A new review carried out by biodiversity experts at the UN Environment Programme World Conservation Monitoring Centre (UNEP-WCMC) has found that offshore wind energy developments have a range of both positive and negative impacts on underwater animals that migrate – including whales, porpoises, seals, various fish and crustaceans.

The review shows that overall effects of offshore wind infrastructure on migratory species tend to be negative, especially during the construction phase. Its authors call on industry stakeholders to consider these impacts as early as possible when designing and installing new infrastructure, and to factor mitigation into planning and development processes. However, there are also instances where positive impacts have been observed, particularly with regard to some fish populations that benefit from the refuge provided by the new infrastructure.

Importantly, the review identified significant knowledge gaps – both in terms of species and also relating to wind farm types, operations and locations. The briefing’s authors emphasise that a lack of research does not equate to no impact; therefore, these findings and the gaps identified present a window for further exploration and potential opportunities for new approaches in conservation, restoration and sustainable management.

UNEP-WCMC’s experts reviewed 68 studies that evaluated the impact of offshore developments during wind farm construction and operation. Most of the studies (53) assessed wind farms in Europe, three-quarters of which were in the North Sea.

With offshore wind developments expected to grow six-fold by 2030, there is an urgent need to understand the range of impacts these projects can have and mitigate negative impacts as far as possible. Taking such action is good for business, as it can minimise financial, regulatory and reputational risks. It also helps to future-proof operations, as organisations incorporating biodiversity-conscious measures will be more likely to benefit in a sustainability-focused landscape. The sustainable management of wild species, biodiversity-inclusive spatial planning and conservation of marine areas are all important elements of the Kunming-Montreal Global Biodiversity Framework, which sets out key global targets for countries to contribute towards with the aim of achieving the vision of living in harmony with nature.

The majority of research exploring the impact of offshore wind projects upon marine migratory species focused upon the harbour porpoise, the harbour seal, the grey seal and Atlantic cod. However, the research shows that a wide range of bony fish species beyond cod are impacted, including whiting, Atlantic herring and Chinook salmon – with both negative and positive impacts recorded. As these are significant species for commercial fishing, this could potentially have considerable implications for food security and the blue economy.

How does offshore wind impact migratory species?

The review found that offshore wind energy has a wide range of negative impacts on marine migratory species. These can be grouped under the following categories:

• Behavioural – such as displacement, changes in migratory route and time, or avoidance. Behavioural impacts were the type most commonly observed across the research
• Environmental – this includes species abundance or absence and diversity levels
• Acoustical – this covers masking or changes in vocal pattern
• Physical – for example stress, hearing loss, injury or even fatality

Avoidance was shown to be the most common negative impact, exhibited primarily among mammals during the construction process.  

Bony fish such as cod were shown to be primarily impacted during wind farm operation as opposed to construction, with notable negative impacts being changes in swimming pattern and alterations to migratory routes and timing. However, it was also during the operation phase that positive impacts were observed for these species, including increased abundance and species presence. This was due to the foundations of wind farms serving as new habitats for the species. 

The briefing points out that there are gaps in the research regarding the different stages of an offshore wind farm’s development; for example, there were fewer studies focusing on the construction phase than the operation phase in relation to bony fish. Furthermore, only eight per cent of the marine migratory species listed under the UN Convention on Migratory Species were covered in the reviewed studies. This is partly due to a focus on studies written in English and geographical bias towards European waters owing to the historical prevalence of wind farms in this region.

This work fills a knowledge gap by providing an overview of current understanding of offshore wind in relation to marine migratory species, and suggests how companies involved in the sector can reduce and manage these impacts.

Our review found that the majority of studies have been conducted in Europe. However, with China now the largest offshore wind market and North America deploying large offshore projects, there is a significant knowledge gap for these regions. We need more research to fully understand the range of impacts of offshore wind and how to mitigate the negative aspects.

Sebastian Dunnett, Senior Programme Officer, UNEP-WCMC

What can be done to minimise negative impacts?

Although the briefing identifies gaps in the research, it’s clear that these should not be a reason to delay action on reducing the negative impact of operations. The authors identify practical steps that can be taken by businesses to achieve this, and suggest following the Mitigation Hierarchy when launching new projects.

The briefing emphasises that preventative measures will be the most effective in reducing both economic and ecological impacts, so businesses are advised to consider mitigation – particularly the avoid and minimise steps – as early as possible in the development process. For example the timing of construction of offshore wind infrastructure could be scheduled to avoid peak periods of marine mammal migration through the area. Other recommendations such as increased data sharing and collaboration are also put forward.

With offshore wind energy expanding at a rapid pace, there is a need not only to address immediate concerns for marine migratory species, but also to gather more data to deepen understanding of possible impacts. This should ideally encompass all kinds of offshore wind infrastructure. For example, just one of the reviewed studies examined floating offshore structures; this fledgling industry will only continue to grow, so it’s vital that further research into this area is conducted. Decommissioning is another under-studied area in terms of impact on migratory species, as very few offshore wind farms have reached the end of their operational lifetime, but this is likely to change over the next decade. Where data does exist, it’s vital that this is shared among stakeholders across the seascape, and if possible made open and publicly accessible. Collaboration across sea users and researchers is vital.

The negative impacts on migratory species highlighted by the review are cause for concern. However, its authors suggest that there is an opportunity to develop offshore projects that go beyond mitigation and enhance positive impacts, thereby achieving positive outcomes for nature and people.

Download the full review here.

This briefing was produced under the Proteus Partnership, a UNEP-WCMC engagement which convenes a cross-sector group of businesses with the data, knowledge and expertise they need to make better informed decisions and address biodiversity challenges. To find out more, click here.

Main image: Nicolas Job / Ocean Image Bank