A large white coral reef containing important species and fossil traces has been discovered at a depth of more than 500 metres in the Gulf of Naples, in a rare discovery for the Mediterranean. But a new report suggests reefs like this might already be in danger, with global warming crossing dangerous thresholds sooner than expected and the world's coral reefs now in an almost irreversible die-off. It marks what scientists are describing as the first tipping point in climate-driven ecosystem collapse.