Tag: Bats

Research Identifies Measures to Reduce Wind Energy-related Bird and Bat Fatalities

Research Identifies Measures to Reduce Wind Energy-related Bird and Bat Fatalities

Brad Trumbo

Published July 7th 2023 at Harvesting Nature

Wind energy production facilities have been condemned for impacts to bird and bat species, but recent research suggests that minimizing impacts while maintaining power production efficiency may be feasible.

Wind energy production facilities are increasingly common worldwide, resulting from efforts to shift to renewable energy sources – a trend that will likely continue in the US. In 2022, President Biden invoked the Defense Production Act to allow the U.S. to “take ownership of its clean energy independence[1].”

The purpose for calling upon this decades-old act is to provide the US Department of Energy the authority to “help strengthen domestic solar, heat pump, and grid manufacturing industries while fortifying America’s economic security and creating good-paying jobs, and lowering utility costs along the way.” Invocation of the Defense Production Act is anticipated to “boost American production of the critical technologies necessary to lower energy costs, support the clean energy economy, and strengthen national security.”

In 2021, Princeton University estimated that the US would need to develop 19-96 gigawatts of wind energy production each year to reach “net-zero” greenhouse gas emissions by 2050[2]. And, like most energy production sources, wind turbines are known to impact wildlife, namely a proportion of birds and bats that encounter them. Therefore, the May/June 2023 issue of The Wildlife Professional provides a timely summary of potential measures to reduce bird and bat mortality at wind turbines2.  

Organizations like the US Fish and Wildlife Service have developed guidelines for wind turbine operations to minimize impacts on birds and bats through a process called “curtailment.” For example, bats are more active around wind turbines operating at slower speeds, so a curtailment measure would be to set a higher windspeed threshold (i.e. “cut-in speed”) for which the wind turbine would begin to operate. Research has shown that cut-in windspeeds between 11-15 miles per hour reduce bat fatalities by up to 63 percent[3], and curtailment to over 16 miles per hour reduces fatalities by over 80 percent for some species[4]. Curtailment has also been found to reduce eagle fatalities on par with bats.

A 60 to 80 percent reduction in bat and eagle mortality seems to support implementing curtailment measures, but curtailment reduces power production efficiency for facilities that some would argue are inefficient even without operating restrictions. For this reason, additional actions are being evaluated.

A global positioning system (GPS)-triggered “geo-fence” is being implemented with California condors. When a tagged condor enters the defined perimeter of a wind facility, the tag detection triggers immediate curtailment measures and avoids wind turbines operating under curtailment when no birds are present. This is an effective method of reducing condor fatalities, but tagging individuals is not a feasible solution for songbirds and bats. Deterrent strategies may be more effective.

Deterrents that have been studied reduce bird and bat mortality without impacting power production and include sound, high-contrast lighting, and painted turbine blades to avoid the appearance of blurring together at high speed. Only auditory deterrents are effective for bats, and each species’ use of echolocation differs, making one-size-fits-all deterrents less effective.

No single fatality reduction measure has proven effective for all species; however, a combination of deterrents and curtailment may be tailored to facilities, and research is ongoing to identify additional measures to reduce bird and bat fatalities while allowing efficient wind energy production.

[1] President Biden Invokes Defense Production Act | Department of Energy

[2] Felton, S. 2023. Change in the Air: Technological Solutions can Reduce Bird and Bat Collisions at Wind Facilities. The Wildlife Professional 17(3):38-40.

[3] A review of the effectiveness of operational curtailment for reducing bat fatalities at terrestrial wind farms in North America | PLOS ONE

[4] A smart curtailment approach for reducing bat fatalities and curtailment time at wind energy facilities – PubMed (nih.gov)

Northern Long-eared Bats Survive White-nose Syndrome in Man-made Habitats

Northern Long-eared Bats Survive White-nose Syndrome in Man-made Habitats

Brad Trumbo

Published in August 2021 @HarvestingNature

Since its first identification in a cave in New York in 2006, white-nose syndrome (WNS) in bats has caused significant population declines. White-nose syndrome is caused by a fungus, Pseudogymnoascus destructans, that infects the skin of the muzzle, ears, and wings of hibernating bat species across 35 states and seven Canadian provinces at present[1]. The fungus thrives in cold, damp conditions, perfectly suited for winter cave hibernacula. As it grows, the fungus causes changes in hibernating bats that make them become more active than usual and burn fat they need to survive the winter[2].

Northern long-eared bats (Nyctophilus arnhemensis) suffered a 95 percent population decline in New England between 2006-2012 due to WNS, and are now listed as “threatened” under the Endangered Species Act. Similar declines have been document in the little brown bat (Myotis lucifugus), among others.

While studying WNS and bats in their winter hibernacula, researchers tracked a small number of bats hibernating in home crawl spaces, basements, and other structures like concrete culverts in Martha’s Vineyard, Nantucket, and Long Island, New York. Luanne Johnson with Biodiversity Works reported that these bats were surviving the winter even when affected by WNS.

Crawl-spaces with dirt floors and homes with block foundations and BILCO style hatch doors are attractive bat hibernacula. Uninsulated foundations provide the proper temperature and humidity, allowing bats to hibernate all winter, where insulated foundations were used occasionally. Bats were tracked leaving the hibernacula occasionally in late winter in Martha’s Vineyard where water was available year-round, but the bats returned to continue hibernation and survived to spring.

Unlike WSN-affected bats wintering in cave hibernacula, bats also affected by WSN and utilizing man-made hibernacula maintained good weight and overall health throughout the winter. Some bats were tracked for up to three years without suffering severe complications from WNS. Another behavioral distinction between cave-dwelling bats and those selecting human homes is that the bats wintering in crawl spaces were tracked foraging much later in the fall, meaning these bats may have entered hibernation with better fat stores for a shorter hibernation period.

Additionally, Auteri and Knowles (2020)[3] found genetic evidence of little brown bats evolving with WNS. Allelic frequencies showed significant shifts in survivors for regulating arousal from hibernation, fat breakdown, and vocalizations.  Studies by Biodiversity Works and their partners suggest that bats hibernating in homes are less likely to succumb to WNS, allowing more time for bats to evolve to survive the disease. Therefore, Biodiversity Works is working with homeowners tolerant of bats to potentially treat the WNS fungus on their property and construct new hibernacula onsite if homeowners want the bats out of their basement. Also, they are working with contractors and homeowners to heighten awareness of bats hibernating in homes to minimize potential harm from construction or remodels.

[1] White-Nose Syndrome (usgs.gov)

[2] White-Nose Syndrome (whitenosesyndrome.org)

[3] First genetic evidence of resistance in some bats to white-nose syndrome, a devastating fungal disease — ScienceDaily