According to biologists, the expansion of wind energy in the North and Baltic Seas poses an increasing threat to migratory birds. To protect them, the Netherlands have stopped wind turbines in their wind farms off the coast for the first time.
The offshore wind turbines in Borssele and Egmond aan Zee were shut down for four hours on Saturday because massive bird migration was predicted over the North Sea, the government said on Monday.
“This is an international first,” said Dutch Energy Minister Rob Jetten. Nowhere else in the world would wind farms in the sea be switched off to protect the birds. The government wants to keep the impact of wind farms on nature as small as possible.
Model predicts bird migration two days in advance
The wind farms are expected to be shut down more frequently from autumn 2023 after the pilot phase that is now underway, it said. In order to allow birds a safe passage, the wind farm owners should reduce the speed of the wind turbines to a maximum of two revolutions per minute during the predicted nocturnal migration time.
This very slow speed is almost like a complete standstill “for us and the birds”, explained Pieter ten Bruggencate, spokesman for the Ministry of Economy and Climate. The government also explained that future wind farms must also comply with the measure, the effectiveness of which is constantly being checked.
At the end of 2022, a doctoral student from the University of Amsterdam presented a model that uses weather data, among other things, to predict bird migration two days in advance.
This should give the grid operator Tennet time to ensure the stability of the high-voltage grid and to initiate the shutdown of the turbines.
According to the government announcement, bird protection expert Tim van Oijen said: “Twice a year, in spring and autumn, millions of birds migrate across the North Sea on some nights.” Because of the increasing number of wind farms there, it is extremely important that this expansion has minimal impact the ecosystem of the North Sea.
Twice a year, in spring and autumn, millions of birds fly over the North Sea on some nights.
Tim van OijenDutch bird protection expert
In Germany, too, the planned strong expansion of wind energy on the North Sea and Baltic Sea represents an increasing danger for migratory birds, according to biologists. There are currently 22 wind farms in the North Sea and three in the Baltic Sea off the German coast, with a total capacity of 8 .1 gigawatts.
By 2030 it should be 30 gigawatts, by 2045 the total output should be increased to at least 70 gigawatts according to the offshore wind energy law that came into force at the beginning of the year.
Scientists from the Research and Technology Center West Coast of the Christian-Albrecht University in Kiel studied the reactions of Curlews and Sea Geese to wind turbines during their migration from the Wadden Sea to Northwest Russia.
For the international study, the researchers captured 143 curlews, 30 brent geese and 87 barnacle geese and fitted them with small transmitters. The GPS devices provided movement data for six years, as study leader Philipp Schwemmer reported on Tuesday at the Marine Environment Symposium of the Federal Maritime and Hydrographic Agency in Hamburg.
The recordings showed that about 70 percent of the curlews soared in front of the turbines or changed course to avoid the turbines. “First of all, this is good news, because the majority of the animals apparently avoid collisions,” explained Schwemmer.
However, he added: “About 30 percent of curlews pass through wind farms without reacting.” This poses a risk for the animals. The curlew is one of the endangered species.
In the sea geese, the data showed a clearly defined migratory corridor between the German Baltic Sea, southern Sweden and the Gulf of Finland, which the animals use on their way to northern Siberia on only a few days a year. Whether sea geese also avoid the wind farms is still unclear. However, around 90 percent of the animals fly at the height of the wind turbines.
Schwemmer called for this corridor to be taken into account when planning offshore installations or for the installations to be switched off on the few days when birds migrate. The study will soon be published in the journal “Journal of Environmental Management”. (dpa, AFP)
