Modelling the cumulative impact of wind farms on bats on a regional scale

Wind farms are steadily growing across Europe, with potentially detrimental effects on wildlife. When planning wind farm development on a regional scale, cumulative impacts besides local effects should be taken into account. Mapping the potential risk to bats on this scale would help large-scale planning of wind turbines and focus field surveys on more vulnerable areas. Although modelling offers a powerful approach to tackle this goal, its application has been so far neglected. To address this issue we developed a regional scale analysis based on Species Distribution Models (SDM) built on presence data in an area in central Italy that is currently undergoing a large-scale development of wind farms. We deliberately selected a regional rather than a national scale, since this is the geographical (and administrative) dimension at which wind farms development is planned and mitigation or compensation actions are done. Wind farms impacts were evaluated in terms of habitat alteration and barrier effect. In the first phase of the project we decided to test the functionality of our idea developing SDMs for two bat species particularly affected by wind turbines impact N. leisleri and P. pipistrellus and to investigate the landscape pattern alteration produced by wind farms. In a second phase encouraged by the results obtained for the two species we decided to investigate all the bat species present in the region particularly affected by wind turbinesN. Leisleri, P. Pipistrellus, P. Kuhlii, H. Savii, E. Serotinus, T. teniotisand to refine the SDMs considering environmental variables proxies for wind exposure and commuting ad migration routes. We were interested in highlighting the best areas for all the species potentially highly impacted by wind farms and to develop a species richness map useful to point out the hot spot of bat species in the region to identify the most risky area. With the SDMs developed in this second phase we also developed the first attempt to study the barrier effect through connectivity procedures. The specific objectives of our analysis were:a) to produce risk maps by overlaying the foraging habitat maps with existing and planned wind farms locations;b) to assess changes in the spatial pattern of foraging habitat determined by existing and planned wind turbines; c) to combine SDMs to identify highly vulnerable areas where wind farm construction would be especially harmful to bats and should be avoided. d) to investigate species specific connectivity and hot spot of migration routes e) to overlap corridors routes and wind farms. . SDMs were statistically robust (AUC? 0.8 for all species).Changes in landscape patterns consisted of a 7.7% increase in the number of patches and a 10.7% shape index increase and of a 8.1% decrease in the mean area of foraging habitat patches. Moreover, 21% of turbines were located within 150m from forest edges, increasing fatality risk. The region's western part, the hot spot of bat species in the region, needs careful consideration in future wind farm planning. We observed four main corridors routes for N. leisleri from the western part to the south-eastern part of the region. 14 existing and 6 planned wind farms impact both in term of landscape pattern alteration and barrier effect.At wind speed lower than 7 km/h existing turbines have to be shut down, and the construction of the 6 planned wind farms that fall in suitable areas and encounters high connectivity routes has to be avoided.