ScienceDaily (Sep. 28, 2009) — Scientists at the University of Calgary have found a way to reduce bat deaths from wind turbines by up to 60 percent without significantly reducing the energy generated from the wind farm. The research, recently published in the Journal of Wildlife Management, demonstrates that slowing turbine blades to near motionless in low-wind periods significantly reduces bat mortality.
"Biologically, this makes sense as bats are more likely to fly when wind speeds are relatively low. When it's really windy, which is when the turbines are reaping the most energy, bats don't like to fly. There is a potential for biology and economics to mesh nicely," says U of C biology professor Robert Barclay, who co-authored the paper with PhD student Erin Baerwald of the U of C as well as with Jason Edworthy and Matt Holder of TransAlta Corporation.
Last year, a groundbreaking Barclay-Baerwald study shed new light about the reasons for bat deaths under wind turbines in the Pincher Creek area. Researchers found that the majority of migratory bats in this southern Alberta location were killed because a sudden drop in air pressure near the blades caused injuries to the bats' lungs known as barotrauma. Although the respiratory systems in birds can withstand such drops, the physiology of bats' lungs does not allow for the sudden change of pressure.
Until recently, wildlife concerns regarding wind energy focused primarily on bird fatalities. But bat fatalities now outnumber those of birds due, in part, to efforts to mitigate bird deaths by wind turbines.
Most bats killed at wind energy facilities across North America are migratory tree bats, including hoary and silver-haired bats. The deaths occur during autumn migration from Canada and the Northern U.S. to the southern U.S. or Mexico.