Migratory bat fatalities happen frequently at wind power plants, but the causes of deaths are not fully understood. Some research suggests that bats can’t react quickly enough to avoid fast-moving turbine blades, and that flying through varying air pressures created by the turbines can cause their internal organs to explode. Other research shows that plant operators can reduce bat fatalities by increasing the “cut-in” wind speed – the speed at which wind turbines are set to begin rotating and generating power. But few wind farms have enough information about bat migratory patterns to implement these strategies.
Part of the problem is that bat flight behavior is difficult to predict. Migratory patterns vary widely, depending on the time of year, and environmental conditions, including wind direction and speed, air temperature, and moon phase. Now researchers from the U.S. Forest Service’s Pacific Southwest Research Station (PSW) have developed an interactive tool that allows users to visualize how changes in date and weather conditions can increase or reduce the presence of bats. They hope that the tool can help wind energy facility operators make informed operational decisions that will help reduce the impact of wind turbines on migratory bats.
The research team used devices to monitor the echolocation calls of bats. Echolocation is the radar-like navigation system that bats use to detect objects in their flight path. The researchers compared the presence of bats to on-site weather conditions, and then built models to predict the presence of bats based on date and weather variables. The study was conducted at a wind energy facility in the San Gorgonio Pass Wind Resource Area near Palm Springs, Calif.
“Bat activity levels depend on more than just wind speed,” said ecologist Ted Weller, who led the research. “Our work demonstrates the use of a decision-making tool that could protect bats when fatality risk is highest while maximizing energy production on nights with a low chance of fatalities. Properly deployed echolocation monitoring can be an effective way to predict bat activity and, presumably, fatalities at wind energy facilities. These days, pre-construction echolocation monitoring is as common as meteorological monitoring at wind energy facilities, so the basic building blocks for these models are available at most proposed sites.”
The work was made possible by a collaboration between PSW, Iberdrola Renewables and the Bats and Wind Energy Cooperative, with funding from the California Energy Commission Public Interest Energy Research program. The interactive tool is available for download here. Findings from the study were published in the Journal of Wildlife Management. You can read the full article online here.