Better protection for bats

Researchers from Erlangen investigate ways of making wind farms more bat-friendly

Wind farms are generally considered a particularly environmentally friendly way of generating power. However, onshore wind farms can be a deadly threat to bats if the small mammals’ collide with the blades of the wind turbines. As part of a joint research project at the universities of Erlangen-Nuremberg and Hannover, ecologists, statisticians and engineers from Germany and Switzerland have now researched ways of reducing the risks to bats, which are now a protected species in Germany.

“Numerous studies in North America and Europe have shown that many wind farms can pose a risk to bats”, explains biologist Dr. Oliver Behr from the Friedrich-Alexander University of Erlangen-Nuremberg (FAU). “However, the risk varies greatly depending on the location of the plant. There are wind farms which appear harmless to bats and others where several dozen animals die per year.”

For their study, the researchers randomly selected 66 wind farms for closer observation located in different types of environment in the states of Brandenburg, Mecklenburg-Western Pomerania, Lower Saxony, Rhineland-Palatinate, Saarland, Saxony and Thuringia. To begin with, the researchers determined when and how often the bats stopped near the wind turbines. To do so, they attached acoustic detectors to the turbine rotors, which recorded the ultrasonic calls of the passing bats. The area at the foot of the tower was also searched for injured animals. The experts were able to find out from the results if the wind turbines’ height had an effect on the risk to bats, or if certain locations, for example those near woods, left more of the small mammals injured.

“Most animals died in the months of July and August – the months when the bats are particularly active around wind farms”, reported Dr. Oliver Behr. The researchers were also able to reveal that the small mammals are especially active during the first quarter of the night. Wind speeds strongly influence the animals’ activity: the more wind there is, the less bats there are.

These results allow us to analyse, in a more nuanced way, the potential difficulties facing the coexistence of wind farms and bats and to bring further plans for wind farm development into harmony with the protection of bats”, says Behr. If it becomes apparent that bats are in danger on a wind farm then future collisions could be avoided using a bat-friendly operation of the turbines adapted specifically to the site. The turbines will stop operating at times when especially high numbers of bats are flying around. As the animals are most active when wind speeds are low, the deactivation of plants occurs at times when less energy is being produced anyway. By doing so the operators can reduce the risks to bats and at the same time, keep revenue loss at a minimum.

The results of the study will be published in book form:
Robert Brinkmann, Oliver Behr, Ivo Niermann & Michael Reich (ed.): “Development of methods for the study and reduction of collision risks to bats at onshore wind farms” (in German), Cuvillier Verlag, Göttingen 2011, ISBN 978-3-86955-753-3, ISSN 2190-7161

Further information for the media:

uni | media service | research No. 31/2011 from 8.07.2011