Are offshore windfarms a problem for whales?

Australia’s coasts could soon be home to a lot more offshore wind farms. Currently, more than 50 offshore windfarms are being proposed around Australia, with Victoria, New South Wales and South Australia all being declared or proposed areas for development.

While this could be an important part of lowering our reliance on fossil fuels, there’s debate over whether marine mammals such as whales could be affected by the construction and the ongoing operation of the wind turbines.

“It’s really hard because of course you want to try and find that balance between nature and better energies,” says Gabrielle Genty an evolutionary biologist working with marine mammals.

“But I feel like the people that are in charge of creating the wind farms need to be more aware of the situation and what they’re doing and how they’re doing it.

“They’re still thinking about how to make more money.”

Australia is ringed by whale breeding grounds for humpback and southern right whales, from Cairns in Queensland to Broome in WA, and around Tasmania and through Bass Strait and even north of Investigator Strait between Kangaroo Island mainland SA.

They are the backbone of a massive whale watching tourist industry, which includes onshore whale watching and offshore boat charters. If the animals were driven offshore, the tourist industry would be deeply affected.

Whale feeding grounds are usually in the Southern Ocean.

Whales and many other marine mammals need hearing for a variety of reasons. Some whales communicate to each other through song, while others use echolocation to guide themselves with sound. In both situations, having a relatively quiet ocean is vital, says Genty.

But wind turbines are not quiet. To create a fixed foundation for the wind turbine usually hydraulic hammers are used – these sound like gunfire and can be heard kilometres away.

“Those construction noises are very loud and very low frequency, which tend to affect baleen whales because they communicate through low frequencies,” says Genty.

“That kind of noise can also impact their hearing if they’re very close to them. So it can create hearing damage and disorientation.”

There are ways of mitigating this. Although Australia is yet to install any offshore wind farms, Europe and America have been doing this for years at this point, and they have more information about the risks.

A study earlier this year found that acoustic deterrents used to protect marine mammals were working in Europe. A team of researchers used a portable acoustic recorder and found that porpoises swam away from acoustic deterrents used at the sites, maybe as far as 7km away, while ‘bubble curtains’ can dampen the sound from the installation itself.

But once this is over and the turbines are in, there’s another (although smaller) problem  – the noise of the turbines themselves.

A paper published earlier this year suggests that as long as the turbines are under 20 MW there’s likely ‘negligible impact’ on the marine population. But for bigger turbines, the sound can spread through the water up to 700 metres. If the turbines are placed less than 1400 metres apart, the whole windfarm might end up being an ‘impact area’.

Overseas, wind turbines and whales have become a political issue. In the US an unlikely alliance — those wanting to protect whales, and Republicans against Wind Power, are coming together on whale deaths.  NOAA and other US government bodies have found no scientific evidence for offshore wind farms and whale mortality.

Most scientists only advocate for moving offshore wind farms away from areas that could be close to important areas for marine mammals, instead of not doing it all together.

“There’s a lot of whales that have certain bays that they use to avoid predators when they’re with the calf, or feeding, or resting,” says Genty.

“So, avoiding those areas is crucial, so that we avoid disturbing them.”

The biggest offshore wind farm proposed to date, Star of the South in Victoria’s Gippsland region, has been monitoring whale habitats for two years. The study, led by RPS and Blue Whale Study, will add to two years of data already collected on whale movements in the licence area in east Bass Strait.

It says that ‘an experience marine mammal observer’ is identifying the animals from a plane flying as low as 300 metres.

The company has said that the findings will be shared in early 2024.