Bottom-Dwelling Marine Animals Thriving on Offshore Wind Farm Foundations

In a discovery by researchers from Leiden University in the Netherlands, offshore wind turbines have become a haven for benthos — the community of marine organisms that live in, on or around the seafloor.

There are more soil animals per square meter living in the foundations of offshore wind farms than on the floor of the North Sea, a press release from Leiden University said.

“The turbine foundations provide hard substrate for settlement in areas where these habitats have never been present before. Except for islands, there are now structures spanning the entire range from sea floor to sea surface,” Jan Vanaverbeke, a postdoctoral researcher at the Royal Belgian Institute of Natural Sciences, told EcoWatch in an email. “A lot of organisms, normally living on hard substrates (rocks, bio- or geogenic reefs) have larvae with pelagic stadia, drifting in the water column and trying to find a suitable place to settle and grow into an adult. The turbines provide such substrate in areas where it has never been present before.”

In the area surrounding the wind farms, fishing is not allowed, meaning fish can flourish.

“Banning fisheries from offshore wind farms has positive effects as (1) wind farms provide a safe place for fish (where some species find a lot of food), and (2) the sea floor is not disturbed and therefore long-living animals have a chance to actually live long (they are not impacted/killed by the fishing gear that is passing),” Vanaverbeke told EcoWatch.

The lifespan of a wind turbine is about 25 to 30 years, so Chen Li, an industrial ecologist and research lead for the study, looked at the effects of wind turbines on the soil after 25 years.

Li discovered that, after a quarter century, twice as many species and a hundred times the number of marine animals could live in the same wind turbine foundations.

Before the study, not much was known about how wind farms affected marine life in the long-term.

“Previous studies focused only on several years, not a whole life cycle of a wind turbine,” Li said in the press release.

The study, “Offshore Wind Energy and Marine Biodiversity in the North Sea: Life Cycle Impact Assessment for Benthic Communities,” was published in the journal Environmental Science & Technology.

The study showed that wind turbine foundations are preferred by soil animals over the floor of the North Sea. Scientists were aware that these animals were comfortable in wind farms, “but now we have detailed numbers and a method to quantify the effect of wind farms on biodiversity,” Li said.

“It is great that, along with the contributions of offshore wind energy to renewable energy, there can also be co-benefits for marine biodiversity,” said Laura Scherer, an environmental scientist and co-author of the paper, in the press release.

For the study, Li used data from samples of seabed life collected on six Dutch, Danish, Belgian and German wind farms over a period of up to 11 years. The data was from Ghent University, the Wageningen Marine Research institute and the Royal Belgian Institute for Natural Sciences.

Li compared the samples of marine life taken from just outside the wind farms with those taken inside the farms, then used a model to approximate the development of the marine animals until the end of the lifespan of the wind turbine.

Despite positive results for some sea creatures, the presence of wind turbines is not beneficial for all marine life.

“It depends on which species are lost or gained. An advantage for one species can be a disadvantage for another,” Scherer said in the press release.

The wintering or feeding grounds of some seabirds who steer clear of wind farms can be lost, for instance.

Building wind turbines can also disrupt wildlife, but this was not considered in the study.

“Installing a turbine creates a lot of vibrations and noise,” Li said in the press release.

Mammals and fish can be disoriented by these disruptions.

When a wind turbine reaches the end of its lifespan, what happens to the marine creatures who have made their home there?

“This depends on the decommissioning scenario: if the turbines are removed entirely, the associated communities are removed. If they are replaced, the expectation is that they will return. The question is whether this removal is a problem, because at some places, the additional diversity is artificial (not related to what can be expected in a natural situation),” Vanaverbeke told EcoWatch.

Scherer is “cautiously optimistic” about the effects of the growing number of North Sea wind turbines on biodiversity, “if the locations are carefully chosen.”

“[W]hen the new artificial habitat is designed according to the nature-inclusive design principle, there is a chance to combine the introduction of wind farms with conservation efforts,” Vanaverbeke told EcoWatch.

Steps can be taken to mitigate some of the harm caused to animals and ecosystems in the installation of wind turbines.

“If we talk about benthos, then the adverse effects are small. There is a loss of habitat (underneath the turbine and the scour protection layer — if present), and some disturbance during construction. The benthic fauna recovers quickly from the disturbance,” Vanaverbeke said. “The construction phase can come with adverse effects for sea mammals, can be mitigated by an informed choice of the period of construction (when presences are low or sea mammals generally low) or noise mitigation measures (bubble curtains, sea mammal observers… ). There can be negative effects on sea birds or migratory birds. Mitigation can be in providing corridors, avoiding foraging areas, or stopping the turbines in periods of mass migration.”

The overall positive effects of the renewable energy produced by wind farms on climate change can benefit marine life.

“[E]ven if there were net negative impacts of the infrastructure and operation of offshore wind power, the benefits from less climate change could possibly compensate for them,” Scherer said in the press release.

Do the benefits of wind turbines for benthic species and the renewable energy produced by wind farms in reducing climate change for animals overall outweigh the negative impacts of the installation and operation of offshore wind farms on certain species?

“Climate change will have global impacts on species, changing distributions, behaviour and possible interactions. The effect of infrastructure is local (and indeed regional, as there are multiple wind farms with cumulative effects). My feeling is that a smart, science-based location of offshore wind farms, where ecological principles are incorporated in the design is needed to combat climate change,” Vanaverbeke told EcoWatch.