Updated fall 2020
This FAQ will be updated regularly as we learn more
Electricity from wind energy is a major contributor to reducing greenhouse gas emissions from fossil fuel use and thus to reducing the impacts of climate change. Wind energy also has other environmental benefits like little or no air pollution, water, or land use. Wind power in the U.S. also supports job creation and has other economic, energy security, and sustainability benefits nationally and for local communities. However, like all power sources, wind energy can have adverse impacts on some species of wildlife, including direct impacts to birds and bats from turbine collisions, and the loss and fragmentation of species’ habitat.
Since the early 1990s, in a partnership unique among energy industries, the wind energy industry, state and federal agencies, conservation groups, and scientific organizations have collaborated to promote and conduct research to understand and address the concerns about wildlife impacts. This collaboration has been motivated by the desire to understand risks from wind energy to wildlife and develop sustainable, science-based solutions accepted by the wind industry, science and conservation, and regulatory community.
Read below for short answers to some of the frequently asked questions about interactions between wind energy and wildlife in the U.S., and check out the following resources to learn more:
How does wind energy benefit communities, wildlife, and the environment?
According to a 2019 National Audubon Society report, climate change is one of the biggest threats to wildlife. Without rapid reductions in carbon emissions from renewable energy sources like wind energy, which produces zero carbon emissions during power generation, the impacts of climate change are likely to be catastrophic to countless species. Wind energy has expanded rapidly in the past 10 years, but will need to more than quadruple by 2050 to make a significant impact on reducing the risk of a rapidly changing climate.
Wind energy has many other environmental benefits compared with energy generated from fossil fuels, including:
- Reduced air pollution including nitrogen oxides, sulfur oxides, and mercury that harm humans and wildlife.
- No water withdrawals, water consumption, or impacts to water quality during operation.
- Reduced potential for catastrophic events associated with other sources of electricity, such as nuclear accidents, which can have enormous ecological impacts.
- No habitat destruction or other impacts associated with fuel extraction and transportation.
- Limited land use, as most of the land surrounding wind projects remains available for other uses such as farming, ranching, wildlife habitat, and recreation.
- Is a sustainable source of energy.
Wind energy, which is now cost-competitive with other energy sources, also has other benefits such as job creation, and contributes to national security by providing a sustainable source of domestic energy. Learn more about wind energy and its benefits.
How much wind energy is there in the U.S.?
Wind power is already an important contributor to our nation’s energy portfolio. As of 2019, approximately 98 gigawatts of onshore wind energy production capacity are currently installed in the U.S., contributing around 6.5% of our electricity. Onshore and offshore together have the potential to contribute as much as 20% of our electricity needs by 2030, and along with solar energy, wind represents the fastest-growing source of electricity in the U.S.
As the nation’s wind energy development has expanded over the last 25 years, the wind energy industry, state and federal agencies, conservation groups, academia, and scientific organizations have collaborated to conduct the research needed to improve our understanding of risk to wildlife and to avoid and minimize that risk.
Is wind energy harmful to wildlife?
Like all forms of electricity generation, wind energy can have some negative impacts for some species. For onshore wind energy in the U.S., some bird and bat species face risk of collision fatalities, and some species of grassland and shrub land birds may be displaced due to disturbance to their breeding habitat. Read below for more information on what we know about interactions between onshore wind energy and birds and bats.
There are a few studies on possible adverse impacts of wind energy to other land-based species, such as large hoofed mammals. From the studies conducted to date, no negative effects have been found.
For offshore wind energy, most studies have been conducted at European facilities. These studies indicate some bird and marine mammal species are displaced from project areas, but substantial uncertainty exists regarding the individual or population-level impacts of this displacement. In the U.S. where there is currently only one offshore wind farm, concerns are focusing on possible risk to marine mammals and fisheries. Risk to birds and bats due to collisions is unknown, although it is assumed that these collisions are less common than at onshore facilities. However, the tools to measure fatalities at offshore wind energy facilities are not available currently.
Do onshore wind turbines pose a serious threat to birds and bats in the U.S.?
