In order to meet climate protection targets, renewable energies are booming, often wind power. More than 30,000 turbines have already been installed on the German mainland so far, and the industry is currently struggling to locate increasingly rare suitable sites. Therefore, forests are becoming potential locations. A scientific team from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) has now shown in a new article published in the scientific journal “Current Biology” that wind turbines in forests harm endangered bat species. extinction: common noctules (Nyctalus noctula), a species with a high risk of collision with rotor blades, are attracted to forest wind turbines if they are located near their roosts. Away from roosts, common noctules avoid turbines, essentially resulting in a loss of foraging space and thus habitat for this species.
The research results show that common noctules suffer in two ways from wind turbines in forests: if wind turbines are built close to roosts, noctules face an increased risk of colliding with the turbines and losing their feeding habitat because they avoid wind turbines far from roosting sites. . In their paper, the team concludes that wind power development in forests should be avoided or, if there is no alternative, undertaken with great care and caution. The wind turbine must be placed at least 500 meters away from bat roosting sites, and the loss of foraging habitat must be compensated by removing forests from wind energy use (or other anthropogenic activities) elsewhere.
Wind energy production is an important pillar for the energy transition towards renewable energy in Germany and contributes significantly to the reduction of greenhouse gas emissions. Approximately eight percent of the wind turbines in Germany have already been built in forests. This number is expected to increase significantly in the coming years as suitable sites in open landscapes become increasingly scarce. “A large number of bat species are found in forests because there are many tree shelters and suitable feeding habitats with a high abundance of insects, their prey,” says Christian Voigt, head of the Leibniz-IZW Department of Evolutionary Ecology. . “These include species such as the common noctule, which is the most common victim among bat species of wind turbines in Germany. According to the German Federal Agency for Nature Conservation (BfN), populations of common noctules are declining in all of Germany. Therefore, it is urgent to take a closer look at the interaction of bats with wind turbines in forests.”
Voigt and his colleagues investigated the space-use behavior of common noctules using miniaturized GPS loggers. These recorders recorded the flight paths of 60 bats at high temporal and spatial resolution for 1 to 2 nights before the recorders were automatically detached from each animal. “We found that common noctules were particularly likely to approach wind turbines if the latter were located near bat roosts,” explains Voigt. As highly social mammals, bats use exposed structures as meeting points. This could be why they often come close to wind turbines, which rise high above the canopy, if the turbines are located near roosts. This poses a high risk for the animals to collide with the rotor blades. “Wind turbines would therefore have to be erected at a sufficient distance from existing trees,” concludes Christine Reusch, first author of the article. “Since refuges can also be created anew, there is a risk that supposedly safe wind turbines, which were initially erected at a sufficiently large distance from the then-existing bat refuges during the approval phase, will later become into death traps,” adds Reusch.
The authors also found that further from tree roosts, common noctules avoided wind turbines. They discovered this after carrying out a data analysis in which all GPS locations of bats in the vicinity of roosts were excluded from the analysis. This showed that bats avoid wind turbines if they are positioned well beyond roosts. “This sounds like good news, but it has a troubling side,” says Voigt. “Because of their avoidance behavior, common nocturnal bats essentially lose important hunting habitats.” Therefore, scientists recommend, firstly, that wind turbines should not be located in forests and, secondly, that special care be taken if there are no alternatives. A minimum distance of 500 meters between wind turbines and known bat roosts should be taken into account during approval procedures and loss of feeding habitat in the vicinity of wind turbines elsewhere should be compensated for. Therefore, the expansion of wind energy production in forests is a major conservation challenge in view of the complex interaction of bats with wind turbines in forests, according to Voigt and Reusch.