The grey steel girders of Platform Holly rise 235ft (72m) above the waters of the Pacific Ocean, just a couple of miles off the Santa Barbara coast. Above the water, this decommissioned oil rig is dull and lifeless, but the view below the surface is very different. Beneath the waves, colourful fish, crabs, starfish and mussels congregate on the huge steel pylons, which stretch for more than 400ft (120m) to the ocean floor.
There are more than 12,000 offshore oil and gas platforms worldwide. As they drain their reservoirs of fossil fuels below the sea, they eventually become defunct when they produce too little fuel for extraction to be profitable to their operators.
The big question is what to do with these enormous structures when the fossil fuels stop flowing. With curbing climate change rising up the international agenda, and with some questioning whether we have already passed peak oil, hastened by the coronavirus pandemic, the number of defunct rigs in the ocean is set to get bigger. Removing them from the water is incredibly expensive and labour-intensive. Allowing them to rust and fall into disrepair is an environmental risk that could seriously damage marine ecosystems.
For some species, offshore rigs are even better nurseries than natural reefs. The towering pylons are the perfect spawning grounds for tiny fish larvae
But there is one way in which these old rigs can be remarkably useful: the subsurface rig provides the ideal skeleton for coral reefs. Teeming with fish and other wildlife, offshore rigs like Platform Holly are in fact the most bountiful human-made marine habitats in the world.
The practice of transforming rigs into reefs in the United States dates back almost 40 years. In 1984, the US Congress signed the National Fishing Enhancement Act which recognised the benefits artificial reefs provided and encouraged states to draw up plans to turn defunct rigs into reefs. The five coastal states on the Gulf of Mexico – Alabama, Florida, Louisiana, Mississippi and Texas – all have rigs-to-reefs programmes and have converted more than 500 oil and gas platforms into artificial reefs.
When oil companies cease drilling in these states, they decommission their platform by sealing the oil well. Then they can either choose to remove the entire platform or convert it into a reef by removing just the upper section of the structure.