Like for wind energy, estimates of fatalities caused by other anthropogenic (human-caused) sources are not certain. However, our best estimates suggest total bird fatalities at onshore wind turbines are very low relative to other anthropogenic sources of mortality. For example, bird fatalities from wind turbines per year (estimated 234,000 – 573,000) correspond to .007% of all anthropogenic mortality, or less than 1/100th of a percent. This is orders of magnitude lower than estimates for several other sources of anthropogenic mortality, such as collisions with communication towers (6.6 million), automobiles (200 million), buildings (599 million), and from cats (2.4 billion).
Fatalities to bats from anthropogenic sources other than wind energy are not well known. Further, population sizes for many species of bats are not well known, so more information is needed to understand the significance of fatalities from wind turbines.
Additionally, there are differences in the types of birds and bats killed by different anthropogenic sources. Wind turbines likely kill raptors in greater proportions than cats do, while cats likely kill more passerines (songbirds and perching birds) than turbines. Ultimately, estimates of species-specific mortality at wind energy facilities are more useful for regulatory decisions and conservation planning related to wind energy than the cumulative national estimates that garner more attention.
There are also direct fatalities of birds and bats from the operation of fossil fuel plants, although these impacts have not been studied as rigorously as wind energy impacts have. The few studies that have been conducted suggest that birds and bats suffer both direct and indirect impacts from fossil fuel plants, including impacts from land and water use and air and water pollution.
How do we know how many birds and bats are killed by wind turbines?
Collision fatalities are estimated based on searches for wildlife carcasses at wind farms, called post-construction fatality monitoring (PCM) studies. PCM studies are usually conducted by environmental consulting firms using teams of trained field biologists and statisticians to conduct carcass searches, analyze the results, and prepare a report for the client company. Although formerly not always the case, all PCM studies now produce fatality estimates based on observed carcasses that are corrected for detection errors. Because of the efforts made by the industry to monitor and assess impacts, it is generally the case that we know far more about the number of birds and bats killed by wind turbines than we do about virtually any other cause of mortality.
Additionally, the American Wind Wildlife Institute (AWWI) has developed the AWWIC (American Wind Wildlife Information Center) database, the most comprehensive database of post-construction fatality monitoring data from onshore U.S. wind projects, incorporating both publicly available and confidentially contributed data. Technical reports published by AWWI in 2018 and 2019 describe and summarize fatality data contained in AWWIC for birds and bats to evaluate the patterns of fatalities across regions, seasons, and species. These analyses set the foundation for further studies of what bird and bat species are at risk, and where and why they are at risk. Wind companies are continuing to contribute more data to AWWIC, and further analyses of these data to better understand risk are underway.
Which species of birds are affected by wind energy? Are any threatened or endangered?
300 species of birds have been reported as collision fatalities at U.S. wind facilities for which data are available. The majority (57%) are small passerines and approximately 9% are diurnal raptors. More details are available in the AWWI report “A Summary of Bird Fatality Data in a Nationwide Database.”
For most songbirds in the U.S. for which data are available, cumulative collision mortality at wind energy facilities is estimated to represent less than 0.01% of estimated population size.
Long-lived species, including most raptors, may be more susceptible than short-lived species to population-level effects from collisions with wind turbines. Raptors such as golden eagles can be affected by collisions with wind turbine blades, and possibly by disturbing their nesting.
Two endangered species of birds, the California condor and the whooping crane, are being monitored closely to determine if they are at risk from wind energy facilities. To date there have been no reports of either species colliding with wind turbines, and innovative approaches are being employed to reduce the risk to these birds.
In the case that threatened or endangered species could be affected, wind energy operators work with the U.S. Fish and Wildlife Service and state agencies to develop a conservation plan that includes minimization and mitigation measures to address impacts.
Which species of bats are affected by wind energy? Are any threatened or endangered?
While 22 of the 47 species of bats that occur in the continental U.S. have been recorded as fatalities (24 species if data from Canada are included), just 8 species accounted for almost all (96%) fatalities. Three of those 8 (all migratory tree bat species) account for 72% of all fatalities: hoary bats (32%), eastern red bats (24%), and silver-haired bats (16%). The species composition of bat fatalities varies regionally. More details are available in the AWWI report “A Summary of Bat Fatality Data in a Nationwide Database.”
Hypotheses have been proposed for why some bat species are more affected than others, including that some bats may be attracted to turbines, though research is needed to evaluate these hypotheses.
