A new study has determined that a significant number of bats are being killed by wind turbines in Germany — of which more than two-thirds of bats are in the process of migrating between their summer and winter habitats.
A number of studies investigating the effect of wind turbines on birds have found that the actual impact wind turbines have on avians is relatively low. However, according to this new research, published in the European Journal of Wildlife Research, wind turbines’ effects on bats — specifically in Germany — cannot be ignored.
As per the press release provided by Forschungsverbund Berlin e.V., “due to its geographical location in Europe, Germany has consequently a central responsibility for the conservation of migratory bats.”
According to the research (as per the press release), each wind turbine causes the death of approximately 10 to 12 bats per year if no mitigation measures are put in place. Naturally, these numbers vary based on geographical location and type, as well as the type of turbine.
However, according to the research, not many of these turbines are believed to have any mitigation measures. This led the researchers to conclude that if all the wind turbines in Germany were put into operation without any mitigation measures, nearly 250,000 bats would die per year. Of these numbers, approximately 70% can be attributed to bats migrating between summer and winter habitat.
“We assume that only a fractional part of all 24,000 wind turbines constructed until 2014 meet the necessary standards for the conservation of protected species,” said one of the report’s authors, Christian Voigt, biologist and bat researcher at the German Leibniz Institute for Zoo and Wildlife Research (IZW). “Many, especially old, turbines run without any or only insufficiently implemented mitigation measures.”
In reading the press release, however, one cannot help but notice a significant bias towards bats and against wind turbines.
“Not all things that are called “green” serve the purpose of nature conservation,” write the authors of the Forschungsverbund Berlin e.V. press release. They add that “many wind turbines are erected in Germany in order to increase the production of renewable energy by 30% until 2020. These turbines kill bats and are in conflict with national and international nature conservation legislation and international treaties such as the UN Convention on the Conservation of Migratory Species of Wild Animals”.
All of these things may be true, but as was the case for migratory birds and bird deaths at the hands of wind turbines, the whole story was often ignored in favor of sensationalizing out-of-context numbers.
Furthermore, further research found that wind turbines played a comparatively minor role in the death of birds when compared to other energy generation sources — for example, coal.
As can be seen in the above graph, courtesy of the U.S. News and World Report which took it upon itself to look at the numbers of birds killed each year by electricity sources in the US, the number of birds that meet their maker at the hands of wind turbines is comparatively small when compared to coal.
And of course, nothing comes anywhere close to causing bird deaths more than the cat, which on the whole manages to kill anywhere between 1.4 and 3.7 billion per year!
Finally, a study published at the end of 2014 showed that, in many cases, seabirds avoid collision with wind farms.
The above figure, courtesy of Desholm & Kahlert (2005), on Avian collision risk at an offshore wind farm. Biology Letters 1: 296-298, represents flight trajectories of migrating waterbirds within and outside an offshore wind farm.
Back to Bats
Finding similar research for bats is very difficult. News out of the Leibniz Institute for Zoo and Wildlife Research in August of 2014 showed that the migration of bats is thoroughly under-researched right now.
“Owing to decades of bird banding, ornithologists already know much about the migration of birds,” said Gunārs Pētersons, associate professor at the Latvian University for Agriculture. “However, the study of bat migration is still in its infancy. This is due to the fact that there are very few places worldwide where it is possible to observe and catch migrating bats in sufficient numbers.”
The only bat migration number I could find was out of Zambia, by way of travel website My Destination, which stated that visitors to the Kasanka National Park might have the chance to witness the “largest mammal migration in the world” — ie, the migration of 10 million fruit bats.
Using this as an outlier for bat migration numbers — a figure that I found virtually impossible to find for Europe, or Germany specifically — we can halve that and suggest that Europe might see a species of bat migration in the range of 3 to 5 million, which would put bat deaths at between 5 and 8.3% of the total number of bats migrating over Germany.
These numbers are highly speculative, but hopefully raises the fact that further questions need to be asked about this research: what percentage of bats migrating over Germany are actually dying as a result of wind turbines. Is it an excessive number? What legitimate mitigation can be implemented to bring these numbers down, regardless of percentages?
Wind turbines should not take precedence over wildlife conservation, but nor should wildlife conservation override any and all renewable energy development. Without a doubt, further research is necessary, and European wind development will need to begin integrating bat migration into their ecological assessment.