Worldwide, wind turbines are increasingly being built at forest sites to meet the goals of national climate strategies. Yet, the impact on forest ecosystems and biodiversity is barely understood. Bats may be heavily affected by wind turbines in forests, because many species depend on forest ecosystems for roosting and hunting and can experience high fatality rates at wind turbines.

We performed acoustic surveys in 24 temperate forests in the low mountain ranges of Central Germany to monitor changes in the acoustic activity of bats in relation to wind turbine proximity, rotor size, vegetation structure and season. Call sequences were identified and assigned to one of three functional guilds: open-space, edge-space and narrow-space foragers, the latter being mainly forest specialists.

Based on the response behaviour of bats towards wind turbines in open landscapes, we predicted decreasing bat activity towards wind turbines at forest sites, especially for narrow-space foragers.

Vertical vegetation heterogeneity had a strong positive effect on all bats, yet responses to wind turbines in forests varied across foraging guilds. Activity of narrow-space foragers decreased towards turbines over distances of several hundred meters, especially towards turbines with large rotors and during midsummer months. The activity of edge-space foragers did not change with distance to turbines or season, whereas the activity of open-space foragers increased close to turbines only in late summer.

Synthesis and applications: We show that narrow-space foragers avoid wind turbines in forests over a spatial scale of several hundred meters. This response was most apparent towards turbines with large rotors. Since forests are an important habitat for this guild, we advise to exclude forests with diverse vegetation structure as potential wind turbine sites and to consider compensation measures to account for habitat degradation associated with the operation of wind turbines in forests.

Please find detailed description of the methods in our paper.

README.txt - File can be opened with an text editor.

edge_space_foragers.xlsx,
narrow_space_foragers.xlsx,
open_space_foragers.xlsx - Files can be opened with Microsoft Word or open-source LibreOffice Writer.

Bat_Activity_Analysis.Rmd - File can be opened with Rstudio. R needs to be installed.