Abstract
As huge offshore wind farms spread across Europe's North and Baltic seas, efforts grow to buffer the impact on wildlife.
Over the past decade, a curious invention has spread across Europe's northern seas. It's called a big bubble curtain, it works a bit like a giant jacuzzi, and it helps protect porpoises from the massive underwater noise caused by wind farm construction.
A very large, perforated hose is laid on the seabed, encircling the wind turbine site. Air is pumped through, and bubbles rise from the holes to the surface of the water, forming a noise-buffering veil.
The quirky gadget, also known as a big bubble veil, was pioneered in Germany to help protect the endangered harbour porpoise, the only cetacean species living in its North Sea and Baltic Sea. The bubble curtain was designed around the porpoise's specific needs and traits, lowering wind farm construction noise to a threshold deemed safe for the species, based on scientific research. Its proven muffling effect may also benefit other marine mammals that are vulnerable to noise, such as seals.
The bubble curtain is now widely used by northern European countries racing to build more offshore wind farms as part of their efforts to curb CO2 emissions and fight global warming. Countries including the Netherlands, Germany, Denmark and Belgium have pledged to turn the North Sea into "the world's largest green power plant", aiming to jointly increase their offshore wind capacity there to 300GW by 2050. At the same time, they are under pressure to reduce the potential impact of wind farm construction noise on marine creatures, for whom sound is everything.