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Death of bats at wind turbines disrupts natural food chains

The many victims of bats at wind turbines (WT) have a negative impact on the populations of affected species and potentially far-reaching consequences for biodiversity in rural areas. So far, it has only been possible to assume that the death of bats has had further consequences. Now a team of researchers from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) shows in an article in the scientific journal Conservation science and practice that natural food chains are broken, which can have far-reaching negative consequences for agriculture and forestry. The study shows the extent to which bats’ functional significance for habitats has been underestimated so far.

The researchers at Leibniz-IZW examined the exchange spectrum of the common nocturnal (Nyctalus noctula), a common bat species that often dies at wind turbines in Germany. By focusing on the insects that bats consume, they documented the extent to which their functional significance for habitats is lost.

Carolin Scholz and Christian Voigt from Leibniz-IZW investigated which insects ordinary noctules consumed shortly before they died at wind turbines. For this purpose, they analyzed the stomach contents of 17 common nocturias killed at wind turbines. Using PCR amplification and high throughput sequencing, the researchers searched for the genetic barcodes of the insects consumed by the bats. These genetic barcodes provide information about the identity of the species consumed. “We found DNA barcodes for 46 insect species from nine orders, most of them beetles and moths,” said Scholz, first author of the study. “Insect species can be assigned to a variety of habitats, from farmland and grassland to forests and wetlands.” Twenty percent of the identified insect species are considered pests or nuisances in agriculture and forestry, such as chestnut weevils (Curculio elephas) or the chestnut fruit stalk (Cydia splendana). The researchers conclude that the loss of bats disrupts existing food chains and can therefore lead to a higher number of pests and disturbing species, which can be compensated by chemical pest control. The free ecosystem service for reducing pest control by bats is reduced by wind turbines and is therefore an emerging problem for agriculture and forestry.

Energy production from wind power undoubtedly contributes to reducing CO2 emissions. In the end, the space required for this is large and the ecological side effects for affected animal groups such as bats and insects are enormous. Recently, it was decided to double the land used for wind energy production in Germany, especially on agricultural land and in forest monocultures. These ecosystems are already characterized by declining biodiversity, as they have undergone several waves of intensification in recent centuries, agricultural land has been cleared and cultivation methods against increased yields have been optimized. The WTs that are now being installed as part of the energy transition in Germany are driving a new wave of intensification.

“We are not aware of the consequences of this current intensification of land use for biodiversity and the resilience of these habitats. This is all the more regrettable as this transformation is currently taking place on a large scale in our landscapes,” reports Voigt, Head of the Department of Evolutionary Ecology. “We still need to understand in much more detail the effects of energy conversion on the biodiversity of these habitats. There is no doubt that the installed wind turbines contribute to the protection of the global climate and thus also to the conservation of biodiversity.” on the other hand, it is well known that large numbers of bats die at wind turbines. “The loss of these individuals is often difficult for populations to buffer, as the affected species have low reproduction rates. Unfortunately, not only do individuals disappear from the landscape, their interactions in complex food networks are also lost,” says Scholz.

Bills show that more than ten bats a year die at each conventionally powered wind turbine. This adds up to a six-figure number of annual bat deaths at the 30,000 wind turbines on the mainland in Germany. Newly installed turbines are temporarily shut down during periods of high bat activity to prevent bats from colliding with the rotor blades. This reduces bat mortality to one or two individuals per year and WT. Tragically, old WTs are still operated without such shutdown rules, and they make up 75% of all WTs in Germany. “We have to reckon with more than 200,000 bats a year dying of WTs,” says Voigt. “If we continue to tolerate this high number of victims at WTs, fewer and fewer pests will be consumed by bats,” he concludes. As predators, bats play an important role in the natural regulation of insect populations. The loss of bats and their role in food chains make ecosystems more vulnerable to disturbance, Voigt and Scholz speculate. More in-depth scientific work is needed to more accurately understand the food network links and the consequences of their outages. An important first step towards the conservation of bats and their functional role in their habitats must be a mandatory shutdown of wind turbines during periods of high bat activity, Voigt and Scholz demand. To this end, the approval practice for old wind turbines must be reconsidered. This is the only way to minimize the negative consequences of the intensified land use that energy conversion causes on our ecosystems.

Story source:

Material provided by Leibniz Institute for Zoo and Wildlife Research (IZW). Note! The content can be edited for style and length.

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