For several species of cave-hibernating bats, white-nose syndrome (a fungal disease) causes far higher numbers of fatalities in the U.S. than collisions with wind turbines. This means it is important to address all additional sources of mortality, even though wind energy-related fatalities are very low for most cave-hibernating species over most of their range.
Little is known about population size or trends in migratory tree-roosting bats, but modeling results suggest these species may be at risk of population decline due to collision fatalities with wind turbines so it is important for the industry to continue its efforts to develop methods and technologies to significantly reduce these fatalities.
Several bat species are listed under the Endangered Species Act. Of those species, only the Hawaiian hoary bat, the Indiana bat, and the northern long-eared bat have been recorded as fatalities at wind facilities, and such fatalities have been recorded infrequently.
Do wind energy facilities disturb wildlife habitat?
The possibility and magnitude of adverse impacts due to land transformation varies with each project, landscape, and species. Wind energy facilities can extend up to over thousands of acres, although the actual amount of land transformed by project-related structures, including access roads and turbine pads, constitutes only around 5%-10% of the total project area. Some of the land transformation related to construction is temporary, for example, from burying cables or building staging areas.
Land transformation associated with development of a wind energy facility has the potential to remove or fragment suitable habitat for one or more species. Detailed studies on potential effects are limited due to cost of multi-year studies, the need to replicate studies at multiple facilities, and the wide variability of project characteristics (including landscape features and species present). Many of the available studies focused on grassland and shrub land birds, whose populations already appear to be declining due to habitat loss from other development (e.g. agriculture, range management, urbanization, and other energy development). Studies at wind energy facilities have shown species-specific responses that may not be consistently observed across study sites – see examples here, here, and here. Additional and replicated studies are needed to evaluate potential effects.
There have also been few studies on the potential benefits that wind energy could have on habitat. In many cases, wind projects allow landowners to retain land instead of selling off that land to residential or commercial developments that would result in total loss of habitat. Wind farms require no fuel to generate electricity; therefore, increasing the use of wind energy reduces habitat disruption related to fuel extraction and processing for other energy sources.
What do we know about possible risk to wildlife from offshore wind farms in the U.S.?
As of 2019, there is only one offshore wind facility operating in the U.S. Therefore, there is very little information on potential wildlife impacts for U.S. offshore wind farms.
Offshore wind energy in the U.S. appears poised for major expansion as numerous leases have been issued for development in state and federal waters. Future research will increase understanding of the environmental impacts of offshore wind energy on marine wildlife.
What are the laws, regulations, and rules protecting wildlife around wind energy facilities?
Wind energy developers must comply with federal laws like the Migratory Bird Treaty Act (MBTA), the Endangered Species Act (ESA), and the Bald and Golden Eagle Protection Act (BGEPA). The ESA and BGEPA may involve applying for federal permits if covered species are present, and permits may prescribe specific conservation measures tailored to the project and species. Most developers of onshore wind farms follow the voluntary U.S. Fish and Wildlife Service Land-Based Wind Energy Guidelines, which lay out a process for determining what species are present at a site and what steps developers should take to avoid, minimize, and offset wildlife impacts if needed. Examples include relocating or removing arrays or individual turbines, restricting construction or curtailing operations during certain times of the year or under certain conditions, or restoring habitat in a different location to offset habitat that is disturbed by the wind farm. Policies around these laws and their enforcement change occasionally, and wind developers must work closely with legal experts and regulators when planning new wind projects.
For offshore wind energy development, additional federal laws may apply, including the Marine Mammal Protection Act and the Magnuson-Stevens Fishery Conservation and Management Act. Offshore wind developers may need to apply to permits under these laws as well as some of the laws discussed above depending on the species present.
State requirements and recommendations vary from state to state. These can include independent studies of wildlife populations in the area and analysis of the potential impacts of the wind farm. Some states have specific regulations related to potential wildlife impacts of wind farms and some do not, but in all cases the federal Wind Energy Guidelines lay out a process for developers to work with state agencies.
Why can’t wind companies just build wind farms where they won’t affect birds or bats?
