Rewilding structural complexity: Responses of bats to active forest restoration

Restoring and protecting forests is essential to reverse biodiversity loss and to promote resilient, multifunctional ecosystems. However, it remains unclear whether active restoration measures can accelerate ecological recovery during the early stages of rewilding in newly protected forests. We investigated the response of forest-dwelling bats to a structural enhancement experiment established in mountainous spruce forest of the Black Forest National Park. On experimental plots, small groups of trees were toppled and ring-barked to increase structural heterogeneity, while adjacent control plots remained untreated. Forest structural changes were quantified using airborne LiDAR and digital orthophotos. Bat activity and community composition were surveyed on all experimental plots using automated acoustic recorders during repeated sampling campaigns in 2021 and 2023, corresponding to five and seven years after the experimental treatment. Bat activity and feeding activity were higher on enriched than on control plots, and differences between treatments increased with time. This response was primarily driven by edge- and open-space foraging bats, whereas narrow-space foragers responded more heterogeneously, with several Myotis species remaining associated with continuous forest cover. Structural enrichment of the forest also affected species composition. Our results demonstrate that targeted structural enrichment can accelerate ecological recovery during the early stages of forest restoration by promoting bat activity, foraging, and community turnover without reducing the occurrence of forest-specialist bats. Given the increasing vulnerability of spruce forests to climate change, active restoration can complement natural processes and contribute to biodiversity recovery, habitat heterogeneity, and the resilience of newly protected forests and multifunctional production landscapes.