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Wind Energy Threat to Bats Growing

Updated 09/04/2020

The cumulative impact of wind power facilities in killing migratory bats threatens to become an environmental crisis that cannot be ignored (O’Shea et al. 2016). By 2012, more than 600,000 bats were being killed annually (Hayes 2013). By 2014, this number had risen to 2.22 million annually,  and the number is likely substantially higher today (Smallwood 2020). The Bats and Wind Energy Cooperative ( has made outstanding progress in developing credible assessment methodology and potential mitigation techniques. However, there still is no consistent implementation or sufficient guidance on mortality thresholds that should trigger mitigation (Arnett 2012). In most cases, the only mitigation is on behalf of already listed endangered species (negotiated through Incidental Take Permits under Section 10 of the Endangered Species Act).

Management and permitting agreements are often left to the discretion of local entities who have little or no experience in wildlife or other environmental issues, though their decisions can have far reaching national and international consequences. Further complicating matters, there remains a paucity of credible science to document population sizes or forecast long-term mortality impacts, too often leaving costly litigation as the only option for resolving controversy.

Proactive companies who have provided funds and taken risks to help scientists conduct the research required to solve problems are inadequately rewarded, and an unfortunately large number of others have gained an economic advantage by failing to implement even the simplest, most cost-effective mitigation recommendations, for example feathering blades at low wind speeds. This approach can reduce bat mortality by 77 percent over a fall season of 75 nights at a cost of only 1 percent of total annual output (Arnett et al. 2010).

Education at many levels is urgently needed in order for both bats and proactive companies to benefit in time to avoid a costly environmental confrontation. At current rates of wind industry expansion and resulting bat mortality, additional species almost certainly will be driven into endangered status, risking a backlash from traditional environmentalist supporters, not to mention the cost of increased endangered species mitigation and litigation. Though communication with landowners and decision makers can be extremely important, nothing is likely to prove more immediately effective than simple provision of clear industry incentives.

One possible approach to avoiding public demands for heavy-handed government regulation is for conservation and industry leaders to cooperate in developing criteria by which companies can be objectively ranked relative to their collaboration in preventing or mitigating harm to bats, birds and other wildlife. These rankings could be used to help green energy investment advisors guide their clients, many of whom seriously care about the environment. Even investors whose only concern is avoidance of costly delays and litigation likely could be influenced. Such an approach need not require perfection to serve as an important guide in the right direction.

Criteria could include the extent to which a company avoids high-risk locations, incorporates approved mitigation techniques and collaborates with scientists to monitor mortality and improve problem solving techniques.

Finally, in discussing how to meet energy needs, we must keep in mind that energy conservation is the single most important step we can take toward independence. According to the U.S. Department of Energy (2011), by using simple in-home procedures, Americans could cut their annual energy bills by 25 percent without reducing their standard of living.

Key Issues of Concern

Approval Process for New Facilities

Pre-siting Environmental Impact Studies: These are typically under-funded, inadequate to evaluate true wildlife risks, and often do not include objective, scientific peer review, either of methodology or results. Most are too short in duration and fail to consider the potential for turbines to attract bats in numbers not present during pre-siting monitoring. They also lack standardized procedures, rendering them virtually useless in making broad comparisons that could facilitate an understanding of potentially cumulative impacts or of the relative risks associated with varied habitat and topography. Furthermore, findings are typically considered proprietary and seldom are disclosed to public decision makers until after decisions are made. This renders them meaningless to the permitting process.

Jurisdiction in Decision Making: Although many permitting decisions involve migratory or endangered species for which local decisions may have state, regional or even international impact, these broader, potentially cumulative impacts, are seldom understood or considered in local approval processes. The potentially serious consequences of such decisions are especially clear when building along major migratory flyways. In addition, threats to already declining species, for which cumulative impacts could needlessly push them into endangered status, are often ignored.

Project lobbying with local communities: In their rush to gain rapid approval of projects, proponents too frequently gloss over critical wildlife issues, claiming wildlife agency and organizational approvals that are reported in a highly misleading manner. Balanced, objective viewpoints are not always portrayed when biological issues and data are disseminated. Furthermore, statements that no endangered species will be threatened ignore the fact that already declining species could be forced into endangered status.

Monitoring and Reporting Mortality Impacts for Operational Facilities

Post-construction Impact Studies: Most post-construction studies are too poorly funded to obtain credible results and are biased against detection of small birds and bats. Mortality searches often have been conducted without objective peer review from the scientific community on methodology, results, or interpretations of findings. Field sampling biases, most notably scavenger removal rates (documented as high as 70% in 24 hours), and searcher efficiency (often less than 25% in vegetated terrain) are often not accounted for. Mortality searches are often conducted at seven, 14 or 28-day intervals, leading to significant underestimation of fatalities, especially for small birds and bats.

