It is one of the seven natural wonders of the world, with billions of creatures living in harmony among over a thousand miles of colourful coral.

But Australia's Great Barrier Reef is in danger of being wiped out by climate change and widespread coral bleaching.

Scientists have now suggested that all is not lost for the World Heritage site, as a small portion of its reefs may be resilient enough to keep much of the rest alive.

About three per cent of the site's 3,800 coral reefs have so far emerged unscathed from a host of threats, from warming waters to pollution, bleaching and disease.

If protected, these cool-water reefs could supply larvae to nearly half of the entire ecosystem in a single year, report scientists from the University of Queensland.

'Finding these 100 reefs is a little like revealing the cardiovascular system of the Great Barrier Reef,' said the study's lead author Professor Peter Mumby.

Unlike many other parts of the reef, these 100 are not being eaten up by crown-of-thorns starfish predators.

They are also located in areas that enable them to send coral larvae along ocean currents, reaching a large number of other reefs.

'The presence of these well-connected reefs on the Great Barrier Reef means that the whole system of coral reefs possesses a level of resilience that may help it bounce back from disturbances,' said study coauthor Karlo Hock.