The majority of the world's coral reefs may be killed off by rising levels of greenhouse gases, according to a team of UN and World Bank scientists.
They have warned that Australia's Great Barrier Reef will be one of the first victims.
The scientists also added another warning about the great coral reefs in the Caribbean, which they claim will disappear within the lifetime of people alive today.
Carbon dioxide levels, they claim, have risen so much that they are making it impossible for coral to live and reefs will be reduced to seaweed beds, rubble and only scattered coral will remain.
Fish and other marine life which shelter in the reefs would be lost and coastal areas to which they give some protection would also suffer rising sea levels.
Most significant in this report is that the ability of the oceans to absorb carbon dioxide from human activity may also be reaching limits.