David Ross
Highland Correspondent

Laying foundations in the seabed for offshore wind farms is feared to be
damaging the hearing of harbour seals around the UK’s coast, according to
scientists.

The noise from pile driving during turbine construction could have serious
health implications for the marine mammals, ecologists from St Andrews
University are warning

They say more research is needed on how noise affects seals’ hearing and
into engineering solutions to reduce noise levels. The study is published
today in the British Ecological Society’s Journal of Applied Ecology.

There are currently 1,184 offshore wind turbines around the coast of the
UK, between them generating around 4GW of power. The next round of
construction, which began in 2014, will see hundreds more turbines
installed to generate a further 31GW, little is known about the impact of
construction noise on sea mammals’ hearing.

The St Andrews researchers attached GPS data loggers to 24 harbour seals
while offshore wind turbines were being installed in the Wash in 2012. The
data loggers collected information on the seals’ locations and their diving
behaviour.

They then combined this data with information from the wind farm developers
on when pile driving was taking place to produce models which predicted the
noise each seal was exposed to. They compared this with noise levels that
other studies show caused auditory damage.

The model revealed that half of the tagged seals were exposed to noise
levels that exceeded hearing damage thresholds.

Offshore wind turbines are installed using pile drivers – essentially large
hammers that drive the foundation posts into the sea bed – which produce
short pulsed sounds every few seconds.

The lead author, Dr Gordon Hastie of the university’s Sea Mammal Research
Unit said, “These are some of the most powerful man-made sounds produced
underwater, noise capable of travelling large distances underwater.”

He said very little was known about the impact of the pulsed sounds on
seals. However, a wealth of data existed on the effect on humans and other
terrestrial species, data which showed that powerful pulsed sounds could
damage mammals’ hearing.

“Like most marine mammals, harbour seals have very sensitive underwater
hearing at a much broader range of frequencies than humans,” said Dr
Hastie. “Seals probably use underwater hearing during the mating season and
to detect and avoid predators. They may also rely on their hearing for
navigation and finding prey.”

Seals are protected under European law and any impacts that might affect
their conservation status need to be assessed prior to the construction of
wind farms.

But Lindsay Leask, Senior Policy Manager, Offshore Renewables at industry
body Scottish Renewables, said: “The Scottish offshore wind industry is
really only just beginning to deploy technology into the marine
environment, but years of environmental surveys, required as part of a
rigorous planning process overseen by Marine Scotland, have already been
carried out.

“Developers are required to submit incredibly detailed and thorough
environmental impact assessments to Marine Scotland, which cover a wide
range of subjects, including marine mammals.”


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