Bats About The Wind

Hello everyone!

With Halloween coming, you may be thinking of bats, so this post is about the impacts of wind farms on bats. Bats are affected significantly by wind turbines and many are found dead within wind farms. There are two main causes for bat fatalities and they are collision with the turbines (similar to birds) and barotrauma, which is when body tissue is harmed because of a very fast or very large change in air pressure. It’s kind of like when you’re in the plane and your ears feel blocked and you pop them but way worse for bats.

Bats which roost in trees could be more at risk in wind farms.
Photo by Vlad Kutepov on Unsplash

Bats are found to move towards wind turbines and one possible reason is that turbines look kind of like trees. A large proportion of bats which roost in trees and migrate were found dead in wind farms, which supports this hypothesis. This study found that bats tend are less likely to move towards wind turbines if the blades are spinning quickly and if the wind speed is high. This means that bats are more likely to hit the turbines at low wind speed, so raising the speed at which turbines start generating electricity could help to reduce the number of bat deaths. Turbine blades can also spin even if they aren’t generating energy, so it was found fewer bats died if the blades could be prevented from rotating at very low wind speeds. However, that could be a problem if we want to get as much use of the wind as possible, as lower cut-in speeds would help to increase the clean energy that we could get. On the other hand, since bats are an important part of ecosystems, we shouldn’t treat their deaths at the hands (blades?) of wind turbines lightly. After all, energy which harms animals isn’t clean.

The other reason for bat fatalities is barotrauma, where the bats can get serious internal injuries, especially in their respiratory system, if they fly near the spinning turbine blades. The anatomy of bats causes them to be extra vulnerable to the changes in air pressure, which results in barotrauma being responsible for many bat deaths in wind farms. Unfortunately, I couldn’t find solutions to prevent bats from flying near the blades so this is a big problem. I wonder if building a sort of fence/ cage around a turbine could prevent bats from being near to the turbines without affecting wind collected? Or would bats just fly into the cage and get hurt anyway if they cannot detect the cage? Hopefully, researchers will be able to figure out exactly why bats are attracted to wind turbines and find a way to stop it.

I hope this post has highlighted the dangers that wind farms pose to bats and that maybe someone will be able to figure out a better solution to prevent more bats from dying without affecting our green energy generation.

See you next week!

~Rayzel

5 Thoughts.

  1. Hi Rayzel

    Really intriguing post! I guess rather than attracting ‘moth to the flame’, it is ‘bat to the turbine’ in this case! Perhaps we have to devise or improvise on the designs of the turbine to make them less ‘fatal?’ to the bats.

    I was just curious, apart from the tree-resembling qualities and barotrauma, would the noise levels of a turbine somewhat affect bats, be it in a good way or bad way. As far as I know, modern turbines do not produce overly loud sounds but have characteristically systematic patterns (1). Do you think this might jeopardise a bat’s judgement as to whether the swinging blades are safe or dangerous, considering that bats aren’t really that affected by loud sounds (2)? Hope to hear your opinion on this one!

    (1) https://eng.mst.dk/air-noise-waste/noise/wind-turbines/noise-from-wind-turbines/#:~:text=Wind%20turbines%20emit%20a%20relatively,noise%20from%20the%20turbine%20machinery.

    (2) https://www.futurity.org/bats-sound-hearing-1128662-2/#:~:text=At%20some%20time%20or%20another,after%20the%20loud%20noise%20subsides.&text=Individual%20bats%20emit%20up%20to%20100%20to%20110%20decibels%20in%20sound%20pressure.,-The%20combined%20level

    • Hi Wen Han!
      I love that analogy and yes, I do think that we should find ways to change the wind turbines or maybe choosing wind farm locations more carefully so that there is less harm to animals. Unfortunately, I wasn’t able to find out if systematic noise patterns affect echolocation, but I did find out that rather than the loud sounds, it could be the very high pitched sounds aka ultrasounds that could cause some bats to avoid wind turbines. Since echolocation involves the use of ultrasounds, it is possible that it could cause them to avoid the turbine blades. This study found out that using ultrasound could help to reduce bat fatalities in wind farms, so I would say that rather than the noise level, it is the high frequency or pitch of the noise that could impair bat judgement. I’m not exactly sure how bats identify “danger”, but my guess is that the mental image (this article uses how we see things using our eyes and light as an analogy, but seismic sense from Avatar the Last Airbender is kind of how I imagine it) they form of the wind turbines could be very similar to that of trees which is why they don’t think that turbines are dangerous. I hope this answers your question and thank you for commenting!
      ~Rayzel

  2. Hi Rayzel,

    Very informative post !

    Something to bear in mind is that most bats killed at wind farm are migratory species. So, if we could greatly increase our knowledge of bat migration routes, that could help us do better when it comes to WHERE to place windfarms and what orientation the turbines should be set up on so that we avoid the problem in the first place.

    Of course, this wouldn’t necessarily account for the possibility that with climate change & habitat loss (or other pressures), bats may alter their migratory routes.

    And that’s where the lower cut-in speed comes in. Erin Baerwald was able to show that lowering it actually didn’t substantially affect the amount of energy produced or the income to wind farm companies because at low speeds, the turbines don’t produce that much electricity. But the reduction in bat fatalities when they did this experimentally was massive – if I recall, near 65 %.

    Now just think… wind energy is expanding in SE Asia, where there has been almost no research on fatalities of birds OR bats caused by wind turbines. And one of the world’s most important migratory routes (at least for birds), the East Asian-Australasian Flyway, passes right through our region. And it’s used by some of the world’s most critically endangered birds, such as the spoon-billed sandpiper. So… how much do you think we should place biodiversity at risk for the sake of expanding renewables ? What a dilemma !

    jc

    • Hi Dr Coleman!
      I did notice that most of the papers I found on bats and wind farms were in Europe or America, but now that I think about it, I don’t think I recall reading any in Asia. I read an article saying that Vietnam is aiming to increase power capacity through offshore wind farms, however, the article did not consider bats or birds. Since I believe that clean energy should also include other environmental impacts rather than just emissions or atmospheric pollutants, I think that increasing the use of wind energy or other renewables should not come at the cost of increasing biodiversity loss and this loss should be minimised as far as possible. I think it’s not fair to the plants and animals if we are already clearing the land to build wind farms or placing obstacles in their flight paths for the birds and bats. I hope that maybe more research on how to minimise these risks to biodiversity can be funded or more methods can be tested so that we don’t neglect both problems.
      ~Rayzel

  3. Great, we agree. Please consider advocating for additional investment into pre- and post-construction surveys for wind farms in SE Asia. This is, IMO, a critical research gap. And our research-priority-setting exercise, based on expert consensus, IDd it as such (Q81).
    https://www.sciencedirect.com/science/article/abs/pii/S0006320718315751
    Seriously, this could be a promising line of inquiry to consider after graduation if you continue to be interested in it.

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