Wind turbines seem a good choice as an alternative renewable energy source. According to a report by the American Wind Energy Association, the United States already has annual wind power capacity of more than 25,000 megawatts. But wind energy is not without problems. The disadvantages of wind farms include noise, vibration, appearance, and the fact that they kill birds, bats, and other flying animals.
How Do Windmills Kill Birds?
A wind turbine with rapidly whirling blades conjures an image of a bird being bludgeoned and then reduced to a cloud of drifting feathers. Many birds die when they collide with turbine blades, but this is not the only way that wind farms kill birds: birds collide with turbine towers and power lines as well, and construction of wind turbines destroys bird nesting and feeding habitat, sometimes reducing the amount of available food. Wind farms constructed in bird migration routes are particularly worrisome.
Wind farms with a higher bird death toll are those that:
- are new: studies suggest that, over time, birds adjust and learn to avoid turbines
- are built in bird migration routes
- are built on ridges and upwind slopes
- run when visibility is poor: in rain and fog, and in the dark
- include older, shorter turbine designs
- exist in established bird breeding or feeding habitat
How Many Birds Does Wind Power Kill?
No one really knows how many birds die each year as a result of the growing wind power industry. Most studies focus on only one or two wind farms and many don’t take into consideration the number of birds killed compared with the amount of energy produced. In addition, studies may overestimate the death toll (using data collected at a place or time where many birds died to predict over large areas and time spans), or underestimate it (bird carcasses are missed in rough or brushy terrain, or are removed by scavengers).
Published studies suggest that wind farms vary considerably in the risk they pose to birds. Some wind turbines don’t appear to kill any birds, while others are believed to kill as many as forty birds per turbine per year. While these reports tell us a lot about the importance of studying the probable impact on birds when planning a wind farm, and locating the turbines appropriately to minimize the risk, they tell us little about the total number of birds, and other flying animals, killed.
Bird Deaths - Comparing Wind Turbines with Other Causes
When considering the impact of wind power on bird populations, it’s important to consider it in the context of all bird deaths caused by human activities. Benjamin Sovacool, Assistant Professor at Lee Kuan Yew School of Public Policy, has attempted to put the issue in perspective (Sovacool 2009). Using the data currently available, Sovacool estimates that wind farms in the United States cause 0.3 – 0.4 bird fatalities per gigawatt-hour (GWh) of electricity produced. If these figures are correct, then US wind power generation killed about 7000 birds in 2006.
Using the same methods, Sovacool estimates that nuclear power generation kills about the same number of birds per GWh as wind power, and that producing power with fossil fuels kills nearly fifteen times as many birds per GWh. If Sovacool is right, power generated from fossil fuels killed more than 14 million birds in 2006, and a move from fossil fuel power generation to wind farms would actually save many birds.
For further comparison, the National Wind Coordinating Committee estimates the following annual bird deaths from various causes in the United States:
- 98 million to 980 million fatal collisions with buildings and windows
- 60 million to 80 million deaths caused by automobiles
- 4 million to 50 million fatal encounters with communications towers
National Audubon estimates that roaming cats kill millions of birds each year in North America.
All estimates of bird deaths due to human activities are likely to be high because of the tendency to gather data in problem areas.
Making Wind Farms Safer for Birds
Future wind power development can kill even fewer birds if the right precautions are taken:
- More study is needed to get better data on the actual bird death toll due to wind power.
- Wind farms should not be built on bird migration routes, or in areas where large numbers of birds gather for any reason.
- Wind turbines should be tall (200 to 260 ft.) to avoid locating blades at a height where birds tend to fly.
- Turbines should not provide potential perches for birds.
- Where bird collisions are likely, turbines should be shut down when visibility is poor.
While the data we currently have is certain to be inaccurate, it appears wind power can actually save many birds if an increase in this renewable energy replaces power generation from fossil fuels.
Sources
"Avian Collisions With Wind Turbines." Erickson, Wallace P., Gregory D. Johnson, M. Dale Strickland et al. National Wind Coordinating Committee. 2001
"Avian Mortality From Wind Power, Fossil-fuel, and Nuclear Electricity." Sovacool, Benjamin K. Energy Governance Program, Centre on Asia and Globalisation, Lee Kuan Yew School of Public Policy, National University of Singapore. 2009.
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