A Marine scientist also claimed on Monday reefs badly damaged by global warming may not be able to recover.
Warmer oceans triggered the death of between 50 and 98% of coral reefs in a region stretching from northern Mozambique to Eritrea to Indonesia in 1998 and although there has been some recovery, concern remains.
Dr Carl Lundin, head of the marine programme of the Swiss-based World Conservation Union, said if climate changes continue - due to carbon dioxide emissions - temperatures in the oceans will go up.
"So virtually all the coralline islands have a decent chance of disappearing in 50 years."
Coral reefs are among the most diverse and productive communities on earth.
Found in warm, clear, shallow waters of tropical oceans worldwide, reefs have functions ranging from providing food and shelter to fish and invertebrates to protecting the shore from erosion.
Many coral reef organisms can only tolerate a narrow range of environmental conditions and are very sensitive to damage from environmental changes such as rising temperatures, which can cause bleaching and eventual death.
Lundin said sustained warming up of ocean currents which followed the El Nino effect in 1998 resulted in bleaching and widespread damage to corals in the Indian Ocean.
"So a very large region has been affected and an awful lot of damage has been caused by the temperature increases which varied from one to two to generally up to five degrees Celsius."