Barotrauma in Chiropterans: Pathophysiological Mechanisms and Implications for Conservation

Energy generated by wind farms is globally regarded as highly advantageous and classified as a “clean” and renewable source. However, at the local level, it is not always perceived as such. This is due to the considerable negative environmental impacts generated, which vary according to the characteristics of the location where wind farms are installed. This criticism becomes more significant when considering the inherent damage to biodiversity, especially to volant fauna. Among the principal environmental impacts reported are deforestation, soil erosion, noise pollution, magnetic interference, and population decline among this fauna, which includes insects, birds, and bats (Ferreira, 2019).

Attention to the impacts affecting bat species in Brazil emerged relatively recently, as the first Environmental Impact Assessment (EIA) studies involving animals affected by wind farms emphasized birds and flying insects as the principal taxa impacted. Approximately two decades later, studies concerning bat collisions with wind turbines began to emerge, and these are currently considered among the most significant environmental impacts associated with wind energy facilities (Sovernigo, 2009).

For chiropteran fauna, in addition to collision-related injuries (FIG. 1), the risk is intensified by another phenomenon: barotrauma. Bats are particularly vulnerable to this type of tissue injury, which is caused by a sudden drop in atmospheric pressure near the extremities of turbine blades. Although bats use echolocation to detect and avoid turbine blades, exposure to this air depressurization results in sudden pulmonary expansion, potentially leading to capillary rupture and internal hemorrhage (Barbosa Filho, 2013).

FIGURE 1: Radiographic image of a bat carcass (Eumops sp.) collected at a wind farm after death. Complete fractures of the clavicle and diaphyseal region of the humerus are evident, in addition to multiple fracture sites in the pelvis (arrows). Source: personal archive.

In this context, pathological analyses of bats found dead near wind energy facilities have demonstrated that barotrauma constitutes a significant cause of mortality in these animals. Microscopic examination of the lungs reveals the following principal findings: hemorrhage, edema, congestion, and embolism (FIG. 2). These lesions result from the sudden and violent expansion of the lungs in response to differences in air pressure, leading to rupture of alveolar walls and capillary vessels. The greater vulnerability of bats is associated with the high compliance and expansibility of mammalian lungs, physiological and anatomical characteristics determined by alveolar structure. However, this compliance also renders the lungs susceptible to overdistension and alveolar rupture when exposed to abrupt pressure variations. This characteristic contrasts with avian anatomy, as birds possess more rigid and robust lungs, which limits traumatic expansion and makes them significantly less susceptible to barotrauma (Rollins et al.)

FIGURE 2: Microscopic finding of an embolus (arrows) in a pulmonary artery of a silver-haired bat (Lasionycteris noctivagans). H&E staining (Hematoxylin and Eosin). Source: Rollins et al. (2012).

Findings regarding barotrauma in bats near wind farms are concerning for the regional conservation of bat populations. Unlike visible collision injuries, barotrauma represents a silent yet massive threat with direct and severe consequences for ecosystem health, given that chiropterans play an essential ecological role in biodiversity across multiple trophic levels. They act as pollinators of numerous plant species, seed dispersers, and controllers of insect populations (Staut, 2011).

To mitigate mortality caused by barotrauma and collisions, interventions should focus on operational adjustments and deterrent technologies. The most effective measure is increasing the cut-in speed of wind turbines, programming them to operate only under stronger wind conditions, when bat activity is reduced. Additionally, the installation of ultrasonic emitters on turbine blades acts as an acoustic deterrent, driving bats away from hazardous zones (Arnett et al., 2011). In Brazil, IBAMA and state environmental agencies regulate these activities through environmental licensing procedures and requirements for continuous wildlife monitoring. Research institutions complement these actions through pathological analyses that support the development of new conservation guidelines. Public participation occurs through support for sustainable energy policies that prioritize mitigation technologies while preserving the essential ecosystem services provided by chiropterans, such as pollination and pest control.

REFERÊNCIAS BIBLIOGRÁFICAS

ARNETT, E. B. et al. Altering turbine speed reduces bat mortality at wind-energy facilities. Frontiers in Ecology and the Environment, v. 9, n. 4, p. 209-214, 2011.

BARBOSA FILHO, W. P. Impactos Ambientais em Usinas Eólicas. AGRENER, GD. Itajubá –MG, 2013.

FERREIRA, J. M. Potenciais impactos ambientais de parques eólicos sobre morcegos no litoral sul do Rio Grande do Sul. In: CONGRESSO IBEAS, 2019. 

SOVERNIGO, M. H. Impacto dos aerogeradores sobre a avifauna e quiropterofauna no Brasil. Florianópolis: Universidade Federal de Santa Catarina, 2009. 

STAUT, F. O processo de implantação de parques eólicos no Nordeste brasileiro: aspectos ambientais e jurídicos. Salvador: Universidade Federal da Bahia, 2011. 

Rollins, K. E., D K Meyerholz, G D Johnson, A P Capparella, S S Loew “A Forensic Investigation into the Etiology of Bat Mortality at a Wind Farm: Barotrauma or Traumatic Injury?” Veterinary Pathology, 49:2, 2012, 362–371p.