Wind turbines can indeed have negative impacts on some species of bats. One of the main concerns is collision risk, as bats can collide with the spinning blades of the turbines and be killed or injured. Another concern is habitat loss, as wind farms can sometimes be located in areas with significant bat habitats, leading to destruction or fragmentation of these habitats.
Several species of bats are considered to be threatened, including some that are particularly vulnerable to the impacts of wind turbines. For example, the hoary bat, the silver-haired bat, and the eastern red bat are all species that have been documented to be negatively affected by wind turbines.
Renewable energies, particularly wind power, are booming in order to meet climate protection goals. On the German mainland, over 30,000 turbines have already been installed, and the industry is currently scrambling to find increasingly scarce suitable sites. As a result, forests are becoming more prominent as potential sites.
In a new paper published in the scientific journal “Current Biology,” a scientific team from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) demonstrated that wind turbines in forests harm endangered bat species: Common noctules (Nyctalus noctula), a species that is at risk of colliding with rotor blades, are drawn to forest wind turbines if they are near their roosts. Far from roosts, common noctules avoid the turbines, essentially resulting in a loss of foraging space and thus habitat for this species.
The study’s findings show that wind turbines in forests harm common noctules in two ways: If wind turbines are built near roosts, noctules face an increased risk of colliding with the turbines, and they lose foraging habitat because they avoid wind turbines far from roosts. The team concludes in their paper that wind power development in forests should be avoided or, if necessary, undertaken with extreme caution. The wind turbine should be located at least 500 meters away from bat roosting sites, and any loss of foraging habitat should be compensated for by diverting forests from use for wind power (or other anthropogenic activities) elsewhere.
A large number of bat species occur in forests because there are many tree roosts and suitable foraging habitats with a high abundance of insects, their prey. These include species such as the common noctule, which is the most common victim among the bat species of wind turbines in Germany.
Christian Voigt
Wind energy production is an important pillar in Germany’s energy transition to renewable energies, and it contributes significantly to reducing greenhouse gas emissions. In Germany, approximately 8% of wind turbines have already been built in forests. This figure is expected to rise significantly in the coming years as suitable open-space sites become increasingly scarce.
“A large number of bat species occur in forests because there are many tree roosts and suitable foraging habitats with a high abundance of insects, their prey,” explains Christian Voigt, head of the Leibniz-Department IZW’s of Evolutionary Ecology.
“These include species such as the common noctule, which is the most common victim among the bat species of wind turbines in Germany. According to the German Federal Agency for Nature Conservation (BfN), common noctule populations are declining throughout Germany. It is therefore a matter of urgency to take a closer look at the interaction of bats with wind turbines in forests.”
Voigt and his colleagues used miniaturized GPS loggers to study the space-use behavior of common noctules. Over 1-2 nights, these loggers recorded the flight paths of 60 bats with high temporal and spatial resolution before automatically disconnecting from each animal.
“We discovered that common noctules were especially likely to approach wind turbines if they were located near bat roosts,” Voigt explains. Bats, as highly social mammals, use exposed structures as meeting places. If wind turbines are located near roosts, this could explain why they frequently approach wind turbines, which rise well above the canopy. The animals are at high risk of colliding with the rotor blades as a result of this.
“Wind turbines would therefore have to be erected at a sufficient distance from existing tree roosts,” concludes Christine Reusch, first author of the paper. “As roosts can also be newly created, there is a risk that supposedly safe wind turbines, which were initially erected at a sufficiently large distance from the then existing bat roosts during the approval phase, later become death traps,” Reusch adds.
The authors also found that further away from tree roosts, common noctules avoided wind turbines. They discovered this after they had carried out a data analysis in which all bat GPS locations in the vicinity of roosts were excluded from the analysis. This showed that bats avoid wind turbines if placed well beyond roosts. “This sounds like good news but it has a problematic side to it,” says Voigt. “Owing to their avoidance behaviour, common noctule bats essentially lose important hunting habitats.”
As a result, the scientists advise that wind turbines be avoided in forests, and that special precautions be taken if no other options are available. A minimum distance of 500 meters between wind turbines and known bat roosts should be considered during approval procedures, and the loss of foraging habitat in the vicinity of wind turbines should be compensated for elsewhere. According to Voigt and Reusch, the expansion of wind energy production into forests poses a significant conservation challenge because of the complex interaction of bats with wind turbines in forests.
Conservationists and wildlife managers are working to minimize the impacts of wind turbines on bats by developing strategies for siting turbines in areas that are less likely to be used by bats for foraging or migration, and by incorporating features into the design of the turbines that are intended to reduce the risk of collisions. For example, some wind farms are now being equipped with radar systems that can detect the presence of bats and automatically shut down the turbines when they are detected.
Overall, it’s important to consider the potential impacts of wind turbines on wildlife, including threatened species of bats, when evaluating the benefits and risks associated with renewable energy projects.