Wind farm siting (where wind facilities and individual turbines are located) is both critical and challenging. Different areas of the country have different available wind resource, i.e., how much electricity can be produced, costs of producing and transmitting electricity, and the cost to purchase the electricity from the facility owner. Other constraints include access to transmission lines, land ownership, military or other land and airspace-use restrictions, topography and geology, as well economic viability including whether there is a purchaser for the electricity produced. All of these factors must come together to make a site viable.
Additionally, birds, bats, and other wildlife are present virtually everywhere in the U.S., so it is not possible to avoid some overlap with some species. Therefore, it is important to understand which species are most at risk from impacts of wind energy siting and operation. There are guidelines and tools to help wind developers avoid areas of greater wildlife concern to the extent practicable, but since it is not possible to avoid all potential impacts to wildlife, it is also important that wind companies have access to tools and strategies to minimize and offset impacts.
What is being done to make wind energy safer for wildlife?
Since the early 1990s, in a partnership unique among energy industries, the wind industry, state and federal agencies, conservation and scientific organizations, and academia have collaborated to promote and conduct research to address the concerns about wildlife impacts.
Several initiatives are engaged in this unique collaborative effort, including the American Wind Wildlife Institute (AWWI), the Bats and Wind Energy Cooperative, the National Wind Coordinating Collaborative, and the Wind Wildlife Research Fund. Similar efforts are beginning to emerge for offshore wind-wildlife research such as the Responsible Offshore Science Alliance, the Pacific Ocean Energy Trust, and state led initiatives such as New York State Energy Research Development Authority, California Energy Commission, and others. State and federal agencies including the U.S. Department of Energy, U.S. Fish and Wildlife Service, and U.S. Geological Survey have also been involved in this collaborative research effort, and offshore-focused agencies including the Bureau of Ocean Energy Management, and the National Marine Fisheries Services and Office of Protected Resources within the National Oceanic Atmospheric Administration are developing similar efforts for offshore wind energy.
As a result of this collaborative effort, researchers are using data collected from wind farms on bird and bat fatalities to better understand what species are at risk, where, and why. This understanding is helping to inform strategies to reduce risk.
Strategies to reduce risk include:
- Avoiding impacts through siting. Based on extensive consultation, in 2012 the U.S. Fish and Wildlife Service published voluntary guidelines for wind project siting. Some states have also published their own guidelines, which may include identifying areas with high conservation value, unique or rare natural communities, major avian migratory routes, or critical habitat for endangered species that could be avoided. Effective guidelines require a clear understanding of the species of concern and evaluation of the risk posed to these species.
- Minimizing impacts through curtailment (shutting down turbines). This approach aims to reduce bird and bat collision fatalities by slowing turbine blade rotation during periods where risk of collisions is high. Studies show reductions in bat fatalities from curtailment at low wind speeds. Researchers are exploring whether using additional variables, such as bat activity, temperature, or changes in barometric pressure, can help reduce bat fatalities while minimizing loss of energy production in what is referred to as “smart curtailment.” Another approach called “informed curtailment” involves people or technologies signaling turbine shutdown(s) when certain species are detected. Automated detection technologies include tracking California condors with GPS transmitters, camera-based systems that detect eagles, and ground-based radar that detects large raptors.
- Minimizing impacts through deterrence. Technologies are being developed and tested that aim to deter target species of birds and bats, reducing fatalities while allowing turbines to operate normally. One approach being tested is using specific types of sounds to deter birds or bats.
What are the next steps for expanding wind while protecting wildlife?
Wind energy is a key component to the move toward renewable energy sources that can play a critical role in stemming climate change. As the industry grows, it is important to continue efforts to better understand possible wildlife impacts from wind energy and improve measures to reduce those impacts. There has been extraordinary progress in the last decade, and there is more work to be done. Continued efforts are needed to improve risk assessment and expand investment, development, and evaluation of technologies and strategies to minimize collisions. In many cases, replicated studies at multiple wind farms are needed to better understand risk and effectiveness of different strategies to reduce risk. Better data on population sizes and dynamics is needed for several key species to evaluate potential population-level significance of impacts from wind energy.
Making significant progress on these research priorities will provide critical knowledge necessary for informed management practices so that wind energy can expand while conserving wildlife. Collaborative initiatives working to understand and solve wind-wildlife challenges demonstrate a commitment to finding science-based solutions to achieve the many benefits of wind energy while minimizing adverse impacts to wildlife.