Offshore wind turbine construction may be too loud for seals to handle, according to new research.
Researchers attached GPS devices to 24 harbor seals (Phoca vitulina) in 2012 while offshore turbines were being built around the coast of the United Kingdom, as part of a study recently published in the Journal of Applied Ecology.
”These are some of the most powerful man-made sounds produced underwater, noise capable of travelling large distances underwater,” said Gordon Hastie in a release about the pile-driving methods often used during offshore turbine construction. Hastie is the lead author of the study and a part of the Sea Mammal Research Unit of the Scottish Oceans Institute at the University of St. Andrews.
In an email, Hastie added that while researchers know very little about how seals use their excellent hearing in the wild, there’s evidence that the marine mammals can detect the underwater calls of predators such as killer whales. “Any damage to their hearing may therefore have implications for breeding success and predator avoidance in some areas.” Seals could also use hearing to navigate and find prey.
Hastie and the other researchers took data from previous studies on seals and other species that predicted what levels of noise would cause reductions in the sensitivity of the seals’ hearing. “It is important to highlight that there is a cumulative effect of sound,” he said, adding that the longer animals are exposed to loud sounds, the higher the risk of hearing damage.
There could be ways to mitigate these potentially negative effects including reducing the noise produced by pile-driving.
“The industry and regulators in Europe are currently working hard to develop strategies to limit the sound output during pile driving,” Hastie said. “Engineering solutions such as underwater bubble curtains or barriers around the piles have had some success at this.”
Using acoustic methods to deter seals could also work around construction areas if they are applied right before pile-driving. “However, it is important to highlight that there is still a lot of uncertainty surrounding the effects of underwater sound on seal hearing,” Hastie said. “Further studies to measure potential hearing damage as a result of exposure to pile-driving is sorely needed to help the industry develop in an environmentally sustainable manner.”
Still, wind farms may not be all bad for seals. Debbie Russell, a marine ecologist at the same research unit at St. Andrews and one of the coauthors of this recent study was also involved in an earlier paper in Current Biology that found some individual seals were using wind farms in European waters for foraging.
“For the seals that show this behavior, [the turbines] could provide fruitful foraging opportunities depending on the amount of other prey available in the surrounding area,” Russell told The Wildlife Society in an interview for a feature story on the impact on renewable energy on wildlife that ran in the Spring 2015 issue of The Wildlife Professional.
|Joshua Rapp Learn is a science writer at The Wildlife Society.