hectares of forest are to be restored in protected areas in southern and western Finland. The need for ecological restoration of forests will diminish in the future, because natural processes that create habitats for endangered species begin to take place.

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