With an estimated 30% of all reefs already severely damaged, the authors write, and close to 60% liable to be lost by 2030, there are no pristine reefs left.
They say the link between coral bleaching and increased climate change, "considered dubious by many reef researchers only 10 to 20 years ago, is now incontrovertible".
Yet the bleaching - which happens when corals stressed by overheating expel the tiny organisms that provide their colour - is "conspicuously patchy".
Bleached and unbleached corals are often found side by side, and the same species seem to develop different tolerances in different parts of their range. Another factor is the very high level of genetic diversity in corals.
So some reefs will prove more resilient than others to the emergent threats they face, the authors believe, with many changing rather than disappearing entirely.
But they write: "We can be certain nonetheless that the projected increases in carbon dioxide and temperature over the next 50 years will substantially and very rapidly exceed the conditions under which coral reefs have flourished over the past half-million years."
They argue for many more marine reserves, or no-take areas( NTAs), to protect reefs against overfishing, which can alter the entire dynamics of a reef.
Alex Kirby BBC NEWS | Science/Nature 14 August, 2003
