Temperature rise threatens 97% of coral

The risk of a mass coral bleaching in the Great Barrier Reef is low for the time being, but climate change remains a great concern to scientists.

An increase in global temperatures by as little as three degrees Celsius could kill up to 97 per cent of coral in the reef, a Senate estimates committee heard on Tuesday.

"That's dramatic and destructive impact," said Great Barrier Reef Marine Park Authority spokesman Russell Reichelt.

On a positive note, he said the risk of a mass bleaching event, which has happened twice in the past decade, was presently low.

However, there were some early signs of bleaching, with the southern end of the reef warming slightly more than the northern end.

Dr Reichelt warned coral took eight to 15 years to regenerate after a bleaching event and a second bleaching meant coral would never recover.