11th July 2018

Oil rigs may end their days as valuable artificial reefs

A group of international researchers have just published a scientific article in which they encourage environmental authorities across the globe to rethink the idea of removing oil rigs, wind turbines and other installations in the sea when they are worn out.

A submerged camera at an old, worn-out oil rig shows an extensive ecosystem of cod, flatfish, bottom fauna and other marine life. A life that is not usually seen in these parts of the North Sea, where the rig awaits decommissioning after 25 years' of service in pumping oil and gas from the ground.

"We also see many more porpoises around oil rigs than in the surrounding sea," says Jonas Teilmann, senior researcher from Aarhus University, who has been involved in studies published by the international journal Frontiers in Ecology and the Environment. "It's easy to understand why the porpoises enjoy the area. One can't throw a fish hook without catching one of the many cod around the legs of the oil rig," he adds.

An oil rig or other artificial installations are typically present for 20 to 30 years in the sea. Through this period, the tubes, bars, concrete bricks and other components turn into beneficial substrate for adhering plants, becoming a rich environment for fish and mammals.



Credit: Jon Svendsen

Internationally, it has been decided that that all artificial installations in the sea must be removed when they are no longer in use. But now, a group of almost 30 international researchers say that this decision perhaps should be reconsidered.

"In, for example, the North Sea, an old oil rig will have the same function as a natural stone reef," Jonas Teilmann explains.

And stone reefs are in short supply, as stones have been removed and used for, among other things, pier construction. Many have also been destroyed and spread due to use of heavy trawls.

"We have observed a significantly increased biodiversity around the old facilities and encourage authorities to consider, in each individual case, whether an exemption from the demand for removal can be granted," says Teilmann. "When making the assessment, the environmental conditions must, of course, be of sufficient quality."



Map of the northern Gulf of Mexico showing the locations of thousands of oil and gas platforms. Credit: U.S. National Oceanic and Atmospheric Administration

Around the world, there are more than 7,500 oil and gas platforms and between 10,000 and 20,000 wind turbines that need to be removed at some point. It is estimated that it will cost up to €100 billion ($117 billion) to remove all these installations. But perhaps, instead, the money could be saved and the conditions for marine life improved.

"By leaving the rig in place, we may ensure greater biodiversity in the sea. The physical structures also ensure that the areas will not be trawled. The heavy trawls turn the seabed into a uniform desert with poor biodiversity," explains Teilmann.

The research group behind the article therefore urges politicians and officials throughout the world to introduce a temporary halt on the mandatory decommissioning of offshore infrastructure. An environmental assessment should be made for which structures to leave, with follow-up studies to investigate the effect of the new reefs. In the decades ahead, this could help to restore a significant amount of biodiversity in the world's seas.



Credit: D. Jones

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