“Beware: exploding lungs” is not a sign one would expect to see at a wind farm. But a new study suggests this is the main reason bats die in large numbers around wind turbines.
The risk that wind turbines pose to birds is well known and has dogged debates over wind energy. In fact, several studies have suggested the risk to bats is greater. In May 2007, the US National Research Council published the results of a survey of US wind farms showing that two bat species accounted for 60% of winged animals killed. Migrating birds, meanwhile, appear to steer clear of the turbines.
Why bats – who echolocate moving objects – are killed by turbines has remained a mystery until now. The research council thought the high-frequency noise from the turbines’ gears and blades could be disrupting the bats’ echolocation systems.
In fact, a new study shows that the moving blades cause a drop in pressure that makes the delicate lungs of bats suddenly expand, bursting the tissue’s blood vessels. This is known as a barotrauma, and is well-known to scuba divers.
“While searching for bat carcasses under wind turbines, we noticed that many of the carcasses had no external injuries or no visible cause of death,” says Erin Baerwald of the University of Calgary in Canada.