Victoria will consider changing windfarm guidelines after government research found lifting the wind speed at which turbines start spinning could significantly reduce bat deaths without notably affecting the energy generated.
Ecologist Emma Bennett has estimated between 25,000 and 50,000 bats die annually from collisions with the about 2,300 wind turbines operating in Victoria.
Wind energy along Australia’s east coast kills an average of 12 bats per turbine each year, although rates vary depending on local conditions, consultants Symbolix found.
Australia has about 90 species of bats, ranging from megabats such as flying foxes (with up to a metre’s wingspan) to insect-eating microbats (some as small as a thumb, weighing less than a 10c coin). Thirteen are federally listed as threatened. Because bats are nocturnal and challenging to study, many bat species’ populations are unknown.
While some anti-renewable energy activists have sought to weaponise concerns about the impact of renewable energy on wildlife, researchers across government, universities and consulting firms have worked on potential solutions.
Researchers at the Victorian government’s Arthur Rylah Institute told an Ecological Society of Australia conference in Melbourne this week that collisions with turbines were a leading cause of bat deaths. Monitoring at Victorian windfarms indicated bats were killed “at a much higher rate” than birds. The institute’s Dr Lindy Lumsden said most deaths occurred during summer and autumn.
Dr Pia Lentini, also from the Arthur Rylah Institute, reviewed more than 500 studies between 2010 and 2024 examining bird and bat collisions and mitigation options. Curtailment was a “highly effective” measure that “significantly reduced” microbat fatalities across “every single study where they tested it”.
Most wind turbines “cut in”, or start turning, at wind speeds of about three metres a second (m/s), reaching maximum output at between 10 and 15m/s. Lifting the cut-in speed makes a difference because bat activity is generally higher at low wind speeds.
Lentini said studies from several countries – the US, Canada, Australia and Croatia – showed that increasing cut-in speeds by 1 to 3m/s reduced bat deaths by between 33% and 81%. Recent US research found a 5m/s cut-in speed reduced fatalities for all bats by nearly two-thirds.
A further study by the institute, which sought expert opinion, also concluded curtailment was the most effective approach for bats, compared with targeted wind turbine shutdowns, acoustic deterrents (where sound is broadcast to discourage animals from the turbine area) and habitat buffer zones.
Clean Energy Council senior policy officer Bronya Lipski said all windfarm developers were “keenly aware of the need to minimise impacts on bats” and already complied with “strict and detailed regulatory requirements”.
International research indicated curtailment could successfully reduce impacts for “some species of bats”, she said, but there were few Australian studies and none that had “studied curtailment on more modern, taller wind turbines”.
Lipski called for a coordinated, regional effort for ecological recovery that also addressed other key threats affecting bats, such as habitat loss and climate change. “Industry is required to avoid and minimise their particular impact but cannot be expected to single-handedly support species recovery when so many other threats are ignored.”
A Victorian government spokesperson said the new handbook – to be released for consultation soon – sought to “strike the right balance” between renewable energy and biodiversity.
“Building new renewable energy projects will deliver cheap and reliable power across the state and bring down emissions helping to protect our wildlife from climate change,” the spokesperson said.
Also at the conference, data scientists from Symbolix presented their first national estimates for bat fatalities associated with wind energy, based on analysis of more than 35,000 surveys at operating projects across Victoria, New South Wales and Queensland.
Statistician Alex Jackson said more details on species and benchmark models for data collection would be available after the analysis had been peer-reviewed and submitted for publication.
The Australasian Bat Society has called for “blanket curtailment to 7.0m/s at all turbines from dusk until dawn during months where bats are active” in the absence of site-specific collision risk data.
In a policy statement on wind energy, the organisation said it believed that provided steps were taken to avoid and minimise impacts, a viable wind industry could be established with no net loss to bat populations.
