Bat death on wind turbines: researchers warn of even worse consequences

The death of bats from wind turbines has consequences for food chains and biodiversity in rural areas. It could also have negative consequences for agriculture and forestry. This is the conclusion reached by scientists at the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) in Berlin. “The study demonstrates the extent to which the outstanding functional importance of bats for our habitats has been underestimated,” explains the IZW in a statement on the study, which was published in the journal Conservation Science and Practice.

The researchers at the IZW have been dealing with the death of bats on so-called wind turbines (WEA) for years. According to estimates from 2015, up to 250,000 animals have an accident in Germany every year on wind turbines that are operated without special protective measures. Conservationists say that pipistrelles, parti-colored bats, mosquito bats, pipistrelle bats and common noctule bats and noctule bats are particularly threatened. According to counts, more than ten bats are killed each year at each facility.

A study by the IZW from 2021 showed that in certain regions where pipistrelle bats breed, young bats in particular die. The animals crashed either through a direct collision with the rotating wings or through a so-called barotrauma in the air turbulence on the rotor blades, explained the researchers led by Christian Voigt, head of the Leibniz-IZW Department of Evolutionary Ecology and first author of the study. In addition, females in particular are attracted to new wind turbines – possibly when they are looking for new roosts.

Pest reduction will be compromised

So far, the IZW writes that it has only been possible to speculate about the further consequences of the death of bats. In the new study that has just been published, Carolin Scholz and Christian Voigt from the IZW Department of Evolutionary Ecology investigated which insects noctule bats consumed shortly before they died at the wind turbines. They analyzed the stomach contents of 17 animals. “Using sophisticated genetic methods, including high-throughput sequencing, they searched for the genetic barcodes of the eaten insects,” writes the IZW. These genetic barcodes provide information about the identity of the species.

“We found DNA barcodes from 46 insect species from nine orders, most of them beetles and moths,” says Carolin Scholz. “The insect species could be assigned to a large number of different habitats, from arable land to grassland to forests and wetlands.” Twenty percent of the identified insect species are regarded as pests or nuisances in agriculture and forestry, such as the sweet chestnut borer (Curculio elephas) ​​or the Oak moth (Cydia splendana).

The IZW research team concludes that the loss of bats disrupts existing food chains and that there could be a higher number of pests and pests, which could possibly be compensated for by chemical pest control. As hunters, bats play an important role in the natural regulation of insect populations. The free “service” of pest reduction by bats is affected by the wind turbines and is therefore a relevant topic for agriculture and forestry.

“We still need to understand much more precisely how the energy transition will affect biological diversity in the affected habitats,” says Christian Voigt. For him it is “out of the question” that wind turbines contribute to the protection of the global climate and thus also to the preservation of biodiversity. Biodiversity is threatened by drastic developments. In addition to climate change, this also includes the intensification of agriculture and forestry. The researchers around Voigt see the expansion of wind power as a new wave of intensification. They are concerned with reconciling both: the power of the wind and the protection of the bats.

Shutdown algorithm for wind turbines

Bats mostly fly at night, with weak winds and temperatures above ten degrees Celsius, say conservationists. Adjusting the operating hours of the wind turbines can significantly reduce the risk of collision. According to the IZW, systems are “meanwhile switched off temporarily at times of high bat activity to prevent the bats from colliding with the rotor blades”. This could reduce the number of victims to one or two individuals per year and system.

Among other things, there is the technical possibility of installing an automatic switch-off algorithm for wind turbines. For this purpose, bat activity at individual wind turbines is recorded for two years using an ultrasonic detector. A requirement that nature conservation authorities in Bavaria make when building wind turbines, for example. Tragically, however, old wind turbines are still being operated without shutdown rules, according to the IZW. That affects at least 75 percent of all systems in Germany.

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