There are thousands of oil and gas platforms in the world’s oceans and in the coming decades many will become obsolete. Some people think that instead of treating them as industrial waste, we should embrace the ecosystems they’ve created and leave them in the sea as artificial reefs. This approach has been adopted by some US states, and scientists are considering whether this could also work in the North Sea.Produced and presented by Celestina OlulodePicture: Getty Images