Targets for maintenance of dead wood for biodiversity conservation based on extinction thresholds

Forestry decreases the amount of dead wood, thereby threatening the persistence of many saproxylic (wood-living) organisms. In this article, we discuss how targets for efforts to maintain and restore dead wood in managed forest landscapes should be defined. We found several studies suggesting extinction thresholds for saproxylic organisms. However, because the thresholds differ among species, the relationship between species richness and habitat amount at the local scale is probably described by a smoothly increasing curve without any distinct threshold. The most demanding species require amounts of dead wood that are virtually impossible to reach in managed forests. This means that unmanaged protected forests are needed. In managed forests, conservation efforts should focus on the landscape scale and on certain types of dead wood, but it is impossible to come up with any particular amount of dead wood that is desirable at the forest stand level.