They might produce renewable energy, but offshore wind farms are a scourge for porpoises. Researchers have found that construction noise at a turbine site off the German coast has scared away the marine mammals, who depend on their acute hearing. A "bubble curtain" could protect the sensitive cetaceans from future stress.

The offshore wind farm Alpha Ventus is a project of imposing dimensions. A total of 12 wind turbines rise from the North Sea in an area of about 4 square kilometers (1.5 square miles). Each one stands about 150 meters (490 feet) high and weighs 1,000 tons. The farm is designed to provide electricity for about 55,000 households.

Now the environmental impact of the massive project, which lies some 45 kilometers (28 miles) north of the German island of Borkum, is becoming clear. Germany's Federal Maritime and Hydrographic Agency (BSH) has completed its first study of the impact of the wind farm -- and found that the racket made by the construction of the site had scared off porpoises living in the area.

To read the rest of this article, click here.