Can Offshore Wind Farms Help Seals Rather Than Harm Them?
“Save the seals” has been a rallying cry of opponents of offshore wind turbines, who fear the massive machines will harm marine mammals such as dolphins and whales. Now scientists in the U.K. have discovered that wind farms may help seals by attracting a smorgasbord of sea life for them to eat.
The researchers followed the travels of GPS-tagged harbor and gray seals at the 88-turbine Sheringham Shoal Offshore Wind Farm in the U.K., and at the 12-turbine Alpha Ventus project, a wind farm 37 miles off the German coast in the North Sea.
They found that seven of 22 seals tagged in the U.K. visited the Sheringham Shoal wind farm. One seal made 13 trips to the project, methodically swimming from one turbine platform to the other. The North Sea seals weren’t quite as adventurous, with just four of 96 tagged animals making the journey to Alpha Ventus.
The seals also liked to follow undersea oil and gas pipelines, according to a study published Monday in the journal Cell Press.
Why do seals visit wind farms? Because that’s where the food is, apparently. The scientists speculated that the undersea part of turbine platforms serves as an artificial reef, attracting critters that the seals like to munch on.
“The data strongly suggest that these structures were used for foraging, and the directed movements show that animals could effectively navigate to and between structures,” the scientists wrote. “Furthermore, once within the wind farm area, the probability of foraging significantly increased towards individual structures for the two seals that spent the majority of their time near the turbines.”
The video below shows four of one seal’s 13 trips to the U.K. wind farm. The white dots represent turbine platforms; the red line is the seal’s movements.
Whether offshore wind farms are a good thing for the seals in the long run remains to be seen, according to Debbie Russell, the study’s lead author and a postdoctoral research fellow at the University of St. Andrews in Scotland.
“A key unanswered question is whether, for the most part, these structures increase or simply concentrate seal prey species,” she said in an email. “If such structures increase the overall abundance of prey in the environment, they may provide sustainable new foraging opportunities for predators. In this case, such structures could be designed to maximize any potential ecological benefits.”
“On the other hand, in contrast, if prey, previously sparsely distributed, simply congregate at such structures, this makes them vulnerable to be hoovered up by marine predators, such as the seals, which may have negative consequences for the populations of prey species,” she added.
Although wind farms may attract seal chow, they still can pose threats to the animals, Russell noted. That’s particularly the case during construction, when seals are at risk of injury or death from boat collisions and heavy equipment.
Even after a wind farm has begun operating, higher noise levels and occasional visits from maintenance crews can disrupt seals’ behavior.
For now, given an estimated population of 55,000 harbor seals and 65,000 gray seals in the North Sea, there are far more seals than wind farms.
That balance is changing, however.
“At present wind farms cover a small proportion of the extent of the at-sea distribution of seals,” Russell said. “As wind farms become more extensive, many more seals will likely be affected.”