Does the wind force endanger bats?

Up to a quarter of a million bats die in Germany through wind turbines

Wind Turbine in the USA © NREL / Iberdrola Renewables
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Wind turbines can turn into a death trap, and not only for birds: Bats are also losing their lives more and more often. According to new estimates, 600, 000 animals per year die in the US this way. In Germany, there are up to 250, 000, as researchers report in the journal "BioScience". But not all wind turbines are equally dangerous, their location is crucial.

A much discussed danger of wind farms is the bird strike. About 1, 000 birds, as estimated by the NABU in 2005, die each year due to a collision with the turbines. This figure is low compared to the fatalities caused by power lines and road traffic. But for another group of animals, the turbines are apparently deadly fatal: Bats are the circular rotor blades during the night hunting into the enclosure, especially during the time of their migrations in the summer. If they do not die by a direct collision, the turbulence and pressure drop behind the rotor blades can cause their internal organs to burst.

Number of victims varies by region

However, how many animals actually give their lives is difficult to say. Mark Hayes of the University of Colorado has now published a new extrapolation for the US. It is based on published datasets for 22 wind farms in the United States. Overall, Hayes estimates the number of animals killed annually in the US at 600, 000. This is a conservative value, as he emphasizes - partly because there are hardly any figures on wind farms in particularly high-flying states such as Texas, Arizona or New Mexico.

Bat (Corynorhinus townsendii) © Bureau of Land Management

The death toll varied widely across regions: in Harper County, Oklahoma, on average, only 0.5 bats lost their lives per megawatt of installed capacity. At Buffalo Mountain, Tennessee, this figure was 53.3. Hayes suspects that the location of wind farms plays a crucial role. "Locations near the Appalachians have the highest estimated mortality rates in this analysis, " he writes. "It is well known that bats make seasonal walks along mountain ranges."

The impact of wind power on the entire bat population is also difficult to say. The small, nocturnal animals are difficult to count. "In many cases, researchers would not even be able to pinpoint populations on a scale, " Hayes writes. What is certain, however, is that diseases such as the white nose syndrome additionally cause problems for the animals. As bat parents of many species raise only one cub each year, the animals are recovering very slowly from the consequences of such epidemics. display

Germany: 12 bats per plant

In Germany, too, the fatal relationship between bat and wind turbines attracts more and more attention. In August, researchers from the University of Leipzig published findings on 42 wind farms which they were, but kept them secret at the request of the operator. On average, twelve animals per plant died. Extrapolated to 25, 000 wind turbines in Germany, this would result in about a quarter of a million fatalities per year, and the trend is rising.

But the example from America shows that the number of killed bats depends heavily on the location of the wind farms. Extrapolations are therefore difficult. On the other hand, it is certain that more nocturnal journeyman would survive if the rotor blades rotated more slowly, at least at night or during the main pulling times. But less momentum means less electricity and thus less revenue for the energy producers. Looks like the bat urgently needs a strong lobby. (BioScience, 2013; doi: 10.1525 / bio.2013.63.12.10)

(American Institute of Biological Sciences, 11.11.2013 - NSC)