I’m pleased to tell you about a new WWF report released today which shows how reducing the underwater noise that offshore wind farm construction produces could help harbour porpoises thrive in the North Sea (it’ll make great reading with the weekend papers).
Securing the maximum possible deployment of renewable energy at minimal cost to biodiversity is a key priority for us. It’s essential both to meet the UK’s commitments on climate change and renewable energy generation and to avoid long-term impacts on marine ecosystems. At the same time, a well-managed network of Marine Protected Areas (MPAs), where human activity is strictly controlled, is one of the best tools we have to protect habitats and species in the face of the profound changes that are already taking place. A well-managed MPA network is good for renewables deployment, as well as for biodiversity, providing certainty to investors and driving improvements in technology to reduce environmental impacts.
One key example of where renewables and MPAs interact is in relation to offshore wind and marine mammals, such as the harbour porpoise. Earlier this year, I blogged about the exciting new set of marine protected areas, identified for this charismatic but shy animal (it was also great to see one of these sites, off the West of Scotland, taking one step towards designation this week!). This was a big win for this species and for our efforts, together with other NGOs, to secure protection for mobile species – which include sharks, rays, whales and dolphins too – as part of a wider network of MPAs.
So it’s now government policy that the proposed sites have to be taken into account when licences for offshore wind are allocated; this means the authorities and developers alike need to understand how the noise produced when installing wind turbines affects the behaviour of harbour porpoises, and what amount of noise is acceptable. You can get a sense of the sound from this video. It’s a series of hammer blows to drive the foundations into the seabed, ready for the turbines to go on top.
Underwater noise affects harbour porpoises in two main ways: at really loud levels, it can cause injury or even death, but thankfully this is relatively rare. Equally importantly though, porpoises and other cetaceans will change their behaviour or avoid areas with even relatively low noise levels, usually for between 1 and 3 days after a noise event. If these events continue, this can lead to the abandonment of the area for weeks, even months. We call this ‘effect disturbance’ if it’s temporary, and ‘displacement’ if it’s longer-term.
In the case of the recently-consented Hornsea 2 wind farm, for example, this meant extra conditions were placed on the developer to demonstrate beforehand how they intened to keep the noise levels down during construction.
One of the objectives of the new protected areas is to avoid any significant disturbance from underwater noise, but this throws up some key questions: how much noise is acceptable? And what benefits do different levels of noise reduction bring? Noise reduction is costly: it can involve altering piling schedules or installing expensive technology to reduce the noise travelling out from the source. It’s therefore vital for both scientists and developers to know what the benefits are of reducing noise by different levels, so that mitigation can be cost-effective.
That’s exactly what our new report, “A Positive Future for Porpoises and Renewables”, written by SMRU Consulting for WWF-UK, aims to do. It uses noise reduction scenarios to identify the benefits of reducing noise by set amounts, against a baseline of no noise reduction at all..
The key finding is that noise reduction really has great benefits for harbour porpoises, and a little goes a long way! If all UK wind farms reduced their noise levels by the equivalent of around 8dB, under the assumptions of the report the risk of a 1% annual decline in the North Sea harbour porpoise population falls by at least 92% and up to 96% up to 2037. These are big benefits for relatively small noise reductions. The scenarios used in the report are based on previously used mitigation technology, even allowing for more challenging UK conditions. Even if these reductions just took place in the harbour porpoise MPA in the North Sea, the risk of a 1% annual decline would still be reduced by up to 66%.
Our research also highlights the amount of offshore wind construction that is planned for the North Sea over the next decade. This is great news, but the North Sea will be a noisy place, and we believe that some form of mitigation for harbour porpoises will be needed inside MPAs to ensure they remain compatible with the site’s conservation objectives. A situation of no mitigation would be doubly unsustainable when you combine the pressure from noise with other pressures, such as fisheries bycatch and pollution.
There are also some useful messages in the report on how other countries deal with underwater noise, which could be useful in current UK discussions. Germany, for example, has a rule that for critical areas for harbour porpoise, 99% of these areas have to be available to porpoise populations in the important summer season. This is significantly stricter than is being currently proposed for the UK sites.
As the first publication to explicitly cover the new MPA for harbour porpoise in the North Sea, our report is a very timely piece of work. We’ll be presenting it to developers and key decision makers over the next few months.Hopefully it will help offshore wind developments to take place inside these protected areas safely, boosting our clean energy supply without reducing our rich and fascinating marine biodiversity.
Ps Reason number 27 why harbour porpoises are brilliant: they were recently been described as “aquatic shrews” and the “animal kingdom’s deadliest hunter” for the way in which they use sound to capture over 500 fish per hour, with a success rate of over 90%. That’s remarkable! It also shows how these animals rely on acoustics to survive.