Forecasting No Breeze
Studies do poor job of predicting bird fatalities at wind farms
Wind farmers take note: You can’t count on common forecasting methods to figure out whether the turbines will kill birds. A new study from Spain concludes that pre-construction studies are pretty bad at predicting which turbines will lead to deadly bird collisions.
“The prevention of bird collisions in newly built wind farms is a critical issue,” a team led by Miguel Ferrer of the Donana Biological Station in Seville, Spain, notes in the Journal of Applied Ecology. In a bid to ensure that turbines are built in the avian-safest places, Europe and many other nations require environmental impact assessments (EIAs) as part of the approval process. But few – if any – studies have examined just how well those EIAs predict bird fatalities once a wind farm is up and operating, the authors note. “This lack of pre- and post-construction mortality comparisons is alarming,” the authors conclude.
To fill the gap, the researchers compared EIAs done for 53 proposed windfarms near the Strait of Gibraltar in southern Spain to observed bird deaths. The Strait is a key bird migration route, and many threatened species use the area. The studies, carried out in 1999 and 2000, ultimately led to the approval of 20 of the farms, holding a total of 252 turbines. All “were built at locations where the least risk was expected based on several criteria,” the authors note, “including bird use, proximity to breeding and roosting sites, and the presence of endangered species” such as several birds of prey. Once the turbines started turning, in 2005 to 2008, the operators were required to conduct daily surveys looking for dead birds. The researchers drew on these surveys to see just how well the EIAs predicted collisions.
Overall, the surveys revealed 596 dead birds at all of the wind farms. The griffon vulture was the most frequently killed species (with 138 individuals), and songbirds and raptors (including vultures, hawks and eagles) each accounted for 36% of the corpses. On average, each turbine killed 1.33 birds per year of operation – “one of the highest mean collision rates ever reported for all bird species” at a windpower site, the authors note.
The toll was much higher than the EIAs suggested, the researchers note. And the numbers “suggest that there is no clear relationship between predicted risk identified during EIAs and actual mortality of birds (particularly raptors) after wind farms have been constructed,” the researchers concluded. Ironically, some of sites believed to be safest for birds “showed some of the higher collision rates when operating and vice versa.”
That sobering conclusion has two implications, they note: “First, during at least the last decade, environmental administrations might have been giving licenses to construct wind farms based on the wrong criteria, enabling them to be constructed in unsuitable places, as well as in safe ones.” Second, it highlights the need for “new or modified” methods to accurately assess wind turbine risks to birds. The authors highlight a number of potential problems with current methods – such as assessing the risk of whole wind farms instead of specific turbine sites – and suggest some alternatives.
It’s likely, they conclude, that future EIAs “will probably need a higher intensity of pre-construction fieldwork than is usually conducted, in order to be accurate.” – David Malakoff | September 6, 2011
Source: Ferrer, M., de Lucas, M., Janss, G., Casado, E., Muñoz, A., Bechard, M., & Calabuig, C. (2011). Weak relationship between risk assessment studies and recorded mortality in wind farms. Journal of Applied Ecology DOI: 10.1111/j.1365-2664.2011.02054.x
Image © Lasse Kristensen | Dreamstime.com
