Bats and Wind Turbines: Unlocking the Mystery of High Mortality

A Canadian researcher may have discovered why so many bats are killed by wind turbines. The number of bats felled by the machines is often four times as high as the number of birds, yet unlike birds, the dead bats rarely showed signs of external injury. In researching her master’s thesis, Erin Baerwald of the University of Calgary dissected 75 bats killed at wind farms and discovered that 69 showed a type of lung hemorrhaging, known as pulmonary barotrauma, caused by a sudden drop in air pressure. As a wind turbine’s blades spin, they lower air pressure, especially around the tip of the blades. Even though bats can detect the spinning blades with their radar, flying within a meter of the blades can rupture blood vessels in their lungs, according to Baerwald’s paper in Current Biology. Bat scientists say mortality can be reduced by building wind farms away from known migratory routes.