Report: Need for a database on bat activity on wind farms

A database on bat activity—and mortality—at wind farms in Poland is needed to minimize this phenomenon, say the authors of a report on the environmental aspects of wind farm development. They estimate that 6,000 bats die there annually. The industry assures that it is trying to address this.

The West Pomeranian University of Technology (ZUT) in Szczecin has prepared a document titled "Environmental Aspects of Onshore Wind Energy Development. Code of Good Practice." According to the authors, this is the result of updating the recommendations contained in previously used documents, which "no longer meet the current needs of society and nature."

The publication notes that in 2005, the total installed capacity of onshore wind energy was 123 MW. Currently, it has exceeded 10 GW.

The authors of the study noted that bats are a major problem in wind farm operation, and one of the most important outcomes of the code of good practices prepared by the West Pomeranian University of Technology (ZUT) would be a database containing information on bat mortality and activity at wind farms in Poland. The database would be managed by an independent institution.

"This is a major problem, similar to the impact of wind farms on birds, and sometimes even more so because bats are attracted to wind turbines. There are many locations where bat activity was previously low. After the wind turbines were erected, it turns out that this activity increases," noted Dr. Joanna Furmankiewicz from the University of Wrocław. She noted that this is likely because wind farms can provide good feeding and sheltering areas for bats.

"Bats either collide with the blades of a rotating fan, or by flying close to the fan's tip, they likely experience a pressure change, known as barotrauma," Furmankiewicz said. Barotrauma is a pressure injury that occurs as a result of a sudden change in pressure between the body's interior and its surroundings.

As Furmankiewicz noted, there is currently no comprehensive knowledge base in Poland regarding bat mortality and the factors that influence it. Knowledge is scattered, held by Regional Directorates for Environmental Protection (RDOŚ) or investors building wind farms.

"A nationwide database should be created to better manage the environment at wind farms. We will then be able to conduct analyses that will allow us (...) to develop, in collaboration with the investor, a flexible action plan to minimize bat mortality at wind farms," ​​Furmankiewicz noted.

In its study, the West Pomeranian University of Technology (ZUT) reported that data was obtained from the reports of the Regional Directorates for Environmental Protection for 126 wind farms with 1 to 53 turbines, totaling 1,333 wind turbines. A total of 1,649 dead bats were found at 657 of these, with the number of turbines with recorded mortality ranging from 1 to 337, depending on the species. The number of recorded fatalities per turbine ranged from 1 to 11, and bat mortality ranged from 0.03 to 6.33. The average mortality rate, calculated for all turbines and species, was 1.24.

The experts noted that in the reports for 24 out of 126 wind farms, no bats were recorded as collision victims, and in about half of the analysed wind farms, bat mortality was recorded at at least half of the turbines comprising a given farm during 2–3 years of post-investment monitoring.

The report's authors also cited data from the Institute for Renewable Energy. According to this data, as of November 2024, there were 1,441 wind farms connected to the power grid with a total capacity of 10,075 MW. Data available on the geoportal.gov.pl server from January 2025 indicates a total of over 5,100 wind turbines. "Considering the number of wind turbines currently operating in Poland and the data collected so far on bat mortality at Polish wind farms, and assuming that monitoring at other farms would be conducted over a similar timeframe, it can be estimated that at least 6,000 bats die at these farms annually," the report's authors stated, cautioning that these are conservative estimates.

Furmankiewicz pointed out that an analysis of the impact of wind farms on bat populations should encompass several criteria. "It would combine information, for example, about flight routes and wind directions, which are important for migrating bats," Furmankiewicz pointed out. She noted that the bat species that die near wind turbines are long-distance migrators. "Unfortunately, we don't yet know all the migration routes. And this is a very important issue to prevent bat mortality," she added.

Joanna Jakubicka, Environment and Biodiversity Manager at OX2 Polska, a company specializing in renewable energy investments, including the construction of onshore wind farms, emphasized that each wind farm construction is preceded by at least annual bat monitoring and the Regional Directorate for Environmental Protection (RDOŚ) defining the project's implementation conditions in an environmental decision. "Even at the planning stage of a wind farm, protection and the potential impact on bats are analyzed in detail, and if necessary, for example, the location of selected wind turbines is adjusted or mitigation measures are planned," she said.

She added that after the wind farm is built, environmental monitoring is resumed for at least three years and includes examining bat activity and mortality on the wind farm. "If a negative impact on bats is detected, additional mitigation measures are taken. These typically include shutting down wind turbines or increasing the turbine's start-up speed at night (during selected periods of peak activity under specific weather conditions)," Jakubicka said. She noted that the standard start-up speed of a wind turbine (the moment when the blades begin to rotate and produce energy) is typically 3-4 m/s. "Bats are most active at night at low wind speeds, specifically below 5-6 m/s. Therefore, to reduce bat-blade collisions, increasing the start-up speed at night is used," Jakubicka said.

She pointed out that new technologies are emerging, such as systems that detect bats approaching the turbine and shut it down during its flight, and ultrasonic bat-repelling systems. "It's important not to create landscape elements that are attractive to bats, such as tree lines or ponds, in the immediate vicinity of turbines," Jakubicka noted.

In her opinion, hanging bat boxes increases their chances of survival and reproduction. "OX2 has built a bat tower near the Kraśnik wind farm, which will provide shelter and enable the use of feeding grounds without the need to fly to distant colonies," she said. (PAP)

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