Wind turbines too powerful for migrating bats

Not only birds fly south come autumn: in the last days of August, many millions of bats begin their southward journey from north-eastern Europe. As if obeying a secret commando, the bats set off on their migration, an event which remains relatively poorly studied. Some species, such as the 7 gram Nathusius’s pipistrelle, cover an annual distance of over 4000 kilometres. Yet for many hundreds of thousands of bats, this flight is one they won’t survive: they crash to the ground as they near wind power turbines.

“Bats can usually avoid the rotors thanks to their ultrasonic echolocation, but the vacuum created behind the wind turbines causes their lungs to explode,” says Prof. Dr. Fritz Vahrenholt, director of the German Wildlife Foundation. Experts call it barotrauma. The implications for bats are immense: in Germany alone, up to 240,000 bats die in wind turbines each year.

Shared airspace

Modern wind power turbines measure up to 200 metres, that’s taller than the Cologne Cathedral’s “mere” 158 metres. The up to 60 metre long rotor blades slice the sky on a surface of 10,000 square metres. The tips of the blades achieve the speed of a race car with 200 km/h. For bats, whose migratory flight altitude is the same as that of the rotor blades, these wind turbines present an insurmountable obstacle. They either die as a result of barotrauma or collide directly with the rotor blades.

Like a string of pearls

“In particular the states of Mecklenburg Vorpommern and Brandenburg have a special responsibility,” says Prof. Dr. Vahrenholt. “You just need to look at the map: wind power parks are lined up like a string of pearls from Frankfurt at the Oder to Rostock – and the bats leave their breeding sites in north-eastern Europe to fly south or west.”

Bats not the only endangered victims

Most indigenous bat species are on the Red List – and they are not the only victims. ”Next to bats, the wind turbines endanger wind-sensitive birds such as the extremely rare lesser spotted eagle, the black stork, and the red kite,” says Prof. Dr. Fritz Vahrenholt. He criticises that “wrong decisions in energy policy are difficult to revise later on.” For the director of the German Wildlife Foundation, one thing is clear: “Red-listed species and other indigenous wildlife should not be the victims of a premature energy policy.” The fast-paced species extinction and decline in biodiversity are unfortunately often downplayed and sacrificed in climate discussions.

Photo credit: imago stock&people

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