Last year, IEEE Spectrum profiled an ultrasonic alert for wind farm operators designed to let them know when bats are nearing their turbines. The potentially bat-saving technology can’t be ready soon enough according to this week’s issue of the journal Bioscience. University of Colorado ecologist Mark Hayes estimates that at least 600 000 and possibly more than 900 000 bats were killed by wind turbines last year in the U.S.
Hayes’ report is a statistical reassessment of data on bat carcasses found at wind turbine sites. His figure lends credence to a March 2013 mortality estimate of 880 000 deaths per year by Sacramento-based ornithologist and consultant Shawn Smallwood. That figure was well beyond previous estimates, which had ranged as low as 33 000. “My estimates, using different methods and data, bracket Smallwood’s 888 000 estimate,” writes Hayes in an e-mail to Spectrum.
He says his own estimates are likely conservative. That’s because he plugged in the lower figure for mortality at given turbine sites when those were reported as a range, and his estimate focuses only on migratory periods of the year.
Turbines are not the biggest problem facing bats, which are being decimated by White-nose Syndrome. Last year, the U.S. Fish and Wildlife Service estimated that the fungal disease had killed at least 5.7 to 6.7 million bats in 16 U.S. states and four Canadian provinces.
But while the White-nose mortality figure is cumulative—representing the total number of bats felled since the fungus was first recognized in 2006—Hayes’ figure suggests that turbines kill over half a million bats each year.
The system profiled by Spectrum last year aims to give wind farm operators the ability to ramp down turbines in order to protect bats—especially the most highly-endangered species. The acoustic system is designed to detect bat calls, identify the species, and then combine that information with meteorological data to determine the risk of bat collisions and, if appropriate, automatically idle nearby turbines.
No word yet from the Electric Power Research Institute on results from field tests of the system at wind farms in Wisconsin. But this April, Bedford, NH-based Normandeau Associates, the firm behind the technology, vowed to have it commercially available next year.
This post was created for Energywise, IEEE Spectrum’s blog on green power, cars and climate
Peter Fairley 
This estimate of 600,000 bats killed by US wind turbines is an interesting figure. I would guess there are something like 60,000 active wind turbines in the US — so about 10 bats per wind turbine. I wonder how this compares with the number of bats killed each year by other man-made obstacles like, cars, trains, airplanes, etc. Does this make wind turbines the number one man-made danger to bats, or does it rank low on the list? I just don’t have any perspective on this to know whether it would make sense to spend more money on each wind turbine to save 10 bats per year. Perhaps over 100 years bats that survive will pass along important genes to the population so that bats develop the skills to avoid wind turbines — evolution.
Wind turbines kill birds, too. But I am fairly certain glazing on tall buildings kill a lot more birds than do wind turbines — yet I don’t see cities passing legislation to require bird studies be conducted before erecting a building.