How do offshore windfarms affect biodiversity? | Marine@Ugent

How do offshore windfarms affect biodiversity?

What is the current state of offshore windfarm industry?

At the end of 2020, 394 wind turbines were operational in a total of 8 offshore windfarms in the Belgian part of the North Sea, or our 11th province as it is sometimes referred too. These wind farms are located near the Dutch border, spanning an area of 238 km². Their power corresponds with ~10% of the Belgian electricity demands, or 50% of the domestic electricity demand. In the next few years, a second construction phase will start at the border with the French part of the North Sea. For this Princess Elisabeth concession zone, another 281 km² is reserved for the construction of offshore windfarms. This should double the contribution of offshore wind energy to the Belgian electricity supply.


How does the construction of these offshore windfarms affect marine biodiversity?

The Belgian part of the North Sea is one of the busiest in the world. We have to combine a diversity of functions on a small geographical area: nature conservation, renewable energy, fisheries, sand extraction, dredging, shipping, military exercises, … The construction of windfarms on land instead of at sea, appears difficult. Only few people tolerate wind turbines in their backyard. In addition, wind force at sea is stronger. The current offshore windfarms have been constructed on sandbanks which naturally harbour relatively poor seafloor communities (clams, worms, small crustaceans), due to their dynamic nature, with strong currents and low food availability.

Of course, these ‘naturally poor seafloor communities’ in the Belgian part of the North Sea have to be considered within their historical context: the communities were indeed relatively poor in the last century, but this is due to large scale extraction of oyster banks that covered vast areas of the North Sea until the end of the 19th century.

Back to the current state: the offshore windfarms can lead to an increase in biodiversity below the sea surface. The presence of the turbines alters the water currents  and resuspension patterns of the sandy seafloor. Our Belgian part of the North Sea barely harbours hard substrates (except for gravel beds and ship wrecks). The seafloor here exists mainly of sandy substrates. Hard substrate fauna such as the blue mussel, anemones and tube building amphipods (crustaceans) therefore find the turbines a suitable place to attach to and now colonize the turbine foundations massively. These communities filter plankton and increase the food availability for other organisms. In addition, the shipping restrictions in the offshore windfarms make them a de facto marine protected area, as in these concession zones, shipping including fisheries is not allowed. Fish species such as cod and pouting have been shown to take shelter between the turbines, but also feed on the higher number of seafloor-inhabiting clams and worms.

Figure 1: Offshore wind farm structures provide habitat for invertebrate organisms that foul the foundation along the depth gradient and attract predator fish, seabirds, and marine mammals. Illustration by Hendrik Gheerardyn. From: Degraer et al. (2020) Offshore wind farm artificial reefs affect ecosystem structure and functioning. A Synthesis. Oceanography 33 (4) pp. 48-57.


Have the offshore windfarms been constructed in a nature-inclusive way?

I don’t think that the nature inclusiveness of offshore windfarms has been considered in the first construction phase. The monopiles, the type of foundation that is currently used most often, is being driven in the seafloor and large rocks are placed to stabilise the turbine and protect it from erosion processes. It appears now that this erosion protection layer attracts many fish species, but this increase in local biodiversity was, to my understanding, a nice add-on.

In the second construction phase in the Princess Elisabeth zone, nature inclusiveness has been placed on the agenda, in particular the type of substrate that will be used for the erosion protection layer. This should allow at least the maintenance of local biodiversity, or, in the best case scenario, the promotion of it. This is important, because the new concession zone for the next offshore windfarms overlaps with an area placed under EU Natura 2000 conservation measures, for its gravel beds that constitute a brood chamber for many rare species.


How is Marine Biology Research Group working together with researchers, industry and government to provide the best possible science to build and monitor the effect of our offshore windfarms? Can you tell us why collaboration is important?

The Marine Biology Research Group coordinates the monitoring of the sediment and the fauna associated with this sediment. This is part of a large integrated monitoring of the effects of offshore windfarms, coordinated by the Royal Institute of Natural Sciences and including partners from ILVO and INBO, spanning different ecosystem components (marine mammals, (sea)birds, fish and benthic invertebrates) at various spatial scales (wind farm-scale, turbine-scale and microhabitat-scale). This collaboration is important to get an ecosystem view on the effect of offshore windfarms on the marine realm.

In addition, we collaborate in different nationally-funded research projects investigating how offshore wind farms affect marine food webs and carbon sequestration. These collaborations are often cross-disciplinary, involving oceanographers, biologists and ecosystem modellers. Therefore, they are crucial to get an integrated view on their influence on important ecosystem services such as food provisioning and carbon sequestration. Our findings are communicated to policy, offshore wind industry and environmental NGO’s through our annual reports and public events where we present and discuss our results with different stakeholders. Our last event took place online in June 2021, but we look forward to a live interaction next time.


Author: Ulrike Braeckman, Post-doctoral Researcher at the Marine Biology Research Group
Phone: +32 9 264 85 34
More information on monitoring is available via
Degraer, S., Brabant, R., Rumes, B. & Vigin, L. (eds). 2020. Environmental Impacts of Offshore Wind Farms in the Belgian Part of the North Sea: Empirical Evidence Inspiring Priority Monitoring, Research and Management. Series ‘Memoirs on the Marine Environment’. Brussels: Royal Belgian Institute of Natural Sciences, OD Natural Environment, Marine Ecology and Management, 131 p link