NOV 07, 2016 05:29 PM PST

Scientists still unsure of how wind farms impact bat fatalies


A new study released by a team of researchers from the United Kingdom in Cell Press journal Current Biology have determined that Environmental Impact Assessments, required by law for wind farms to complete before the construction of turbines, are not actually as effective as previously thought. Wind turbines pose a serious threat to many bat species which are protected by the Endangered Species Act, as a bat might be hit directly by the turbine or result in the animal’s bleeding lungs due to abrupt changes in air pressure around turbines. Protected by law, EIA’s for the bats’ well-being are mandatory for wind farm companies, and companies often spend a lot of money to go through with the EIA’s. But what is the system working?

"The findings highlight the difficulty of establishing with certainty the effect of major developments before they occur," says Fiona Mathews of the University of Exeter, UK. "This is a real problem for the planning system. In most countries, the system of Environmental Impact Assessment is based on the assumption that accurate assessment of risks can be made in advance and so appropriate steps [can be] taken to avoid any adverse effects—or if the bad effects cannot be mitigated, then the development should not be permitted to go ahead. Our work highlights that this can be difficult to achieve in practice, as animals do not always behave the way we might anticipate."

Mathews and her colleagues surveyed 46 wind farms across the UK for bat fatalities over the course of a month as part of a study to determine the impact of wind turbines on bats. Because it's extremely difficult to find dead bats, her team relied heavily on search dogs to locate casualties, she explains. They also used audio analysis to characterize bat activity.
 
Search dogs (including Ozzy, pictured here) helped researchers find tiny dead bats at wind farms. Credit: Victoria Stent
Therein that difficulty of finding dead bats lies another inherent problem of the system. EIA’s only require wind farm companies to complete the necessary pre-construction surveys, while mentioning nothing about post-development evaluation. "Failure to survey adequately [after construction] is a huge problem and explains why many wind farms apparently have 'no problem.'" The study reports that during their post-construction surveys, they found that half of the [18] sites contained casualties (ranging from one to 64 fatalities per month during the July–October survey period), and 97 percent had evidence of bat activity (ranging from one to 236 passes per night).

As scientists explain, the reason why wind farms are killing bats is an enigma. It might be that bats spot the tall towers and think they’re trees where they might find a meal or a place to rest or other bats. That’s a theory some biologists have because most of the fallen bats in the US are species that like to hang out in trees, Paul Cryan, a biologist with the United States Geological Survey in Fort Collins, Colorado states.
 

Nevertheless, the findings from the study are clear, says Matthews. "The precautionary principle indicates that sites perceived to contain little collision threat to bats should be treated with caution until there is a greater understanding of how to identify risk factors to bats," she writes. "On occasions when mitigation is currently deemed unnecessary, post-construction surveys should still be conducted (e.g. carcass searches) to ensure that the predictions are accurate and bat behaviour has not altered from pre-construction levels."

However, according to Mongabay, experts have come to understand that by turning the turbine blades away from the wind, a process called “feathering,” when bats are the most active during certain times of the year – often at night and in the summer - we can minimize the risk to bats. Typically, it’s not very windy at those times, so many times the operator may have disconnected the turbines from the power grid anyway, Mathews said. That could translate into a “win-win scenario,” she added. The operator wouldn’t be sacrificing much energy-generating potential while saving bat lives in the process.

Sources: Motherboard, Mongabay News, Phys
 
About the Author
  • Kathryn is a curious world-traveller interested in the intersection between nature, culture, history, and people. She has worked for environmental education non-profits and is a Spanish/English interpreter.
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