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Bat deaths caused by wind turbines disrupt natural food chains

A new study led by the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) has found that the numerous deaths of bats caused by wind turbines (WT) in Germany have a negative impact on the populations of affected species, as well as far-reaching consequences for the biodiversity of rural areas. According to the experts, since bats play an important role in the natural regulation of insect populations, their loss makes ecosystems more vulnerable to disturbances and has negative effects on agriculture and forestry. 

The researchers investigated the prey spectrum of the common noctule (Nyctalus noctula), a bat species that frequently dies at wind turbines in Germany. By analyzing the stomach content of 17 common noctules killed at wind turbines, they found DNA traces of 46 insect species from nine orders (most of them beetles and moths). Twenty percent of these insects – including, for example, the chestnut weevil (Curculio elephas) or the chestnut fruit moth (Cydia splendana) – are considered pests in agriculture and forestry. Thus, the loss of bats disrupts existing food chains and can lead to higher numbers of pests and nuisance species.

“We have to reckon with more than 200,000 bats per year dying at WTs,” said study co-author Christian Voigt, a wildlife biologist at Leibniz-IZW. “If we continue to tolerate this high number of victims at WTs, fewer and fewer insect pests will be consumed by bats.” 

While energy production from wind power indisputably contributes to reductions of greenhouse gas emissions, the disruptions to food-webs caused by bat casualties can have major, unpredictable ecological side-effects for a variety of animal species. “We do not know the consequences of this current land use intensification for biodiversity and the resilience of these habitats. This is all the more regrettable because this transformation is currently being carried out on a grand scale in our landscapes,” explained Dr. Voigt.

“We still need to understand in much greater detail which effects the energy transition has on the biological diversity in these habitats. There is no question that the installed wind turbines contribute to the protection of the global climate and thus also to the conservation of biodiversity.” 

However, according to study lead author Carolin Scholtz – a doctoral student in Ecological Dynamics at Leibniz-IZW – the numerous casualties of bats, “is often difficult for the 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 webs are also lost.”

According to the scientists, an important first step towards the conservation of bats and their crucial role in their habitats is the implementation of mandatory shutdowns of wind turbines during periods of high bat activity. Such actions would limit the negative consequences on ecosystems of the intensification of land use caused by the energy transition to wind power. 

The study is published in the journal Conservation Science and Practice.

By Andrei Ionescu, Staff Writer  

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