Reducing Bat Fatalities at Wind Farms

As wind farms grow in popularity, there is also rising concern about wildlife fatalities. (Photo credit: Glen Allison/Photodisc/Getty Images

Energy generated by the wind is quickly becoming one of the fastest-growing sectors in the alternative-energy industry. Unlike fossil fuels, wind energy is renewable and emission-free. However, one downside to wind farms is that the turbines are responsible for a significant number of wildlife fatalities. Though bird deaths initially brought the first cause for concern, it has since been found that bat deaths greatly outweigh bird fatalities.

The majority of bat deaths occur between late August and early September, a time period that coincides with the migratory season for many tree-roosting bat species. In a study published in the Journal of Wildlife Management, researchers used thermal infrared cameras to capture video of bat flight behavior around wind turbines. Video evidence shows that bats actively forage around wind turbines and approached both moving and nonmoving turbine blades. The study authors hypothesize that bats may be attracted to the turbines by thinking that the structures are dead trees, and therefore a potential roosting place. The researchers also discovered that bats were more likely to be struck by turbine blades that were moving slowly; that is, in periods of low wind speed.

In another study published in the Journal of Wildlife Management, scientists found that bats are more likely to fly when wind speeds are low. They also noted a jump in bat fatalities in the time periods just before and just after a storm front passes through an area. The authors suggest that one way to prevent bat deaths would be to turn off wind turbines under certain weather conditions, particularly when bat activity in the area is high.

The tree-dwelling hoary bat is one species affected by wind turbine fatalities. (Photo credit: James Hager/Robert Harding World Imagery/Corbis)

The wind speed at which the blades of wind turbine begin to spin is called the cut-in speed. The majority of wind turbine blades are set to begin rotating as soon as wind speed reaches eight or nine miles per hour. Research published in Frontiers in Ecology and the Environment (a journal of the Ecological Society of America) indicates that raising the cut-in speed just a few miles per hour could significantly reduce bat fatalities. When the cut-in speed is raised to about 11 miles per hour, the researchers reported that bat deaths are reduced by at least 44 percent and up to 93 percent. In addition, they found that this raising the cut-in speed just a few miles per hour doesn’t affect energy production much–in fact, the wind farms experienced a decline in power production of less than one percent.

Given bats important roles as insect eaters, pollinators, and seed dispersers, it is important that their populations are protected. By implementing a simple change in the way power is generated at wind farms, bat fatalities may significantly be reduced and wind energy can maintain its environmentally-friendly reputation.

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