What if all coral reefs die ? Experts are scared.

Coral reefs are dying, and scientists are wondering what will happen if they disappear.

Coral reefs are part of the foundation of the ocean food chain. Nearly half the fish the world eats make their home around them.

"Whole nations will be threatened in terms of their existence," said Carl Gustaf Lundin of the International Union for the Conservation of Nature.

Coral reefs are in danger because of global warming, pollution, coastal development, and also by the damaged done by bottom-dragging fishing boats. The souvenir and jewelry businesses are also adding to losses of the coral reefs. 

At least 19 percent of the world's coral reef are already gone, including about 50 percent of those in the Caribbean. An additional 15 percent could be dead within 20 years, according to the National Oceanic and Atmospheric Administration (NOAA). Old Dominion professor Kent Carpenter, warned that if global warming continues unchecked, all corals could be extinct within 100 years.

"You could argue that a complete collapse of the marine ecosystem would be one of the consequences of losing corals," Carpenter said. "You're going to have a tremendous cascade effect for all life in the oceans."

If reefs were to disappear, commonly consumed species of grouper and snapper would not be available. Oysters, clams and other such creatures would also disappear.

"Fish will become a luxury good," said Cassandra deYoung of the UN Food and Agriculture Organization. "You already have a billion people who are facing hunger, and this is just going to aggravate the situation," she added. "We will not be able to maintain food security around the world."

"A world without coral reef is unimaginable," said Jane Lubchenco, a marine biologist who heads NOAA. " Reefs are precious sources of food, medicine and livelihoods for hundreds of thousands around the world. They are also special places of renewal and recreation for thousands more. Their exotic beauty and diverse bounty are global treasures."

Source: Brian Skoloff,  & Seth Borenstein, Associated Press Writers