It is only really in the past decade that science has begun to tell us that the man-made changes now occurring in the oceans – from acidification to overfishing to the growth of dead zones – represent some of the greatest threats to life on Earth. There has been a need for a book that sets our current predicament in the context of previous changes in ocean chemistry and periods of extinctions. I was once nearly persuaded to write one. I’m glad I didn’t, for Callum Roberts has clearly done a better job than I would have.

Roberts is that rare thing, a practising scientist who can write clearly and fluently, and use a well-researched example to explain something you had previously only dimly understood. To be able to unravel so many complexities is impressive. When they need explaining so urgently it is, frankly, a triumph. His