Failure to Measure Population Impacts: Proponents of wind energy development often state that reported mortality is inconsequential to overall populations. However, there are no adequate efforts to document long-term fatality rates relative to local or migratory population sizes, and regional comparisons are often inappropriate. The two facilities at Meyersdale, Pennsylvania and Mountaineer, West Virginia, where more than 2,000 bats were killed in just six weeks in 2004, are no longer even being monitored. Without ongoing monitoring, it is impossible to say that cumulative impacts will not affect species populations, especially those that must migrate long distances where multiple wind power facilities will be encountered. Claims that wind power facilities contribute only a small part of overall mortality are not substantiated with empirical data. They also do not consider the numbers of turbines planned for the future, the fact that current fatality is underestimated, or that at least some impacted species are already in decline.

Industry Accountability

Avoiding High Risk Locations or Finding Solutions to Avoid or Minimize Risks: Although the need for renewable energy sources is substantial, this should not exempt associated industries from the accountability and monitoring required to understand and solve problems. The wind industry has not been held adequately accountable for wildlife kills, and is devoting inadequate resources to finding preventative solutions.

Building permits should require standardized assessment of all turbine-caused wildlife mortality, subject to prompt public disclosure and peer review, including a requirement to address any mortality findings deemed by objective outside review from the scientific community to be potentially unsustainable (either locally or cumulatively over broad areas of a species’ distribution). Processes are also needed to ensure standardized compliance with all permitting requirements for monitoring at each location through the life of projects (to be passed on with each transfer of ownership).

Areas already known to be exceptionally high risk, such as those near extra large aggregations of birds or bats should be avoided until solutions to prevent or minimize mortality are tested and their efficacy confirmed. Such sites include major migratory flyways, key foraging, nesting, and roosting habitats, and large bat caves. There is little evidence that such areas are being avoided by industry. In Texas, companies have repeatedly sought support to build facilities in one of our continent’s most important migratory bird flyways as well as dangerously near the most important bat caves of the New World, caves supporting many millions of bats.

Safer Wind Turbines and Energy Conservation

Wildlife Safe Turbines: Wind turbines have been developed that report no wildlife mortality, and some of their unique designs appear unlikely to pose threats to either birds or bats. This is promising and needs further testing. Such turbines are anticipated in varied sizes, useful from rooftops to full industrial, and some are reported to be equally or more efficient in power production than currently built turbine designs. Such alternatives should be seriously considered, especially in wildlife sensitive areas.

Energy Conservation: Too little attention is being paid to energy conservation. Even at currently planned expansion rates, wind turbines are anticipated to meet only a small proportion of U.S. energy needs over the next 20 years. Without suggesting that this is unimportant, it also should be noted that simple energy conservation could significantly reduce consumption and demand without reducing human life styles or harming the environment (see, for examples).


Anonymous. 2011. Energy efficiency and Renewable Energy. U.S. Department of Energy.

Arnett, E.B., M.M.P. Huso, M.R. Shirmacher, and J.P. Hayes. 2010. Altering turbine speed reduces bat mortality at wind energy facilities. J. Wildlife Manag. 73:1077-1081.

Arnett, E.B. 2012. Impacts of energy development on wildlife: Challenges and opportunities for integrating science, management, and policy. Pp. 213-237 in Wildlife Science: connecting research with management (J.P. Sands, S.J. DeMaso, L.A. Brennan and M.J. Schnupp, eds.). Taylor and Francis, New York.

Hayes, M.A. 2013. Bats killed in large numbers at United States wind energy facilities. BioScience 63(12):975-979.

O’Shea, T.J., P.M. Cryan, D.T.S. Hayman, R.K. Plowright and D.G. Streicker. 2016. Multiple mortality events in bats: a global review. Mammal Review 46(3):175-190.

Smallwood, K.S. 2020. USA wind energy-caused bat fatalities increase with shorter fatality search intervals. Diversity 12(98), 19 pp.

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Michael Lazari Karapetian

Michael Lazari Karapetian has over twenty years of investment management experience. He has a degree in business management, is a certified NBA agent, and gained early experience as a money manager for the Bank of America where he established model portfolios for high-net-worth clients. In 2003 he founded Lazari Capital Management, Inc. and Lazari Asset Management, Inc.  He is President and CIO of both and manages over a half a billion in assets. In his personal time he champions philanthropic causes. He serves on the board of Moravian College and has a strong affinity for wildlife, both funding and volunteering on behalf of endangered species.