Can offshore wind farms help to strengthen nature? Organization De Rijke Noordzee is investigating the possibilities. The Gemini wind farm, located above Schiermonnikoog, is the ‘king project’. There, an undersea test field will show whether oysters still thrive as they did in earlier times.
Since 2017, about 55 kilometers above Schiermonnikoog, 150 wind turbines have been producing green energy for about one and a half million consumers. A special test is underway on the seabed of this Gemini wind farm. This should show whether oyster beds can form again. About two centuries ago, they still covered 20 percent of the North Sea floor.
It is an initiative of the organization De Rijke Noordzee, which has been investigating since 2018 whether wind farms can strengthen the undersea flora and fauna. Of the six trials currently running, the one at the Gemini Wind Farm is the largest. Project leader Frank Jacobs: ,,It is our royal project. Our ambition is to create an oyster reef that can sustain itself.”
‘From own conviction’
De Rijke Noordzee works closely with the operator of the wind farm. “We don’t have to do that from the government,” says Luuk Folkerts, responsible at Gemini Windpark for, among other things, monitoring the environment within and near the 68 square kilometers on which the windmills are located. “We cooperate out of our own conviction and interest.”
The year 2021 is almost over when researchers from De Rijke Noordzee lower 1500 oysters and 18 tons of shells onto the seabed, about 30 meters deep, near the wind farm. They will be spread over an area of five hectares, roughly equivalent to eight football pitches. In the autumn of 2022, another 3000 oysters, hundreds of thousands of baby oysters and 48 tons of shell material will be added.
Crabs, squids, sharks and anemones
Oyster larvae attach themselves to a shell to reach maturity. This is how the shells stack up and form a reef. The oyster beds are the habitat for other animals and plants, such as crabs, squid, sharks and anemones. This biodiversity must therefore gradually return to the test field.
Conny Groot, spokeswoman for De Rijke Noordzee: ,,We are now very closely monitoring what is happening. Such research has never been done before.”
Sea chart from 1883
The location was chosen for a reason. A nautical chart from 1883 shows that large quantities of oysters used to lie on the seabed in the surrounding area. Ancient research records testify to the wealth of life around the oyster reefs. Crabs, lobsters and animals with euphonious names such as dead man’s thumb, hydroid polyp and bristle worm felt at home there. Fish species such as the shark and the ray laid their eggs there.
All that life is gone. English and German fishermen landed 10 million oysters annually in the period between about 1880 and 1915. Diseases did the rest. The seabed, with its once rich fauna and flora, is now a submarine sand plain.
The fact that the seabed near Gemini is particularly suitable for the project also has to do with the tranquility of the area.
‘First good news’
Grete Leeuwerik, spokeswoman for the wind farm: ,,For safety reasons, fishermen and tourists are not allowed. In principle, only qualified and trained personnel may come for maintenance. This gives you peace of mind. That is essential for underwater biodiversity.”
Moreover, the northern part of the North Sea has fewer high waves that can move the sand than off the west coast.
An inspection in June showed that this rest is sufficient for the time being. Jacobs: ,,We made videos with an underwater robot. Everything was still there. And there were also crabs and lobsters. That’s the first good news. Soon we will take water samples. We are curious what kind of DNA we will find from, for example, faeces and scales. This way we find out what kind of animals have visited the reef.”
Larvae on the shells
This month, ‘frames’ with shells will also be placed near the reef. Jacobs: “During this period, the seawater has the temperature at which oysters release their larvae. They are looking for a shell to attach themselves to. In about a month and a half we will collect the frames and hope to find larvae on the shells.”
Jacobs hopes that De Rijke Noordzee will gain information through its pilots that the government can use for policy to increase biodiversity in the North Sea. For example, by attaching conditions to the award for the construction and operation of wind farms that stimulate nature.
Fantastic
Folkerts: ,,From Gemini, we would of course think it would be fantastic if an oyster population was created here that would maintain and expand itself. That it can go on without us.”
But what about the recreated piece of nature if after thirty years, in accordance with the permit, the windmills have to be removed and the protection of the area ceases? Folkerts: ,,Society has to think about that. If ten years of fishermen pass, everything will be gone again.”
Groot: ,,We at De Rijke Noordzee are already trying to stimulate that discussion. It would be a shame that a piece of nature that has been developed with so much passion and energy just disappears again when those piles go out of the ground.”
The Rich North Sea is a program of Stichting Natuur & Milieu and Stichting De Noordzee. The initiative was made possible by a contribution of more than 11 million euros from the Dream Fund of the National Postcode Lottery.
‘Effect of Gemini underwater limited’
When the construction of Gemini Wind Farm started in 2014, it would shortly be the largest in the world. Since then, offshore wind has really taken off. Gemini has a capacity of 600 megawatts. If all plans go ahead, the Dutch wind farms in the North Sea will have a combined capacity of 22 gigawatts shortly after 2030. In 2050, the total capacity must be 70 gigawatts. Now that so many wind farms are being built, the question arises what the consequences are for the environment.
‘No idea’
At the time, Luuk Folkerts was also closely involved in the application for the permits for the construction of Gemini. “Nowadays the government produces an environmental impact report for every wind farm,” he says. “We had to do that ourselves. You make an estimate of the effects on the basis of recognized scientific research. But to be honest: we don’t know about many aspects. Before building Gemini, the question was: Would Gemini’s 150 wind turbines affect the current? We had no idea. The change wouldn’t be that big. But what will happen if so many offshore wind farms are built? Then the change can be significant and have consequences for, for example, the growth of algae and plants.”
Birds and bats
The permit for the wind farm obliges Gemini to closely monitor the effect of the wind turbines. Folkerts: “That is a solid ecological monitoring program that focuses mainly on birds and bats. At the wind farm, for example, there are two radars that track their movements. We do counts with airplanes. We also look at whether birds avoid the wind farm. This seems to be the case with auks and guillemots. The question is whether it will stay that way once all those wind farms are there.”
A point of attention are the bats. Folkerts: ,,Surprisingly enough, the shaggy pipistrelle passes Gemini in spring and autumn when she migrates from Denmark to Great Britain. It turns out that if they get the chance, they sleep in the park in the meantime. But we know that bats and windmills are not a good combination on land.”
Bats send out a signal. Based on the echo, they can determine whether there are obstacles in their environment. This prevents them from flying into a mast. However, another problem arises. Due to sudden differences in air pressure caused by the rotating blades of the mill, they suffer internal physical damage (barotrauma).
Folkerts: “We are now investigating whether this phenomenon also occurs at offshore wind farms.”
Limited nuisance under water
According to him, the nuisance for underwater nature is mainly limited to the construction of the wind farms.
“This mainly has to do with the pile-driving of the foundation piles. This creates a sound pressure underwater that can be harmful to animals, especially harbor porpoises. My guess is that you can prevent that by chasing the animals away beforehand with an irritating, but not harmful sound, as we did during the construction of Gemini. Furthermore, the animals do not care much about the windmills. The stone dump (at the foot of the piles – ed.) is teeming with all kinds of animals; lobsters, crabs, starfish… All sorts of things grow on the untreated steel of the foundation. Even the dead man’s thumb, an animal that makes ecologists very happy.”