Targeted marking of wind turbines can protect bats

Every year in Germany, "200.000 bats are killed because of wind turbines," Fabien Verniest, a postdoctoral researcher at the National Museum of Natural History and lead co-author of a study on bats and wind turbines, published Wednesday in the Journal of Applied Ecology, told AFP.

"Wind turbines pose a threat in two ways. The first, the most well-known to the general public and the most studied in scientific literature, is the risk of collision," explains Mr. Verniest. "This risk particularly concerns high-flying species, such as noctule bats, which fly at rotor height."

The reasons why bats approach wind turbines remain unknown.

"They are sensitive to light pollution, and we are thinking about the particular role of aeronautical lighting of wind turbines in this process of attraction and repulsion," says Fabien Verniest.

The disturbances caused by air masses disrupted by wind turbines can also lead them to believe they are encountering "large trees, places for breeding, resting, or even mating." And since insects are also attracted to wind turbines, bats may try to approach them to feed.

The second threat concerns their disrupted habitat. Because of the presence of wind turbines, "some tree-dwelling bats prefer to settle in buildings (houses, barns) rather than in trees."

Transponders

Gaëlle Larnoy, the main co-author who was doing her Master2 internship, and Fabien Verniest therefore decided to go to the wind farms in Northeast Germany to find a solution.

Why there? "Because at that time, in 2021, there was a type of signage that we call circumstantial which was being tested in one of the parks," explains Fabien Verniest.

Contextualized marking is a type of aeronautical lighting which, instead of being activated continuously throughout the night, is only activated when an aircraft approaches.

"These are lights that emit high-intensity red flashes in all directions and are positioned at the top of the gondolas. We can see them for several kilometers, even when we drive on the highway," explains the researcher.

Since then, detailed signage has become mandatory in Germany. In France, only continuous signage is permitted.

"We measured the acoustic activity of bats using a recorder that captures ultrasound. And we compared this activity to those recorded when there is specific marking, marking all night, or on control sites without wind turbines."

The researchers established that activity near wind turbines with circumstantial marking "was lower than that measured at wind turbines with continuous marking and similar to that of control sites without wind turbines".

This means that continuous marking helps attract bats.

"The specific marking helps to limit this behavior, and therefore potentially to limit the risks of collision," the researcher concludes.

In France, to change regulations and authorize specific markings, it would be necessary to obtain the approval of the Ministry of the Armed Forces.

"To detect aircraft approaching wind farms, most of these detailed markings use transponders that equip all aircraft. And for obvious safety reasons, the Ministry of the Armed Forces does not wish to equip its aircraft with transponders," notes Fabien Verniest.