2025

Meramo, Katarina; Vasko, Ville Veijo Wilhelm; Pietikäinen, Tia-Marie; Laine, Veronika; Ovaskainen, Otso; Lilley, Thomas M.

Context Given the rate at which humankind is changing habitats, it is essential to understand its impact on the surrounding nature and biota. The intensification of human activities and the fragmentation of forested habitats now affect many taxonomic groups, such as bats, which are largely dependent on forests (e.g. roosting sites and feeding areas). Northern Europe is generally considered very forested but intensive land-use changes, caused by urbanization and forestry, contribute to forest fragmentation and loss of biodiversity. Land-use changes are classified as the biggest threats for bats, but especially in the boreal zone, the impact of these environmental changes is not yet known at a sufficient level. Objectives We explored how bats (species occurrences and activity) were influenced by forestry and urbanization, and by landscape variables (tree volume, percentage of deciduous trees, vicinity of water bodies and built areas). Methods We used a bioacoustic dataset on bats from Finnish capital area (20 × 20 km, 51 sites) recorded during the summer season (May – September) to evaluate how different habitat classes (old forest, young economical forest, rural area, suburban and urban) and landscape variables influence activity and species richness of bats across this region. We used Hierarchical Modelling of Species Communities (HMSC) approach to characterize the responses of species. We investigated with two different models: one focusing on species occurrences and the second one focusing on relative activity. Results Our findings indicate a distinct pattern, with the highest species richness in old forests, followed by a gradual decline with increased land-use intensity. Species-specific responses to habitat classes were evident in both presence and activity. Most of the species showed negative responses to built area, either by their presence or activity. Key landscape variables further underscored species-specific variations in different environmental conditions. Additionally, our study observed temporal dynamics, revealing species-specific variations in occurrences across the bats’ active season. Conclusion Our study sheds light on the complex dynamics of bats in diverse landscapes, emphasizing the crucial role of both habitats and specific environmental factors in conservation. Old natural forests emerge as vital for bats, while land-use changes, especially urbanization, pose challenges highlighting the need for continuous monitoring and strategic conservation actions.