Of Bats and Turbines
Activity of forest specialist bats decreases towards wind turbines at forest sites (2022) Ellerbrok et al., Journal of Applied Ecology, https://doi.org/10.1111/1365-2664.14249
Wind turbines are a constant source of controversy. The planet needs more renewable energy, yet wind turbines represent a threat to many bird populations. There have been a plethora of studies just in the last two years focussing on the impact of the turbines on birds. Yet furrier fliers often get overlooked, and it should come as no surprise that wind turbines can be a large source of mortality for bats as well.
Previously wind turbines were usually built out at sea, or in open, cleared land. Yet there has been a move over the last decade to building more wind turbines in forested areas. Moving further into forests could represent a larger threat for bats, so do they show any behaviour that could help them avoid wind turbines? That’s what today’s researchers wanted to find out.
What They Did
At 24 forests across southern Germany the team set up audio recording devices, placed at increasing distances from wind turbines. They recorded bat calls as a means of identifying the bats down to species, as well of measuring total activity around the turbine. The species were grouped into three different feeding guilds as well based on where the species of bats found their food: open-forest foragers, edge-space forages (bats who looked for food on the edges of clearings) and narrow.space foragers (bats who hunt in dense vegetation).
The team then looked at how the activity of the three types of bats changed as they got closer to the turbines. They also accounted for other factors, mainly based on the structure of the forest, to ensure they weren’t assuming relationships between bat activity and turbines that were actually just a product of the forest itself.
Did You Know: Are Turbines The Problem?
There’s a lot of work on how much of a problem wind turbines are for winged populations, and there’s generally two conclusions across the ecological community. 1) yes, wind turbines are a problem, but 2) they’re not one of the more pressing ones (one of the more pressing ones being climate change, which wind turbines are helping to fight against). We can do a lot more for bird and bat populations by simply keeping our cats inside than we can do protesting against wind farms.
What They Found
In total, the researchers recorded over 62,000 minutes of bat activity over 45 nights. The vast majority of these recordings were identified as edge foragers.
Somewhat unfortunately, for the majority of the bats (the open space and the edge foragers), bat activity was approximately the same close to the turbines as it was further away, potentially indicating that the bats just don’t avoid wind turbines. The activity of the narrow-space foragers did decrease closer to the turbines though, particularly closer to larger turbines (those with rotors over 93 metres in diameter).
As I’ve alluded to above, there was a massive imbalance in the minutes recorded for the three bat groups, with 83% of all recordings taken for edge foragers, and only 5% for the open space foragers. This doesn’t detract from the results, and it’s obviously not the researchers’ faults, but it does make the comparison between groups a little difficult.
We need to put more focus on bats when it comes to wind turbines! There has been plenty of focus on bird populations and potential mechanisms for helping birds avoid collisions with turbines, but precious little on our tiny mammalian friends. Integrating wind turbines with natural landscapes is going to be more and more necessary going forward, and making it easier for small mammals to avoid them should be a key research focus.
Dr. Sam Perrin is a freshwater ecologist who completed his PhD at the Norwegian University of Science and Technology who is currently sitting on an uncomfortably warm train wishing he could get some of this temperature acclimation he keeps reading about. You can read more about his research and the rest of the Ecology for the Masses writers here, see more of his work at Ecology for the Masses here, or follow him on Twitter here.