Offshore wind farm noise a threat to marine mammals

BUILDING offshore wind farms may be damaging the hearing of porpoises and seals, a study has suggested.

Pile driving into the seabed to create the vast foundations for the turbines generates an enormous amount of noise and vibrations.

Legislation is in place to limit the noise that marine animals are exposed to, but experts warn this may now be out of date and due for an upgrade.

Researchers from Aarhus University in Denmark reviewed data and found there was “strong support” for the theory that impulsive sounds from pile driving and air guns, for example, exceed the safe limit for some animals.

“Harbour porpoises and harbour seals are of particular interest with respect to pile driving because they are acoustically sensitive and among the most common marine mammals in shallow western European waters, a centre of the rapidly expanding offshore wind farm industry,” said study author Prof Jakob Tougaard.

Writing in the The Journal of the Acoustical Society of America, the researchers said noise regulations need to be updated to protect sea creatures against a rising din in the oceans.

The Danish team reviewed experiments from 2015 in which hearing sensitivity was measured by electrodes attached to the skin of marine animals with suction cups.

Current guidance for marine life is based on very few measurements in a limited frequency range, the experts say, and they found substantial deviations in recent studies of the impact of low frequency noise on seals and high frequency noise on porpoises.

Prof Tougaard said the observed discrepancies “can only be resolved through new and dedicated experiments”.