22 September 2010, 15:25 BST
In 1998, 16% of the world's shallow-water reefs died, as a result of global temperatures that were the hottest ever recorded.
Scientists say the die-off could be even worse this year, as coral from Texas to Thailand are bleaching--a stress reaction that indicates survival mode for coral, which are especially vulnerable to warming oceans.
Scientists say this is only the second known global bleaching of coral reefs (following 2008). They hope it won't be as bad, as 2008, but in some areas it is almost certain to be worse.
For instance, last month scientists with the Wildlife Conservation Society reported on what they say is one of the most rapid and severe coral mortality events ever recorded, unfolding in Indonesia.
Source: Sustainable Business
Photo provided by yvonnedierich