[LUM#19] Stolen Lives
Every year in France, tens of thousands of birds are struck in mid-flight by the blades of wind turbines. In light of this high mortality rate—and as the French government plans to double its wind farm capacity—the program MAPE program brings together private and public stakeholders to ensure that wind power does not blow these “people of the wind” away.
On the morning of January 16, a golden eagle was found dead at the base of a wind turbine at the Bernagues site in the Hérault department (France 3, January 27, 2023). Bird mortality attributable to wind turbines is a phenomenon whose true extent remains unclear. “The figure often cited is 7 deaths per year per wind turbine in France. This figure is likely lower than the actual number and, more importantly, does not distinguish between species; yet birds of prey, which rely on wind to fly, compete for space with wind turbines,” explain Olivier Duriez and Aurélien Besnard, biologists at the Center for Functional and Evolutionary Ecology in Montpellier* and the principal investigators of the MAPE project (Bird Mortality in Wind Farms).
Launched in 2019 at the initiative of the DREAL Occitanie and the League for the Protection of Birds (LPO) in collaboration with the Maison des sciences de l’Homme, MAPE brings together a consortium of public and private stakeholders—including 25 wind farm operators—to reduce bird mortality. In response to public expectations, more and more wind farms are equipping their turbines with automatic detection systems (ADS) that stop the blades when a bird approaches. “The first step was to provide operators with a scientific protocol to evaluate the effectiveness of these systems, for which there are almost no studies, ” explains Aurélien Besnard. This is because collisions continue to occur even in wind farms equipped with ADS.
Theft Detector
To better adjust these SDA settings, researchers have also developed EolDist. This free online application calculates the minimum distances required to detect a bird by cross-referencing—using a built-in database—the speed and flight pattern specific to each species with meteorological data and the turbine’s deceleration time. “Take the golden eagle, for example, which flies at an average speed of 15 meters per second. If the wind turbine takes 41 seconds to stop, we’ll need to detect the eagle at 875 meters to avoid a collision,” explains Olivier Duriez. While some tests have been conducted, more are needed to improve the application’s reliability, but operators are reluctant to carry them out. “Eoldist’s results tend to call into question the very logic of these detection systems,” notes Aurélien Besnard. “If wind turbines stop every time a bird passes within 500 meters, they’ll be stopping all the time—which, in itself, remains the best way to prevent bird mortality, but isn’t economically viable.”
At the same time, researchers are also studying the effect of environmental conditions on collision risks: “Can fog, rain, and wind contribute to collisions? Does the terrain play a role?” asks Olivier Duriez. They are exploring these avenues by analyzing videos of collisions captured by wind turbine cameras. “Having operators in the consortium gives us access to this footage, which remains fairly sensitive data for the wind farms.” The results could help improve the selection of sites for wind farms and allow for adjustments to their operations when weather conditions are conducive to collisions.
Depleted Populations
Another goal of the MAPE program is to raise awareness of biodiversity issues by developing EolPop, a simple application for calculating the impact of mortality on a species’ population dynamics. “Losing an eagle or a chickadee does not have the same consequences for the long-term viability of the population,” warns Olivier Duriez. EolPop allows its users—whether wind farm operators or nature conservation organizations—to cross-reference survival and fertility rates for each species with data on population sizes. “The approach we’ve taken is to compare the population sizes we would have in 30 years with and without the wind farm.”
Let’s take the golden eagle as an example: with one death per year in a population of ten pairs, the population will become extinct in less than 30 years. “Fortunately, not all species are affected to this extent, but this helps put things into perspective,” the researcher continues. “Today, some consulting firms say that one eagle a year isn’t much. But not much compared to what? Here we have figures based on robust calculations,” adds Aurélien Besnard. These figures cast a rather grim light on others: France currently has 8,000 onshore wind turbines and plans to double its wind farm capacity by 2028. Wind power has a bright future; the golden eagle, not so much.
Bird's-eye views
Why do these collisions between birds and wind turbines occur? To understand this, research is being conducted as part of MAPE on bird vision and, more specifically, on their ability to perceive contrast—in other words, whether they are able to distinguish a wind turbine against a gray sky. “The doctoral student conducting this research has carried out tests on 35 bird species. The result is that their contrast sensitivity is between 7 and 30 times lower than ours,” explains Olivier Duriez. The same applies to the perception of rotational movement, which appears to be weaker in birds. “At high speeds, the buzzards and turtledoves tested detect rotation very well, but below three or five rotations per minute, perception becomes much more difficult,” the researcher continues . This information could enable wind farm operators to adjust turbine speeds to accommodate birds’ vision. In Norway, some wind farms are attempting to improve contrast by painting one blade of each turbine black (France Inter, August 29, 2020). The effectiveness of this method, however, is mixed.
*Cefe (CNRS, UM, IRD, EPHE, INRAE, Institut Agro, UPVM)
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