UMaine research finds new way to keep track of how land-based wind turbines impact bats

Generating renewable energy is important to meeting climate goals, but making sure that projects are planned in a way that is mindful of the environment is equally important. Research shows that measuring acoustic activity from bats might be the most efficient way to keep land-based wind energy turbines from killing the nocturnal creatures while getting the most energy possible out of the facilities. 

Many migratory tree-roosting bats die after coming in contact with spinning wind turbines at commercial renewable energy facilities in North America, particularly during the calm, warm late summer and fall nights when bats are most active. Preventing turbines from spinning when bats are active has been shown to reduce bat mortality rates, but this practice, known as curtailment, can reduce the amount of electricity generated so much that it is uneconomical for facility operators. 

Moreover, facility operators don’t know the site-specific relationship between bat activity and wind speed and temperature, and the method of hand-counting bat carcasses to estimate mortality rates is very labor-intensive and often imprecise.

A University of Maine-led study published in the Wildlife Society Bulletin looked at how effective acoustic detectors mounted on the turbines were at measuring risk to bats and designing site-specific curtailment strategies to minimize such risk. 

The researchers looked at two commercial wind energy facilities in West Virginia over the course of seven years. They paired acoustic monitoring of bat echolocation along with the wind speed and turbine speed, as well as manual counts of fresh bat carcasses. 

Although fatalities of 12 of 14 bat species that occur in West Virginia have been documented at wind energy facilities, three of the species — hoary bats, eastern red bats and silver-haired bats — accounted for 72% of the deaths in the region. 

The researchers found that bat activity while turbines were running explained around 80% of the variation in numbers of carcasses found at the facilities. Bat activity when turbines weren’t operating, though, had little or no relationship with fatality rates. 

“Acoustic detectors provide a window into the behavior of bats near turbines and provide critical feedback for measuring and managing mortality risk,” says Trevor Peterson, who conducted the research as a Ph.D. student in ecology and environmental sciences at the University of Maine and now works for Stantec Consulting Services Inc., in Topsham.

The results show that acoustic monitoring is an effective way to design, evaluate and manage strategies to protect bats from wind turbines while also achieving the most renewable energy production possible.

“When we understand the factors that influence the number of bats flying near turbines on a finer timescale, we can design smarter curtailment strategies that prevent turbine operation when bats are most active and allow for greater renewable energy generation during conditions with lower risk,” Peterson says. 

Contact: Sam Schipani, samantha.schipani@maine.edu