Estimating the extent of fatal bird collisions with wind turbines

As the US seeks to expand its wind energy sector, a new study sheds greater light on the impact of wind turbines on wildlife. 

While wind energy is usually seen as a ‘green’ alternative to fossil fuels, there are still some concerns about the large numbers of birds that apparently die in collisions with the massive turbines. Previous estimates of bird mortality in the US were not very specific, calculating collisions at anything from 20,000 to over 573,000 birds per annum. But now a study has re-examined the issue, looking at data from only monopole wind turbines which will eventually replace all the old lattice tower turbines.

The study estimated that between 140,000 and 328,000 birds were being killed in collisions with monopole turbines every year in the US. Although this is a smaller number than previous estimate, it nonetheless accounts for a considerable number of bird deaths.

In addition, it appears that there is a greater risk of fatal collisions with taller turbines. This is a real problem, as larger wind turbines may provide more efficient energy generation. Consequently, it is expected that new wind farms will contain even bigger turbines, which will result in even more bird deaths. Future developments therefore will have to give very careful consideration to potential wildlife impacts when planning the type of turbine to install.

It remains largely unknown exactly which bird species are being impacted by collisions with wind turbines. This is even more frustrating in light of the recent controversial ruling on bald and golden eagles. At the moment, if the US Department of Energy achieves its goal of generating 20% of total energy from wind power, then it is estimated that at least 1.4 million birds will be killed annually, but we have no idea which species will be affected the most.

There is still insufficient information on the effects of wind energy on wildlife. And even when there is data available, it can be incredibly difficult to access. In this study, the authors were frustrated by the lack of publically-available data on bird collisions in many regions of the US, including the entire southwest. They acknowledge that this may have skewed their mortality estimates somewhat, but the only way that such models can be improved in the future is if industry reports no longer remain confidential.

We need more information and more studies. Only this will allow the most appropriate sites for future wind turbines to be chosen, which will hopefully help to minimise the number of fatal bird collisions in the coming years.

Reference: Scott R. Loss, Tom Will, & Peter P. Mara (2013). Estimates of bird collision mortality at wind facilities in the contiguous United States Biological Conservation, 168, 201-209 DOI: 10.1016/j.biocon.2013.10.007