28 November 2025 | Article

Dead Wood Boosts Biodiversity 

Dead wood is not waste but vital habitat. A new Swedish study shows that older, protected forests with much dead wood host far more beetle species than production forests, underlining how important it is to keep dead trees in the forest. 

Forests are important for both nature and people. They provide timber, food, clean water, carbon storage and places for recreation. About 31% of the world’s land area is covered by forest. In Europe, around 75% of forest land is used for wood production, and in Sweden the figure is about 87%. This strong focus on timber affects forest structure and which species can live there. 

In Fennoscandia (Sweden, Norway, Finland and parts of north-west Russia), around 7,500 forest species are saproxylic – meaning they depend on dead or dying trees for some part of their life cycle. In a recent study from Linköping University, researchers compared the number and composition of dead-wood-dependent beetle species in Swedish forests. The aim was to quantify differences in both the volume of dead wood and the diversity of saproxylic beetles. 

The comparison included production forests of different ages as well as nature reserves. The results showed that 35–45-year-old stands were as species-poor as 15–25-year-old stands. Nature reserves contained roughly 5–10 times more dead wood per hectare than areas that had been clear-cut 65–85 years ago. Across all investigated species groups, the highest number of species was found in both new and old nature reserves and in 65–85-year-old stands. The lowest numbers of species were recorded in 15–25- and 35–45-year-old production forests.

Old nature reserves stood out with unique species, more red-listed species and a higher frequency of indicator species associated with high conservation value. Production forests aged 65–85 years were partly similar to new nature reserves in terms of total species and obligate saproxylic species, but they hosted fewer red-listed and otherwise conservation-important species.

Overall, the study shows that forest age and protection status strongly influence which species are present, and that older, protected forests – together with the long-term management history of a stand – are crucial for maintaining the diversity of saproxylic beetles. Dead wood is not waste material, but a cornerstone of forest biodiversity.

Photo: fightCOtwo