Vindkraftverk till havs.
Photo: JEAN SCHWEITZER/Most Photos

Researcher: “Marine life benefits from offshore wind power”


Biodiversity increases and more fish appear in the waters around offshore wind farms. This is according to a review of over two thousand scientific articles on the subject done by Thomas Dahlgren, a researcher in marine ecology at the University of Gothenburg.

Offshore wind farms have become a hot topic in the wake of high energy prices and increased demand for fossil-free electricity. But what’s the impact on marine life? Thomas Dahlgren has been working on the environmental effects of offshore wind power for 15 years, both in Sweden and Norway. 

“Few activities at sea are as well studied as the environmental impact of wind farms. When we summarise the research that has been done, it’s clear that the positive effects on marine life outweigh the negative ones,” he says. 

One of the issues discussed is that fish are negatively affected by offshore wind farms. Thomas Dahlgren therefore highlights a study compiling hundreds of different reports that shows that both the quantity of fish, and the number of fish species, increase around an offshore wind farm. According to the study, an important reason for this is that fishing with bottom trawls it’s not possible around offshore wind farms.

“Bottom trawling has a major impact on the biological life in the sea. Apart from the obvious loss of fish as a result of fishing, bottom trawling also damages the seafloor and makes bottom-dwelling animals, such as sea pens and soft corals, disappear from the area. When bottom trawling isn’t possible, these species could return to the area,” says Thomas Dahlgren. 

Thomas Dahlgren porträtt.
Thomas Dahlgren är forskare i marinbiologi på Institutionen för marina vetenskaper vid Göteborgs universitet och Norwegian Research Centre i Bergen.

Form artificial reefs

Another important reason why fish increase in the area is that the foundations of the wind turbines have hard surfaces that form artificial reefs, where sessile species such as corals and sponges can find places to live, something that is usually scarce on the muddy seafloor. 

“These foundations create an environment where fish gather to find shelter, feed, and reproduce. The artificial reefs contribute to the increase of biodiversity in the area,” says Thomas Dahlgren. 

The biggest negative impact on marine life occurs during the construction phase. When the wind turbines are anchored to the seafloor, the water becomes clouded and noise from the construction could disturb some marine animals, such as porpoises. The extent of the disturbance depends on the type of wind turbine, but the disturbance only occurs for a limited time.

“Underwater noise is an issue when installing a particular type of foundation, but avoiding installation during seasons when species and ecosystems are sensitive could limit the impact. In an operational wind farm, no negative noise impact has been shown,” says Thomas Dahlgren.

Seabirds are affected

Another argument put forward in the debate is that turbine blades release plastic and thus contribute to microplastics in the sea. But according to Thomas Dahlgren, no scientific studies have been able to present wind farms as a significant source of microplastics in the sea.

“Instead, the major sources of microplastic emissions are from boat bottom paints, plastic litter, and fishing gear. Land-based emissions, such as wear and tear on car tyres and textiles, are also important sources of microplastics in the sea,” he says. 

There are also concerns raised that birds could be affected by wind farms. Research shows that some bird species avoid them, such as the long-tailed duck and the common eider. Therefore, it’s important that wind farms aren’t located in places that these species depend on, such as mussel beds in the Baltic Sea. There’s also a risk of migrating birds colliding with the turbine blades.

“I’m not an expert on birds, and therefore I can’t comment on the state of knowledge in these cases, but wind power operators are already today required to stop the turbines when there are sensitive species in the vicinity,” says Thomas Dahlgren.

Is there anything that needs more research?

“Yes, more knowledge is needed about how several wind farms put together affect ecosystems on a regional scale. But it’s difficult to investigate that before more wind farms are in place.” 

Text: Karl-Johan Nylén

Translation: Annika Wall