Are wind turbines bat killers?

Batman has fought off the Joker, defeated the Penguin, dealt with Poison Ivy. Now, his newest enemy lies in wait, a merciless and bloodthirsty glint in his eye, for Batman and his little flappy friends.

The wind turbine. *dramatic music*

There’s been a slew headlines recently on the dangers wind turbines pose to bats. We tracked down two bat experts - Dr Paul Lintott from Exeter University, and Lia Gilmour from Bristol University. Both spend their time  researching human/animal interactions and conflict, and how we can live a bit more happily side by side. The picture they paint is far more complex than some headline grabbing horror stories. Their research shows there’s plenty that can be done to keep turbines turning and bats safe.

Bat deaths - the numbers

First of all, the bad news. How exactly do the bats die when they come into contact with wind turbines?

Lia Gilmour explains: “Bats are likely to be using turbines as an area to feed on their insect prey, which collect at these tall structures… Once in the rotor-sweep zone (the spinny bit) of a turbine, bats collide with the fast moving blades and usually die of traumatic injury or lung collapse due to pressure changes (barotrauma- although this is in a smaller number of cases).

Heartbreakingly, Lia suggests, bats may actually be attracted to turbines. There are a number of reasons for this she explains: “trying to roost, to interact with each other or because turbines make noises, though more work needs to be done in this area.”

How bats interact with wind turbines is a fairly new area of study. “It wasn’t until the early 2000s that people became aware that wind turbines potentially posed a collision threat to bats.” says Dr Lintott, and we had little idea of the scale of risk posed to bats in the UK. The University of Exeter decided it was worth getting some evidence, and started a research project in 2010. They wanted to know whether bats in Great Britain are being killed by wind turbines. It was the first time a national study like this had been conducted anywhere in the world.

The study looked at 46 different wind turbine sites in England, Wales and Scotland and researchers had the sad task of searching for bat bodies. They used their findings to work out how many bats were being killed per turbine, taking into account the bodies being eaten by predators, or the team not spotting them all. They found between 0 and 5.25 bats were killed per turbine, per month, although the numbers varied a lot in the different locations.

An over exaggeration?

But didn’t the Telegraph report much higher bat deaths? Back in November they reported on Dr Lintott’s studies with the headline: “Wind farms could be killing 80,000 bats a year, new study finds”.

For this paper, Dr Lintott and colleagues looked at 29 wind farms. “[W]e estimated that 194 bats were killed per month, with casualty rates varying from 1 to 64 per month across the sites.” So where does the 80,000 deaths come in?

“We’re not sure how they got to this figure.” says Dr Lintott. “They presumably extrapolated from our figure across all wind farms across the UK. However, as mortality varies considerably between sites, it is unreliable to simply extrapolate any results on a limited number of wind farms across all of the UK’s turbines.”

It wouldn’t be the first time the media has exaggerated the negatives of wind power. Last year 10:10 teamed up with Sandra Bernick from Imperial College to look at newspaper articles on wind power. She analysed comment pieces written between 2010 and 2016. Over half of the comment pieces were negative (52%) and only 17% positive. She also looked at what types of arguments were used for and against wind. Wind editorials tended to emphasise the risks with wind - for every four times a risk was raised, only one benefit was.

Making turbines safer

But papers exaggerating bat deaths,  doesn’t mean we can be complacent. Wind turbines do kill bats. So what’s being done to make clean energy safer?

Currently, wind farm developers have to fill in an Environmental Impact Assessment before they start building to estimate things like bat deaths. Dr Lintott’s research suggests there could be more useful ways to protect bats.

“We showed that expensive Ecological Impact Assessments (EIAs) carried out before wind farms were built often failed to accurately assess the true threat to bats.” Instead they suggest assessments after the farm’s been constructed, so problems can be identified early on and mitigated for.

And here’s the hopeful bit. There are lots of ways to do that, Dr Lintott says. “Bats are most active at night during the summer and early autumn. To reduce casualties, the rotation of turbines can be minimised at these times. Some operators are already adopting this approach to saving bats and we are currently testing how effective this is.”

“This approach obviously affects electricity generation, although to a lesser extent then you might imagine given that bats are at most risk during periods of low wind speeds in the summer: times when turbines are generating relatively little electricity.”

Lia Gilmour is also working on bat deterrence devices -  ways of keeping bats out of an area using (for example) high frequency speakers. “Preliminary data suggests that acoustic deterrents can reduce bat activity in foraging areas” she tells us, but is yet to be published. (watch this space!)

The bigger picture

Even with all this work, it’s important to keep things in perspective, says Dr Lintott. “Although bats are killed by wind turbines, it is important that this is put into context alongside the many other causes of bat mortality which are caused by humans.” Cars, cats and, of course, climate change.

And here lies the key message. As much as wind turbines pose some threat to bats, climate change is a much bigger problem. Many bat species are facing extinction from the impacts of climate change. Protecting the bats means we must do something about our carbon emissions - and cleaning up our energy supply is a key part of that.

Not only that, but wind turbines are actually much safer than the energy sources they are replacing. A 2009 study compared different types of power plants and found that fossil fuels resulted in 15 times more bird and bat deaths than wind turbines. So actually, building wind turbines is good for bats on two counts - turbines help us tackle climate change, and mean we use less of the dangerous-bat-killing fossil fuel power stations.

It’s a sad fact that wind turbines do kill bats. But it’s not fair to paint them as the next villain that Batman needs to destroy. There are plenty of ways we can make wind turbines safer for bats and research is finding new ways all the time. Bats are facing the same scary problems as the rest of us - climate change - and it’s in all our interests to do tackle it.

Thanks so much to Dr Paul Lintott and Lia Gilmour for taking to time to talk to us. If you’d like more info - you can read Dr Lintott’s paper if you’d like more info.


Photo: Pete Sheffield, creative commons