Industrial civilisation is close to breaching a seventh planetary boundary, and may already have crossed it, according to scientists who have compiled the latest report on the state of the world’s life-support systems. They say ocean acidification is close to critical threshold, posing a threat to marine ecosystems and global liveability. Ian Sample speaks to Prof Helen Findlay, a biological oceanographer at the Plymouth Marine Laboratory, to find out why the oceans have reached this state, and whether there is anything we can do to reverse the damage.