Pre-regulation wind turbines may cause substantial bat mortality

Based on a small-scale survey, the researchers estimate that bat fatalities (killed bats) across the country could exceed 200 000 per year. The researchers argue that these annual losses of bats are likely to eventually lead to a decline of the populations of the species at high risk of collision. Therefore, they recommend a review of old facilities and the adoption of appropriate mitigation measures in facilities that still operate without these initiatives, or a cessation of operations if high impacts cannot be effectively mitigated.

The installation of wind turbines for renewable energy generation has proliferated across Europe since the start of the 21^st Century. All European bat species are protected under the EU Habitats Directive¹, and collisions with turbines have been reported since the early 2000s.

Some European countries, including Germany, have mandated mitigation measures since around 2010. These typically include risk assessments at site-selection stage and operating restrictions, for instance preventing the rotor from turning during high-risk periods, such as migration seasons, or in weather conditions in which bats are most active. However, in Germany, the turbines installed before regulations came into force continue to operate without mitigation. This study assessed the potential impact of such old facilities on bat populations.

The researchers conducted field work at a site about 50 kilometres west of Berlin containing three 1.8-megawatt wind turbines installed before regulations took effect. They conducted 17 searches for bat carcasses within a 50-metre radius of each turbine during August and September 2021 – a key bat migration season. They estimated the number of bat carcasses that would have been missed or removed by scavengers between the searches, and used a software package to approximate the total number of bat fatalities that would have led to the number of bat carcasses that were observed. They also collected information on bat carcasses found at the site between 2001 and 2021 (including their survey).

The researchers report that 88 bat carcasses had been recorded at this site over the 20-year period, of which 38 were pipistrelles (Pipistrellus spp.), 24 were noctules (Nyctalus spp.), two were other identified species and 24 had not been identified. They say that 95% of these were found during migration periods in May and July to September.

In the 2021 survey of the site, the researchers found 18 bat carcasses, composed of 15 pipistrelles and three noctules. They say that, accounting for carcasses that would have been missed in searches or removed by scavengers, this suggests there were approximately 209 bat fatalities over the two-month period – equivalent to nearly 70 per turbine. They highlight that the study period did not cover the entirety of the migration season and suggest that the annual fatality level may be substantially higher. They also note that this two-month figure is much greater than existing annual bat-fatality estimates which they report as being in the range of 1 to 30 and averaging at 14.3 per turbine, based on published studies².

The researchers argue that the siting of the park, presumed not to have considered bat-migration routes, and the lack of restrictions have led to high levels of bat fatalities. They estimate that, as of 2021, there are at least 20 000 pre-regulation turbines operating in Germany and suggest that these could be killing over 200 000 bats each year. They highlight that bats are slow-reproducing animals and populations take time to recover from losses. They also note that losses suffered during migration may only be detected at a significant distance from the fatality site, if at all. They add that it is unclear whether such fatalities have already had a significant effect on regional bat populations.

The researchers note that, while some countries in Europe require mitigation measures for new wind turbines, such as those detailed in the UNEP/EUROBATS publication ‘Guidelines for consideration of bats in wind-farm projects’³, many do not. They suggest that there should be reviews of old wind turbines operating in high-risk sites without restrictions – with the aim of creating mitigation measures or, if necessary, decommissioning.

1. Barova, S. and Streoit, A. (2018) ‘Action Plan for the Conservation of All Bat Species in the European Union 2018 – 2024’. European Commission. Available from: https://ec.europa.eu/environment/nature/conservation/species/action_plans/pdf/EU%20Bats%20Action%20Plan.pdf  [Accessed 16 November 2022]
2. For example, Măntoiu, D.S., Kravchenko, K., Lehnert, L.S. et. al. (2020). Wildlife and infrastructure: impact of wind turbines on bats in the Black Sea coast region. Eur. J. Wildl. Res. 66 (3), 1–13.
3. Rodrigues, L., Bach, L., Dubourg-Savage, M.-J., Karapandža, B., Rnjak, D., Kervyn, T. Dekker, J., Kepel, A., Bach, P., Collins, J., Harbusch, C., Park, K. Micevski, B., and Minderman, J. (2015) Guidelines for consideration of bats in wind farm projects – Revision 2014. EUROBATS Publication Series No. 6, EUROBATS Secretariat, Bonn, Germany. Available from: EUROBATS_6_wind turbines_engl_web_neu.pdf [Accessed 20 December 2022]

Source:

Voigt, C. C., Kaiser, K., Look, S., Scharnweber, K. and Scholz, C. (2022) Wind turbines without curtailment produce large numbers of bat fatalities throughout their lifetime: A call against ignorance and neglect. Global Ecology and Conservation 37: e02149. Available from: https://doi.org/10.1016/j.gecco.2022.e02149

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“Science for Environment Policy”: European Commission DG Environment News Alert Service, edited by the Science Communication Unit, The University of the West of England, Bristol.

Notes on content:

The contents and views included in Science for Environment Policy are based on independent, peer reviewed research and do not necessarily reflect the position of the European Commission. Please note that this article is a summary of only one study. Other studies may come to other conclusions.