Threatened species are a clear indicator

The most significant impact of forestry on forest environments are caused by final felling and thinning, as well as by timber harvesting, forest drainage, soil cultivation, prescribed burning and fertilisation.

The clearest measurement of the impact of forestry on forest biodiversity is the number of threatened species. The Finnish Ministry for the Environment first surveyed the number of threatened species in 1985. The following survey was completed in 1990 and the most recent in 2000. The latest survey is partly based on principles different from the previous ones, so that it does not provide a completely reliable assessment of the development of the number of threatened species. However, when the 2000 survey was re-done on the principles used earlier, it was noted that the number of threatened species had increased by a scant third. Nevertheless the rate of increase in the number of threatened forest species has slowed down during the 1990s.

In the 2000 survey about 19,000 of the total of 43,000 species in Finland were assessed, but the data was considered sufficient for only about 15,000 species. Among them about one tenth, or 1,505 species, were assessed to be threatened. About 560 of them, or 37.5 percent, live in forests. Not all of them are threatened expressly by forestry, for they can also be threatened by small predators or hunting, for example. Use of forest in itself is primary threat for 8.8 percent of all threatened species in Finland. Changes in the proportion of tree species threaten 6.7 percent, changes in the age structure of forests threaten 8.8 percent, and decrease of decayed wood in forests threatens 10.6 percent of the threatened species.

Overall it may therefore be said that forestry is primary threat for 34.7 percent of the threatened species. Drainage and peat harvesting form the primary threat for 3.2 percent of all threatened species in Finland.

Researchers also speak about factors threatening the species in the future. Forestry and forest management are responsible for these factors for 30.2 percent of threatened species. So, the rate of increase in the number of threatened species is not the worst in forest, but mostly among species associated with human culture which live in agricultural environments.

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