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The world's coral reefs are increasingly being threatened, mostly because of human activities. 

A group of environmental organizations released a report on the issue in February. The "Reefs at Risk Revisited" report used new information and improved satellite mapping systems to study the world's coral reefs. For the first time, it also considered the effect of climate change on these threatened sea organisms. 

Jane Lubchenco is administrator of the National Oceanic and Atmospheric Administration, or NOAA. She says the problem is serious.

JANE LUBCHENCO: "Approximately 75 percent of the world's coral reefs are currently threatened by a combination of local and global pressures."

Lubchenco says the threat to coral reefs will continue to increase unless something is done to save them. 

JANE LUBCHENCO: "If the current trend persists, the projections in this report tell us that 20 years from now, roughly half the reefs globally will experience thermal stress sufficient to induce severe bleaching in most years. Within the next 50 years this percentage is expected to grow more than 95 percent." 

Nancy Knowlton is with the Smithsonian Institution. She says the threat to coral reefs could have a major effect on sea life.

NANCY KNOWLTON: "It's been estimated that about one - at least one quarter, maybe as much as one third, of all species that live in the ocean live associated with coral reefs. So perhaps it is not too surprising that even more recently an analysis was done that suggests that one third of all coral species are actually at risk of extinction. This makes corals the most endangered animal on the planet, even more endangered than frogs." 

Millions of species of sea life depend on coral reefs for their survival. This makes them an important source of food for millions of people around the world. 

Coral reefs also protect coastlines from storms and flooding. And, they provide economic security for many countries. 

LAURETTA BURKE: "Tourism is an important economic contributor in over 95 countries and territories around the world. It contributes over 20 percent of GDP in over 20 countries."

Lauretta Burke is with the World Resources Institute. She was one of the lead writers of the report. She says more than 275-million people are dependent on the resources from coral reefs, mostly in Southeast Asia and the Indian Ocean.

The report noted overfishing and climate change as two of the most serious threats to the world's oceans. It said higher acidity levels caused by carbon dioxide emissions are also a problem. Other threats include the use of explosives for fishing, as well as the run-off of toxic materials and other pollution.

LAURETTA BURKE: "Overfishing is the most widespread threat affecting about 55 percent of the world's reefs. The threat is particularly high in Southeast Asia. Watershed based pollution and coastal development affect roughly a quarter of the world's reefs." 

Burke says while the reefs around Australia are the best preserved, those in Southeast Asia are the most threatened. Ninety percent of them are at risk, largely because of overfishing.

The report says coral reefs are critically important. It says better management practices and policies must be established to reduce the threats to these valuable ecosystems. I'm Christopher Cruise.