Unmanaged forests are needed to ensure biodiversity conservation in European forest landscapes

Uniform and intensive forest management approaches threaten European forest biodiversity. There are many different ways to manage forests, but the effects of different combinations of approaches are not well understood. An international research team led by the University of Göttingen (Germany) and University of Jyväskylä (Finland) investigated how the Triad forest management framework can support biodiversity conservation in European beech forests. In Triad forest management, forest areas are classified following forest management categories: intensively managed forests (with clearcutting – meaning harvesting all or nearly all the trees from an area), unmanaged areas (no harvesting in recent years) and extensively managed forest (partial harvests without clearcutting and dominated by native tree species). 

- Triad forest management means dividing a landscape into three zones, which are managed differently. The Triad framework seeks to balance the economic and ecological functions in forested landscapes by combining intensively, extensively, and unmanaged areas. It assumes that extensively managed forests support more biodiversity than intensively managed ones, and unmanaged forests support more than managed forests, specifies Senior Researcher Rémi Duflot from University of Jyväskylä.  

Virtual landscapes were used to study forest biodiversity 

The research group quantified the effects of using different proportions of the three management zones in a landscape on the diversity of a wide range of species groups including birds, beetles, plants, lichens and fungi. The original data were collected from nine sites in France, Germany, Italy and Czechia. 

- The originality of our method was to develop ‘‘virtual” landscapes using computer analysis, in which data could be resampled. It enabled us to create landscapes that vary in proportion of extensively, intensively, and unmanaged forests, and explore the whole range of possibilities, says researcher Dr. Peter Schall, University of Göttingen. 

Unmanaged forests and forest heterogeneity promotes biodiversity 

The researchers found that species diversity was highest in landscapes composed of 60 percent unmanaged and 40 percent intensively managed forests. Diversity was lowest in purely intensively managed landscapes, but extensively managed forests contributed little to support species richness. However, it would be unrealistic to have 60 percent unmanaged forests in Europe due to the rising demand for wood, which is why the authors suggest focusing on improving the ecological performance of extensive management.  

- To preserve forest biodiversity in Europe, we recommend increasing the proportion of unmanaged forests and promoting forest heterogeneity in extensive management – for instance by providing a mosaic of open and closed canopy forest patches and keeping large old trees and deadwood in the forests, explains Duflot. 

The results were published in the journal PNAS. The study was supported by the EU Framework Programme Horizon 2020 via COST, the German Research Foundation (DFG), and the Kone Foundation. 

Article information:  

• Duflot et al “Sustainable forest planning: assessing biodiversity effects of Triad zoning based on empirical data and virtual landscapes,” Proceedings of the National Academy of Sciences (PNAS) (2025). 
• DoI numer: https://doi.org/10.1073/pnas.2512683122 
• Link to article: https://www.pnas.org/doi/10.1073/pnas.2512683122  

Further information:  

• Dr. Peter Schall, University of Göttingen, +49 (0)551 3928994, peter.schall@forst.uni-goettingen.de  
  www.uni-goettingen.de/en/77271.html  
• Dr. Rémi Duflot, University of Jyväskylä, remi.r.duflot@jyu.fi   
  www.remiduflot.com/