New High-Capacity Wind Turbines Significantly Reduce Collision-Related Avian Mortality

While wind power has received great support as a carbon-neutral, renewable energy source, it is not without ecological problems. Smallwood and Karas (2009) found that wind turbines in the Altamont Pass Wind Resource Area in Central California were responsible for the deaths of thousands of birds from 1998 to 2003. Many of the birds that were killed were endangered or otherwise protected species.
Fortunately, as outdated wind turbines are replaced with newer, more efficient ones avian mortality decreases by 66%. Nonetheless, it is important to consider migratory pathways and avian habitats when constructing new wind farms in order to best mitigate the environmental impacts of such projects. Noah Proser

Drewitt, A.L., Langston, R.H.W., 2008. Collision effects of wind-power generators and other obstacles on birds. N.Y. Acad. Sci. 1134, 233–266.
Smallwood, K.S., Karas, B., 2009. Avian and bat fatality rates at old-generation and repowered wind turbines in California. Journal of Wildlife Management 73, 1062—1071.

Smallwood and Karas counted the number of birds killed by wind turbines in the Altamont Pass from 1998 to 2003. In 2005, the Diablo Winds Energy Project replaced 126 inefficient turbines with 31 higher capacity turbines. With a higher surface area and lower rotor speed these turbines were expected to be less dangerous for birds flying through the pass. Subsequently, the researchers conducted another survey from 2005 to 2007 to determine whether the new turbines significantly reduced avian mortality. In order to avoid complications from differing bird populations over time, both old and new turbines were included and compared in the later survey.
The authors found that the new turbines killed 66% fewer birds than the old generation of turbines. Furthermore, since the new turbines have a much higher capacity, modern wind farms can be more sparsely populated or smaller while still producing the same amount of power. This reduction in size or density can further reduce the risk for birds. Despite the advantages of the new generation of turbines, these levels of avian mortality may still be unacceptable. For this reason, future wind power proposals should be carefully evaluated to avoid the migratory patterns of endangered birds.
Unfortunately, some level of bird kills may be inevitable when it comes to wind power regardless of the precautions taken. With that said, wind power should not be abandoned. After all, turbines are not the only anthropogenic causes of avian mortality. Untold numbers of birds are killed each year from collisions with windows, television and radio broadcasting towers, and power lines (Drewett and Langston 2008). In all likelihood, wind turbines are responsible for a minute amount of overall avian mortality. Moreover, wind farms can replace power plants, which pollute the habitats these birds depend on. We should make efforts to minimize bird kills from wind turbines; however, avian mortality is not likely to be a vital issue in the future of wind power.

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