Article Source: IMechE

Around the world, there are more than 7,500 oil and gas platforms and between 10,000 and 20,000 wind turbines that will need to be removed when they come to the end of their working lives.

It’s been estimated that the removal – which is mandated by international convention – will cost up to €100bn.

But now a group of almost 30 international researchers are making an unlikely call to halt the decommissioning of old oil rigs, wind turbines and other offshore installations. Oil rigs and other artificial installations are typically present for 20-30 years in the sea. Through this period, the tubes, bars, concrete bricks and much more turn into beneficial substrate for adhering plants and animals. And this rich environment attracts fish and mammals.

“In, for example, the North Sea, an old oil rig will have the same function as a natural stone reef,” explains Jonas Teilmann, a senior researcher from Aarhus University in Denmark, who has been involved in the studies that were published in the international journal Frontiers in Ecology and the Environment. And stone reefs are in short supply as stones have been removed and used for, among other things, pier construction or been destroyed and spread owing to the use of heavy trawls.

Biodiversity boosted

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

A submerged camera at an old worn-out oil rig in the North Sea shows an extensive life of flatfish, cod and bottom fauna in all its forms – species usually not seen in those areas. “We also see many more porpoises around oil rigs than in the surrounding sea,” says Teilmann.

“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 says.

Perhaps money can be saved and conditions for marine life improved by leaving structures in place. “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,” says Teilmann.

Call a halt to removals

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. According to the researchers, the competent authorities should instead make an environmental assessment of which structures to leave and conduct follow-up investigations of the effect of the new reefs.

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