An investigation into the potential for wind turbines to cause barotrauma in bats

Abstract

The high rates of bat mortality caused by operating wind turbines is a concern for wind energy and wildlife stakeholders. One theory that explains the mortality is that bats are not only killed by impact trauma, but also by barotrauma that results from exposure to the pressure variations caused by rotating turbine blades. To date, no published research has calculated the pressure changes that bats may be exposed to when flying near wind turbines and then used these data to estimate the likelihood that turbines cause barotrauma in bats. To address this shortcoming, we performed computational fluid dynamics simulations of a wind turbine and analytical calculations of blade-tip vortices to estimate the characteristics of the sudden pressure changes bats may experience when flying near a utility-scale wind turbine. Because there are no data available that characterize the pressure changes that cause barotrauma in bats, we compared our results to changes in pressure levels that cause barotrauma and mortality in other mammals of similar size. This comparison shows that the magnitude of the low-pressures bats experience when flying near wind turbines is approximately 8 times smaller than the pressure that causes mortality in rats, the smallest mammal for which data are available. The magnitude of the high-pressures that bats may experience are approximately 80 times smaller than the exposure level that causes 50% mortality in mice, which have a body mass similar to several bat species that are killed by wind turbines. Further, our results show that for a bat to experience the largest possible magnitude of low- and high-pressures, they must take very specific and improbable flight paths that skim the surface of the blades. Even a small change in the flight path results in the bat being hit by the blade or experiencing a much smaller pressure change. Accordingly, if bats have a physiological response to rapid low- and high-pressure exposure that is similar to other mammals, we conclude that it is unlikely that barotrauma is responsible for a significant number of turbine-related bat fatalities, and that impact trauma is the likely cause of the majority of wind-turbine-related bat fatalities.

Offshore Occurrence of a Migratory Bat, Pipistrellus nathusii, Depends on Seasonality and Weather Conditions

“…At the same time, however, wind energy production causes biodiversity loss due to mortality, habitat loss, and barrier effects [ 1 , 2 ]. One of the major concerns is mortality amongst bats due to collisions and possibly barotrauma [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ], which affects both migratory and local populations [ 12 , 13 ]. For wind farms on land, it is estimated that 250,000 bats are likely killed annually in Germany [ 14 ], whilst 600,000 bat fatalities have been reported in the USA in one year [ 15 ].…”

Non-invasive sampling of bats reflects their potential as ecological indicators of heavy metal and trace metal contamination due to open cast diamond mining, northern Limpopo Province, South Africa

“…In addition to the global stressors that bats already face, namely habitat loss, changes in available resource quantity and quality, climate change, increasing number of wind turbines, disease pressure (de Souza et al 2020, Lawson et al 2020, Flache et al 2018, Hernout et al 2016a) and environmental pollution including organophosphates (Bayat et al 2014), it is vital that both the origin of elements and the toxicological response of bats is understood. This knowledge will assist conservation authorities and specialists to make informed decisions concerning bat conservation and mitigation strategies within the context of looming anthropogenic developments and conservation areas.…”

Non-invasive sampling of bats reflects their potential as ecological indicators of elemental exposure in a diamond mining area, northern Limpopo Province, South Africa

“…In addition to the global stressors that bats already face, namely habitat loss, changes in available resource quantity and quality, climate change, increasing number of wind turbines, disease pressure (Hernout et al 2016b ; Flache et al 2018 ; de Souza et al 2020 ; Lawson et al 2020 ) and environmental pollution including organophosphates (Bayat et al 2014 ), it is vital that both the origin of elements and the toxicological response of bats is understood. This knowledge will assist conservation authorities and specialists to make informed decisions concerning bat conservation and mitigation strategies within the context of looming anthropogenic developments and conservation areas.…”