Experts say one-third of the oceans' coral reefs face extinction by the middle of the century if nothing is done to save them.  The reefs are home to a vast array of sea creatures, which experts say would also be endangered by the loss of the reefs.  VOA's Jessica Berman reports.

A group of thirty nine leading coral experts from around the world sounded the alarm in the first-ever global assessment of coral reefs.

Corals are tiny sea creatures that lay their skeletons down to form large reefs that have been built over millions of years.   

Kent Carpenter of Old Dominion University in Virginia led the study, published this week in the journal Science, on the threat to the world's coral reefs, which are produced in tropical and sub-tropical seas in coastal waters.

Carpenter says steps must be taken now to reduce greenhouse gas emissions and stop over-fishing and pollution of the oceans.

"If we do not do those things, then, at the current level of how things are going, we will probably lose our coral reefs by the middle of this century," Carpenter said. "So, 2050 is the date that many people are predicting that coral reefs will cease to exist."

Carpenter says, as ocean temperatures rise, corals throw off algae attached to them that are essential for their survival.

"Normally, when you see a coral, it's tan or green or some colorful color," he said. "But when they expel their algae inside of them, then they become white.  And this is a phenomenon known as bleaching.  Another consequence of higher temperatures is increased disease, and this can cause mass die off."

Carpenter says the coral reefs at greatest risk of extinction are the most common - the branching or staghorn coral.

According to the report, the Caribbean has the greatest number of threatened coral species.  

The report also lists corals within the Pacific's Indo-Malay-Philippine Archipelago as threatened because of large concentrations of people.
Experts say more than 25 percent of marine species depend upon the reefs for their survival.

Carpenter says humans also depend upon coral reefs.

"They are important for food and important for other types of livelihoods," he said. "So, if we lose the ecosystems, we lose not only the biodiversity, but we also lose the capability of people to obtain income and food from coral reefs."

However, Carpenter says he and other marine biologists believe the coral reefs can be rescued through targeted conservation efforts and a reduction in greenhouse gas emissions.  
Earlier this week, a U.S. government report said nearly half of coral reefs in U.S. government territory are in poor or fair condition.