Impacts of clearcut accumulation on boreal forest bird communities: Defining a safe operating space at the landscape level

Intensive management based on clearcut harvesting is a major threat to forest biodiversity globally. However, it remains unclear how the long‐term accumulation of clearcuts at the landscape level affects biodiversity and what the maximum level of clearcutting that forest species can tolerate is, that is the safe operating space. We aim to evaluate the impact of the accumulation of clearcutting areas over time on bird communities in the intensively used forest landscapes of southern Finland and to define an ecological boundary for forest species in this region.

Based on the Finnish bird monitoring line transects (2006–2020), we related species richness and the abundance of the overall community and of species groups based on habitat affinity and Red List status with the accumulated area and mean size of clearcuts in the 5 and 20 years prior to bird observations. A trend analysis was conducted on a subset of transects with sufficient data to define a threshold of clearcut accumulation below which the abundance of forest species does not decline.

Clearcuts benefited open‐habitat species, including common farmland and mire threatened species. However, the 20‐year accumulation of clearcuts had negative impacts on common forest species and old‐growth forest specialists. The analyses of temporal trends showed that a maximum of 9.6% of the landscape should be clearcut in 10 years to maintain or allow the recovery of old‐growth forest specialists. Such a safe threshold corresponds to a rotation time of 91 years and indicates that at least 20% of forest areas should not be used in clearcutting management.

Synthesis and applications. Although clearcuts can benefit open‐habitat species, they should be limited to avoid declines in mature‐ and old‐forest species. By defining a safe limit in clearcut areas, we provide a readable target for ecologically sustainable forest use and a methodology that translates to other regions globally. However, such thresholds should be applied critically, as they are potentially context‐dependent and would require validation with multi‐taxa analyses.