Development at sea

How we use our seas

Development at sea

Dave Dunlop

Part of nature's recovery

We believe that development at sea should be environmentally sustainable. It should do as as little harm to the environment as possible regardless of what the development is. Development should take place using the right technology in the right place and make a positive contribution to nature’s recovery at sea.

Why is it important?

Our seas need to be managed to recover from past damage, disturbance and neglect. With the demands on our seas for resources and energy, the scale of future development is increasing. Future development needs to take place in a sustainable way to allow nature’s recovery within our seas to take place. Offshore renewables, particularly offshore wind, is a fast-growing industry. Although producing green energy, the construction of offshore wind farms has environmental impacts like any other marine development. Impacts can include loss and disturbance to habitats and species. In particular we are concerned about the impact of underwater noise from construction on marine mammals, which are particularly sensitive to noise.

What The Wildlife Trusts are doing

Due to the scale of offshore marine renewable developments, we are engaging closely with this sector. The impacts from the scale of developments, especially offshore winds, are not fully understood. We engage on individual developments through the life span of the project to ensure minimal impact on the marine environment. We engage closely with government, regulators and statutory nature conservation bodies to influence policy at a national level.

Our work also focuses on the impacts of underwater noise from the construction of offshore wind farms. Construction can cause large levels of noise to radiate into the marine environment. This has the potential to cause injury and disturbance to marine mammals. We believe noise reduction plans should be implemented at a whole seas level.

Three examples of our work

Offshore wind farm cables avoid one of the most important chalk reefs in Europe

The Wildlife Trusts have successfully worked with two offshore wind farm developers who are bringing cables onshore in Norfolk, to avoid the chalk reef within Cromer Shoal Chalk Beds Marine Conservation Zone (MCZ).

Located just 200 metres from the Norfolk coast, this unique chalk reef system is one of the best examples of subtidal chalk in the North Sea and forms part of the largest chalk reef in Europe, and possibly the world. Marine life is abundant within the MCZ. There are blue mussel beds, harbour porpoises, grey and harbour seals, sunfish and basking sharks. At least 350 different species have been recorded within the MCZ by volunteer dive surveyors. 

The subtidal chalk within the MCZ provides a unique habitat to a diverse range of species. Slight changes to the chalk environment could reduce the biodiversity of the species reliant upon this habitat. The proposed cable routing through the chalk reef would have resulted in permanent loss of part of this unique habitat.

This success story highlights our approach to working with offshore wind farm developers at an early stage can result in a win win for everyone involved. We continue to work with offshore wind developers to ensure that the right technology is used in the right place.

The Wildlife Trusts set a precedent for future offshore wind farms

In August 2016, planning permission was granted for Hornsea Two offshore wind farm. The Wildlife Trusts was named as a consultee for marine mammal mitigation. We felt it was essential to be a named consultee for two reasons:

  1. Offshore wind farms produce large amounts of underwater noise when constructing the foundations for offshore wind turbines. This has the potential to injure and disturb marine mammal.
  2. There was a lack of detail on underwater noise management to reduce impacts when planning permission was granted.  This detail would be developed many years later, near to the time of construction.

The naming of The Wildlife Trusts on the planning application for this offshore wind farm is significant. It allows us to influence the development of marine mammal mitigation for Hornsea Two offshore wind farm, ensuring the best possible management is put in place. 

The Wildlife Trusts continue to engage with a range of offshore wind farm developers and have places on a number of project marine mammal expert working groups. We also work with government to ensure the best policy is in place to reduce noise impacts from offshore wind farm construction. 

The Wildlife Trusts secure better management of Dogger Bank SAC

In 2015, we began judicial review proceedings regarding the approval of Dogger Bank Teesside offshore wind farms. This was due to fisheries being left out of the wind impact assessment. 

Dogger Bank is a large glacial sandbank situated 62 miles from the English coastline. Formed during the last ice age, it was part of ‘Doggerland’ which connected Britain to mainland Europe. The sandbanks are home to an interesting range of species living both on and in the sand. Although well offshore, this sandbank is home to the fish that feed us and the harbour porpoises, dolphins, whales and seabirds that we enjoy seeing along the east coast.

Unfortunately, Dogger’s sandbanks are currently considered to be at unfavourable condition. The biggest driver of this declining ecological health is fishing. Add to this the impacts of aggregate dredging, oil and gas extraction and now the construction of over 800 wind turbines – and you can understand our concerns.

Following our action, the government gave assurances that management of fisheries would be taken forward for Dogger Bank SAC and that fishing would be included in future offshore wind impact assessments. We were delighted with this outcome. However, we are still seeing the exclusion of fisheries in cumulative impact assessments and we continue to work with government resolve this issue.

Harbour Porpoise

Harbour Porpoise ©Niki Clear

The scale of offshore wind development

Offshore wind farms are not simply ‘onshore wind farms at sea’; they are on a much larger scale. A single onshore wind turbine has a capacity of around 2.5 MW and the average size of an onshore wind farm is only 7 turbines. The offshore wind farm projects applying for planning permission are looking to use wind turbines with a capacity of up to 20 MW each and each project could have an average of 300 turbines. The largest of these projects will cover an area nearly five times the size of Hull. 

Impact of noise

Marine mammals are particularly sensitive to underwater noise during the construction phase of offshore wind farms. We believe noise should be consistently managed for whole seas e.g. the North Sea. Due to the pressure from offshore wind farm development, our work at present focuses on the Southern North Candidate Special Area of Conservation (cSAC). This site protects harbour porpoise, as this species is particularly sensitive to noise.

Offshore wind farms are constructed using piling; this is essentially a large hammer which drives the foundations of the turbines into the ground. The noise can cause injury to harbour porpoise within close proximity to the turbines. Disturbance noise can also travel up to 26 km from the point of construction. 

Harbour porpoise use echolocation to detect their prey, predators and mates. Very loud noises can interfere with their ability to echolocate.  This is a particular issue as harbour porpoise which feed constantly and need to consume up to 10% of their body weight per day. If noise stops a harbour porpoise’s ability to find food or stops them from accessing good feeding areas, they can only survive a few days. This will not only have an effect on an individual animal but on a population.

Marine planning

Humans use the sea in a variety of ways. From fishing, to aggregates, to recreational use we make huge demands on the marine environment. Marine plans aim to set out the sustainable use of our seas. The Marine Management Organisation is responsible for the creation of marine planning. Currently there are 10 marine plan areas and it is expected that marine plans for each area will be in place by 2021. 

We believe more could be achieved through marine planning. We want to see a regional seas marine spatial planning programme. This would create wildlife areas, resource areas and sustainable fishing areas. Read The Way Back to Living Seas to find out more.