Most of us know that bats are flying mammals and some associate them with the myths of blood sucking. They are often small, similar in size to mice (about 10 cm), and are actually very sensitive to environmental changes. They are easily affected by insecticides, disturbance of the caves or the logging of trees they inhabit. Across Turkey and Europe every year, a significant number of bats are affected by wind farms.
One of the main issues is direct collision with the turbines. A secondary issue is even if no collision occurs, bats can be affected from the sudden change in the air pressure as the turbine operates, and end up with internal damage (called barotrauma), which usually results in death. These problems are further compounded with habitat disturbance and degradation effects. With their low reproductive rates, local bat populations might struggle to recover. To identify risks related to bats, we conduct bat surveys prior to the construction, to predict abundance and species diversity.
- Bats emit ultrasound calls, inaudible to us, for navigation (called the echolocation process). We employ special bat detectors to record their calls.
- We later analyse these recordings to identify species and gauge activity levels.
- We calculate Bat Activity Index (BAI) according to the acoustic analysis.
Some species of bats are low flyers and some are high flyers, and high flyers are often under the most collision risk. Specific regulations for the wind farm can become necessary when when increased levels of activity pertaining to high flyer bat species is encountered, or endangered species are detected. Most bat collisions are known to occur on low wind speeds and high temperatures. Mitigation action takes into account these environmental parameters and others, such as seasonality.
For wind farms already in operation, mortality studies are conducted to estimate the bat fatality as a result of collision.