Do offshore wind turbines kill birds?

All forms of energy generation have an impact on the environment. As the UK moves towards an aggressive electricity decarbonisation programme, it is encouraging therefore to see Friends of the Earth taking the lead in carrying out an open-minded science-based assessment of the potential biodiversity impacts of marine renewables – principally meaning offshore wind turbines, tidal stream generators and floating wave devices.

The impacts of land based wind turbines on birds and bats are well-known, and often mentioned by those who oppose wind power – though I suspect wildlife concerns are almost never the principal reason for such opposition. Nevertheless, bird collisions do happen, and poorly-sited onshore wind farms in the US, Norway and Tasmania have been shown to hit populations of raptors such as eagles, vultures and hawks.

It is less clear whether any significant harm is done to birds by onshore wind in the UK – but even so, with the wind industry moving increasingly offshore because of the swelling tide of nimby opposition in the shires, it is crucial to get a handle at an early stage on whether there might be serious harm to marine biodiversity as we embark on building multi-gigawatt offshore wind farms and other energy infrastructure in the sea. Friends of the Earth commissioned Martin Attrill, a marine ecologist who is director of the Plymouth University Marine Institute, to do an expert literature review with this end in mind.

offshore wind

As the report begins by pointing out, achieving the 2030 electricity decarbonisation target recommended by the Committee on Climate Change – of 50g/KWh – will require at least a tenfold expansion of marine renewables, even if accompanied by a simultaneous new-build programme for nuclear or carbon capture and storage. Personally I would support a target of the UK securing at least 40% of its electricity from offshore wind, and substantial additional contributions from other marine renewables as rapidly as they can be scaled up.

What is most striking in the report is just how benign offshore wind and other renewables currently appear to be to marine biodiversity. There is very little evidence of any harmful impact on birds: some species of duck have been shown to take minor migratory detours to avoid wind farms, but many other seabirds tend to skim along the water surface well below the spinning turbine blades. Underwater the impact may even be positive, as the subsea concrete structures provide new reef-style habitat for shellfish and seaweed. Scientists studying wind farms in the sea off Belgium discovered “large aggregations” of pouting and cod, while the additional fish numbers seemed to attract porpoise and birds elsewhere.

Part of this benefit may lie in reducing fishing activity – the seabed of the North Sea in particular has been utterly devastated by decades of trawling: as late as the early twentieth century large areas were covered by oyster beds, these filter feeders making the waters crystal clear. Today’s muddy, turgid North Sea and soft, largely lifeless sea bed is an unnatural phenomenon, a product of the fact that by the 1970s the oyster beds and various rocky reefs had been completely destroyed by trawlers ploughing up the bottom. As Martin Attrill suggests, if offshore developments can be accompanied by no-fishing marine protected areas, these can help preserve fish stocks and provide a refuge for species which have been driven to the brink of extinction elsewhere.

Marine mammals are an additional concern – but here too the news seems to be cautiously  good. Although the driving of piles into the seabed during construction can drive away cetaceans, this is a temporary phenomenon. Badly-placed underwater tidal turbines might be expected to injure dolphins, migrating fish or diving birds, but there is so far no evidence of this. Indeed, the 1-MW tidal turbine in Northern Ireland’s Strangford Lough is near a grey seal colony and has been carefully monitored for several years – so far it seems that the seals simply avoid the underwater blades without a problem.

None of this means that development should simply go ahead without any concern. As Attrill writes in his conclusion:

However, although rapid deployment of MRE [marine renewable energy] at scale is necessary, this is not a reason to avoid deploying MRE sensitively and with care. Developers and regulators should work closely with marine ecologists and conservation groups at an early stage to identify suitable locations for the MRE and associated cabling. The Habitats Directive should be clearly complied with, in both spirit and letter. Developers should strive to enhance marine biodiversity and productivity.

I agree wholeheartedly with this. As deployment scales up in a big way, we need to keep gathering evidence of environmental impact. But there is nothing to suggest currently that biodiversity is a reason to hold up deployment – as Friends of the Earth’s Mike Childs told me on the phone yesterday: “We need to get building!”

I would also encourage marine conservation groups like wildlife trusts and dolphin conservation charities, as well as the RSPB, to be closely involved with this effort. They have many decades-worth of experience in this area, and positive engagement will be crucial. Although I haven’t studied their energy policies in detail, I don’t doubt that all of them will appreciate the urgent challenge posed by climate change – not least to the marine environment, along with ocean acidification – and would agree that we should deploy the maximum amount of clean energy with the utmost speed. Their experience can help us choose what goes where, and help guide how to minimise negative impacts and maximise positive benefits on the marine wildlife which we all value so highly.

© Mark Lynas
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