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Thursday, February 16, 2017
Wind Farms Kill 5 Million Bats Per Year
By Jack Dini @ 5:36 PM :: 6463 Views :: Energy, Environment

Wind Farms Killing of Bats in Hawaii and Elsewhere

by Jack Dini

Bats are known to be some of the world's savviest acrobats. Using their mysterious sonar system and shape shifting wings, bats adeptly swerve and swoop and dive in flight to avoid collisions with both stable and moving objects,. And yet bats stand no chance against a 200 meter high wind turbine with blades the length of a football field, spinning at speeds up to 275 km per hour. Even if their tiny bodies can avoid a blunt force collision with one of these merciless steel beasts, just the act of drawing near to a wind turbine may nonetheless expose bats to jarring air pressure changes that cause fatal lung damage reports Kenneth Richard. (1)

The slaughtering of bats by wind turbines isn't slowing down, it's getting worse. The 21st century bat killing has already begun to seriously threaten the long term survival of the world's 172 endangered bat species. According to scientists publishing in the journal Mammal Review, the spinning blades of wind turbines (together with white nose syndrome) are now the leading causes of multiple mortality events in bats. (2)

Hawaii's five major wind farms are killing endangered Hawaiian hoary bats at a much faster pace than expected. The wind farms have killed 146 Hawaiian hoary bats out of the 187 they are allowed. This in 6.4 years while they were expected not to reach the total for 20 years or more. (3)

A State Department of Land and Natural Resources Division of Forestry and wildlife report raises the question of how to balance protection of endangered species with the State's goal of producing more electricity from renewable sources and cutting Hawaii's dependence on imported fossil fuel.

Many of the wind farms are preparing to fund research that will help understand more about the bat populations and habitat use, which will enable the state to improve management and permit decisions. Also, a number of wind farms are trying various techniques to minimize bat deaths. (3)

So, how does Hawaii's issues with bats compare with the rest of the world?

The global scale slaughter of bats promises to get even worse in the coming few decades. In Canada alone, researchers have determined that an average of 15.5 bats are killed at each individual wind turbine site every year. At the 2013 installed wind capacity, 15.5 killings per turbine per year means that 47,400 bats are killed annually in Canada. With the 350% increase in installed wind capacity intended for Canada within the next 15 years, about 166,000 bats are projected to be slaughtered on a yearly basis by about 2030. (4)

Using the conservative determination of 15.5 bats killed per wind turbine, the 48,500 currently operating US wind turbines are now slaughtering over 750,000 bats per year. This bat killing rate appears to fall in line with other published estimates. For example, Hein and Schirmacher (2016) indicate that recent studies suggest US wind turbines were slaughtering between 600,000 and 880,000 bats per year as of 2012. (5)

Worldwide, 3 to 5 million bats are killed annually, reaching 10 million soon. As of 2015 there were 314,000 wind turbines spinning around the world and slaughtering bats by the millions. Using the conservative average of 15.5 bats killed per year by each wind turbine, it can be estimated that there are now 4.9 million bats slaughtered every year by the world's wind turbines. Even if the killing rate per individual wind turbine was generously reduced to ten bats per year instead of 15.5,wind turbine bat slaughter rates would still exceed 3 million per year.

Another serious problem for bats as mentioned earlier is white nose syndrome. Bat populations across North America and elsewhere have been plunging with the emergence of this fungal disease. Couple this with wind turbines and one can realize the seriousness of the bat problem. (6)

So how important are bats? They are a precious, but unheralded friend of farmers, providing consistent crop protection. Take away these colonies of pest killers and insect control costs would explode across farmlands. And just how much do bats save agriculture in pesticide use? Globally, the tally may reach a mind-numbing $53 billion per year according to researchers. A 2006 study proposed that bats save cotton growers $74 per acre in pesticide treatments across eight Texas counties. (7)

Clearly, bats are a valuable resource we cannot afford to lose.


1. Kenneth Richard, “Wind turbines now kill 3 to 5 million bats per year. And for what?”,, August 8, 2016

2. Thomes J. O'Shea et al., “Multiple mortality events in bats: a global review,” Mammal Review, 46, 175, July 2016

3. Kathryn Mykleseth, “Wind farms killing more bats than expected,” Honolulu Star Advertiser, January 14, 2017

4. J. Ryan Zimmerling and Charles M. Francis, “Bat mortality due to wind turbines in Canada,” The Journal of Wildlife Management, July 26, 2016

5. Chris D. Hein and Michael Schirmacher, “Impact of wind energy on bats: a summary of our current knowledge,” Human-Wildlife Interactions, 10(1): 19-27, Spring 2016

6. John Miner, “Wind turbines kill tens of thousands of bats including many on the endangered species list,” The London Free Press, July 20, 2016

7. Chris Bennett,”Bats save billions in pest control,”, August 4, 2016


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