Media & Education
BATS Magazine

Volume 22, Issue 2, Summer 2004

Wind Energy & the Threat to Bats

BCI, industry and government join to resolve a new danger facing America’s bats

By Merlin D. Tuttle

The big turbines, which look like high-tech windmills and turn wind into electricity, are going up on windswept sites around the United States. But as wind farms proliferate, an unforeseen problem is turning up: Migrating bats are crashing into the spinning blades of the turbines in disturbing numbers.

This recently discovered issue could get worse in a hurry. Wind power is the fastest-growing segment of the U.S. energy industry, and tax subsidies that are expected from Congress this year could trigger a construction boom that will put thousands of wind turbines on high-risk ridges and mountaintops, especially in the eastern United States.

To prevent serious threats to bats, Bat Conservation International is working with industry and federal agencies to determine exactly why bats are fatally flying into the turbines and how that can be prevented. The Bats and Wind Energy Cooperative includes BCI, the American Wind Energy Association (AWEA), the U.S. Fish and Wildlife Service and the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL).

The issue of bat kills at wind farms was widely neglected in early wind-power assessments simply because bats, unlike birds, have no broad-based legal protection. Reports of two or three bats per turbine being killed each year at some facilities seemed a relatively small price to pay for clean energy. Such figures, however, can be misleading. We now realize that many more bats may have been killed but not counted. Moreover, wind farms increasingly contain hundreds, sometimes thousands, of wind turbines; if even a few bats are lost at each turbine, total losses can add up quickly. With many thousands of new turbines being planned nationally, the risk of serious, cumulative impacts cannot be ignored.

The reality was driven home late last summer when weekly surveys beneath 44 giant turbines at West Virginia’s Mountaineer Project discovered that an estimated 2,092 bats of seven species had been killed. However, since no surveys were conducted during the first half of the peak mortality period in August and since unknown numbers of bats were removed by scavengers between the seven-day search intervals, the total number of bat fatalities could easily approach 4,000.

The Mountaineer Project is the first large wind-energy site in eastern North America to be built on a high ridgeline. Exceptional bat kills are also being reported at a Tennessee wind farm on a mountaintop; 85 bats are being killed there each year at just three turbines. These are the only two wind farms built so far on ridges and mountaintops in the Eastern states.

For more than a decade, biologists have been raising concerns about ridge-top wind sites as potential threats to migrating birds, but bat migration was rarely considered. With major bat mortality confirmed at the only two Eastern wind-turbine projects located on ridge- and mountaintops, the potential for devastating cumulative impacts is clear, especially since wind power is expanding so rapidly.

Ninety-two additional turbines already have been approved for the same West Virginia ridge where thousands of bats were killed last year. In fact, if all ridge-top turbines already approved are built, the total within 50 miles of the site could reach 410 turbines. If local kill rates continue unabated, these turbines alone could kill more than 30,000 bats in a single season!

To address this urgent issue, BCI hosted a planning session last December that brought together leaders from the Fish and Wildlife Service, NREL and AWEA. The group agreed to sponsor a Wind Power Generation Technical Workshop to develop an expert consensus on how to prevent further bat deaths.

The meeting, funded by AWEA and NREL and hosted by FPL Energy (America’s largest wind-power producer), was held in Juno Beach, Florida, February 19-20. Top bat experts from the United States, Canada and the United Kingdom developed the research priorities they consider essential to preventing additional bat kills.

Participants agreed that consistent regulatory review and financial incentives for addressing environmental concerns are currently inadequate. They also stressed the importance of developing scientifically credible mortality estimates as soon as possible and emphasized the vital need for greater sharing of information. Most reports of bat mortality at turbines resulted from studies of the threat to birds, not bats. These mortality surveys were conducted at only one- or two-week intervals and paid inadequate attention to such complicating factors as the efficiency of the searchers in finding dead bats and the likelihood that many bats were eaten by scavengers between surveys. There is an immediate need to document real mortality rates and to observe how bats are interacting with turbines.

Bats seem to be substantially more vulnerable to wind turbines than birds, but we have no idea why. They may be attracted to turbines by either sound or visual cues or to nocturnal insects lured to or otherwise concentrated around turbines. We do not know why most bats are killed between late July and mid-September, mostly in August. They may be migrating, but the migration times typically last longer than the period of primary mortality. We also have no idea how lunar or weather patterns may affect mortality risks.

Solutions will not be found until detailed observations are made, and these will require long hours of daily and nightly monitoring at problem sites. Night-vision and thermal-imaging equipment, echolocation detectors and marine radar have all been identified as tools that may help in assessing problems. The costs for appropriate technology and sufficient human resources are high, and the time until next August is short. It is imperative that we immediately develop reliable methods for identifying and avoiding highly sensitive locations, stop attracting bats to turbines, act to reduce their vulnerability, learn to predict and respond effectively to high-risk time periods or delay further construction along sensitive ridge and mountaintop areas. Given anticipated pressures, it is urgent we get a fully equipped field team in place no later than August 1, 2004, and that is our goal.

Armed with the advice of leading experts on bats and relevant technologies, members of the Bats and Wind Energy Cooperative agreed to jointly fund a Project Coordinator at BCI. Ed Arnett, a biologist of exceptionally relevant experience, officially assumes that position June 15. His immediate goals include developing a project website for information sharing, completing guidelines for risk-assessment and mortality studies, facilitating required peer review and communication, and organizing and participating in field research.

The new Bats and Wind Energy Cooperative has been formed. Expert guidance has been obtained and priorities have been set. But nothing can be accomplished until we make essential observations and find and implement solutions. Cooperation in funding the required research will be the true test of our collaboration.


Finding Solutions
Red bats (Lasiurus borealis) were so common in the 1870s that naturalist Edgar Mearns described great migrating flocks that passed overhead for days at a time. Such sights vanished long ago. But today, this forest bat faces a major new threat: It is the species most frequently killed at wind turbines.

Without immediate action, the cumulative impact of thousands of additional wind turbines on ridges along the red bats’ migratory routes could prove disastrous – not only for them but for other species as well, including the endangered Indiana myotis (Myotis sodalis).

Bat Conservation International plans to initiate field studies by this August to examine the problem and seek solutions, and we have committed to hiring a project coordinator. This critical work, however, will require major financial investments that exceed our current resources. Your help in any amount is urgently needed.

For more information, contact

MERLIN D. TUTTLE is Founder and President of Bat Conservation International.

MERLIN D. TUTTLE is Founder and President of Bat Conservation International.

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