Bats and Wind Turbines

Onshore wind farms have a complicated relationship with the natural world. They provide around 49% of the renewable energy in the UK and directly prevent the burning of fossil fuels that leads to further global warming [1]. While sustainable electricity generation is vital for moving towards a green future, bat and bird mortalities have increased as a result. Results show a high proportion of noctule and pipistrelle bat carcasses found at wind farm sites. With a careful assessment of new sites and mitigation measures, we can hope to limit the frequency of injury in aerial species.

The turbines themselves can cause direct mortalities through direct collision and barotrauma [2]. Barotrauma is an injury occurring from the reduced air pressure surrounding the turbine blades. While the majority of aerial species can detect and avoid a direct collision with the blades, there is no way for them to sense the change in the pressure surrounding the turbine. This means that if the animal has inhaled shortly before passing the turbine, the trapped air can damage their lungs and blood vessels [3].

Windfarm Wind Turbines - Free photo on Pixabay

Newly established wind farms may also disturb bird and bat populations through habitat loss and fragmentation. The sad truth is that while renewables are essential in the fight against anthropogenic climate change, they often have a larger land demand than oil energy generation [4]. It is vital that plans for wind farms are assessed against ecological risk and don’t intersect known migration routes. It is also vital that we utilize habitats that are degraded and avoid forest edges where many of our UK bat species frequent.

Some renewable energy suppliers are undertaking curtailment strategies to minimise bat fatalities. Research shows that bats are most active during nights with milder temperatures above 9.5oC and wind speeds below 6 m/s [4]. This means that turning turbines off at low wind speeds can prevent 90% of bat mortalities with relatively low yield loses [5]. While bats are a protected species in the UK, this curtailment strategy isn’t universal.

In contrast, a study by Law et al (2020) showed that wind farms presented a relative haven for reptile species such as adders, which are of high conservation importance. Wind farms represent an area where adders are free from predation by birds. These sites could potentially be utilized for reptile reintroduction programmes as the lack of predation would increase the survival of the newly introduced population [4].

Going forward we must balance human requirement for energy generation with wildlife conservation goals and prioritise the species most at risk. In surveys of the general public, threat to wildlife was highly rated as a driver of local opposition to wind farms, so work into minimising this impact would help increase community acceptance of these projects [7]. The Bat Conservation Trust is currently working to produce guidance for wind farms on protecting bats. This guidance will include surveying and impact assessment, mitigation and bat monitoring [2].

[3] Baerwald, E. F. et al. (2008) ‘Barotrauma is a significant cause of bat fatalities at wind turbines’, Current Biology. Cell Press, pp. R695–R696. doi: 10.1016/j.cub.2008.06.029.
[4] Law, C., Lancaster, L., Hall, J. et al. Quantifying the differences in avian attack rates on reptiles between an infrastructure and a control site. Eur J Wildl Res 66, 54 (2020).
[5] Colleen M. Martin, Edward B. Arnett, Richard D. Stevens, Mark C. Wallace, Reducing bat fatalities at wind facilities while improving the economic efficiency of operational mitigation, Journal of Mammalogy, Volume 98, Issue 2, 21 March 2017, Pages 378–385,
[6] Robson, 2020. Patterns of Bat Activity at Upland Wind farms. CIEEM Webinar
[7] Klain et al, 2018. Bird Killer, Industrial Intruder or Clean Energy? Perceiving Risks to Ecosystem Services Due to an Offshore Wind Farm. Ecological economics. Volume 143, January 2018, Pages 111-129