Background: Conservation of biological diversity and economical utilization of natural resources form an almost inevitable confrontation between the two. In practice, however, a balance between the two ought to be found, and in managed boreal forests, preservation of woodland key habitats is increasingly used strategy to safeguard biological diversity. According to the Finnish Forests Act, certain Forest Act habitat (FAH) types must be safeguarded, provided they are clearly distinguishable from their surroundings. Furthermore, once the habitat has been identified as a FAH, its special characteristics must not be altered. Both of these aspects contain ambiguities that potentially undermine the practical application of the Act. We designed a replicated sampling study to address these ambiguities at the most common FAH type, riparian habitat of small boreal streams. As response variables we used vascular plants and mosses. We asked i) how wide is the FAH around small streams that is distinguishable from its surrounding and ii) how wide buffer strip around the FAH is sufficient for long term to preserve the natural species community composition of the FAH.
Results: We found that an average three meters wide strip around the stream constitutes the distinguishable FAH and that a minimum of 45 meters wide buffers on both sides of the stream are needed for the species community composition to remain unaltered.
Conclusions: We conclude that 45 meters wide buffers appear sufficient to safeguard vascular plant and moss species communities within the FAH, prevent local populations from extinctions and thus pre-empt extinction debt that would be realised with more narrow buffers. While 45 meters may seem intolerable from the commercial forestry point of view, anything less than that may be intolerable from the point of view of conservation, and thus against the idea of sustainable use of natural resources.