Animals at risk

Families walk their dogs along the sandy beach, the waves lapping to their side, oblivious to the fact that less than 100 kilometers (62 miles) off the coast wind turbines turn creating energy for electricity in tens of thousands of German homes.

Such renewable energy is a key element in Germany's transition away from coal and nuclear energy, but now some are questioning the environmental impact of offshore wind farms particularly on animals – in both the sea and air.

"There are indications from research that fish larvae can be damaged by intense sounds,” said Fabian Ritter, leader of the marine protection campaign at Whale and Dolphin Conservation in Berlin.

"Seals are very sensitive to sounds and can be easily disturbed," he told DW. "There's disturbance and the risk of collision for birds, and bats, and other animals."

Increase of biodiversity

A recent report released by Germany's Federal Maritime and Hydrographic Agency, known as the BSH, on the wind farm Alpha Ventus has sought to soothe conservationists' fears. According to the report, the effects on fish, birds and marine mammals are minimal.

Conducted over five years, the study looked at the ecological effects of the 12 turbines at Alpha Ventus, a test site run jointly by energy firms EWE, E-ON and Vattenfall, 60 kilometers off the German coast in the North Sea. It revealed an increase in the biodiversity at the bases of the turbines.

"Life on the ground had very much intensified because small life-forms such as mussels, starfish and sea anemones, were able to find a new surface on which to grow and multiply, much stronger than on the sand that was already there," said Monika Breuch-Moritz, president of the BSH.

"That is actually just a normal result, you see similar things on every shipwreck," she told DW.

Hearing loss for animals

Although there are still concerns about birds getting stuck and killed while flying across the path of the massive wind turbine blades, one of the biggest concerns for conservationists relates to harbor porpoises, mammals which depend on their sense of hearing to hunt and navigate. According to the report, the animals were at times driven up to 20 kilometers from the sound of construction.

"If sounds become too intense, there's going to be severe damage to the harbour porpoise,” said Ritter. “If they become deaf, that's a death sentence for them."

Companies are required to limit noise to 160 decibels – the same level of noise as a jet plane taking off – at a distance of 750 meters away from construction sites. The German environment ministry also implemented new requirements in December as part of a noise prevention concept. Guidelines require measures such as bubble curtains, where air bubbles are released from the seabed to create a sound-insulating barrier.

While Breuch-Moritz said the move was important, she added that the study had found porpoises returning to the site following the end of construction.

"As soon as the pile-driving is over, the porpoises come back," said Breuch-Moritz. "The operation of a wind farm, not the construction, doesn't disturb the porpoises."

Cumulative effects

Still, conservationists say the report does not take into account the cumulative effects of the many wind farms being built off Germany's north coast and say the noise prevention concept, which is only in effect for the North Sea, should be extended to also cover the Baltic Sea.

According to the German Offshore Wind Energy Foundation, which works closely with the German environment ministry, offshore wind turbines generated 520 Megawatts (MW) of electricity in September 2013. The government plans to increase that figure to 25,000 MW by 2030.

"We're not talking about one site, but hundreds over decades," says Fabian Ritter. "You could say you are changing an ecosystem, sound-wise."

Even so, Andreas Wagner, manager of the German Offshore Wind Energy Foundation's Berlin office, which worked with the energy firms to build the Alpha Ventus wind farm, said there was a lot of effort being taken by industry to reduce the potential ecological impacts.

"We have more than half a dozen commercial offshore wind farms under construction right now, but they are not all being built at the same time and not installing the foundations at the same time, so there are not many cumulative effects in reality," he said.

Many conservationists say they do not want to see less development in the sector of offshore wind energy, but greater consideration of the potential effects of offshore wind farms.

"We think it's the future of the energy development in Germany and maybe in Europe and worldwide," says Fabian Ritter, from the Whale and Dolphin Conservation organization. "But you have to look at what you can do to minise harm to the marine environment."