The BBC on the urgent plight of the corals:
The prospects of saving the world's coral reefs now appear so bleak that plans are being made to freeze samples to preserve them for the future.
A meeting in Denmark took evidence from researchers that most coral reefs will not survive even if tough regulations on greenhouse gases are put in place.
Scientists proposed storing samples of coral species in liquid nitrogen.
That way, the corals could be reintroduced to the ocean in the future.