Cairns, Australia (CNN) A coral fertility treatment designed to help heal damaged parts of Australia's Great Barrier Reef is showing signs of success and now needs to be scaled up to create a bigger impact, the lead scientist tells CNN.

Peter Harrison, a professor at Southern Cross University in Australia, said he is "excited by the results" which show the experimental process known as "coral IVF" is working on a small scale.

Recently returned from a trip to the reef, Harrison said his team managed to "significantly increase" the numbers of baby coral on reefs at Heron Island and One Tree Island, where they laid millions of coral larvae 18 months ago.

"There's a very clear outcome, the higher the numbers of larvae that you put into the reef system, the more coral recruits you get," Harrison said. "The pilot studies at small scales are giving us hope that we will be able to scale this up to much larger reef scales."

The 2,300km-long (1,500 miles) Great Barrier Reef -- a UNESCO World Heritage Site -- lost around half of its coral in the past few years after two mass bleaching events in 2016 and 2017 , a pattern repeated on coral reefs around the world.

Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching There are 'winners' and 'losers' among corals as they respond to the accumulating impacts of climate change. Hide Caption 1 of 14 Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching There are variations in the appearance of severely bleached corals. Here, the coral displays pink fluorescing tissue signalling heat stress. Hide Caption 2 of 14 Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching The different color morphs of Acropora millepora, each exhibiting a bleaching response during mass coral bleaching event. Hide Caption 3 of 14 Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching A bleached Acropora colony. Hide Caption 4 of 14 Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching A severely bleached branching coral amongst the minimally bleached boulder coral. Hide Caption 5 of 14 Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching Dramatic coral bleaching, seen in Australia's Great Barrier Reef from March 2016. Hide Caption 6 of 14 Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching Some of the bleaching of reefs in the northern section has been described as "extreme." Hide Caption 7 of 14 Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching Bleaching occurs when the marine algae that live inside corals die. Of the reefs surveyed in the northern third of the Great Barrier Reef, 81% are characterized as "severely bleached." Hide Caption 8 of 14 Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching "At some reefs, the final death toll is likely to exceed 90%," Andrew Baird, of the ARC Center of Excellence for Coral Reef Studies, says. Hide Caption 9 of 14 Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching A photo taken on September 22, 2014, shows bleached coral on the Reef, a key Australian tourist attraction. Hide Caption 10 of 14 Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching Tourism on the Great Barrier Reef generates an annual income of A$5 billion ($3.9 billion) and employs nearly 70,000 people. Hide Caption 11 of 14 Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching Of the reefs surveyed in the northern third of the Reef, 81% are characterized as "severely bleached." Hide Caption 12 of 14 Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching Driven by ocean temperatures that have been 1-2 degrees Celsius (1.8-3.6° F) above average, the bleaching event has left large sections of coral drained of all color and fighting for survival. Hide Caption 13 of 14 Photos: Australia's Great Barrier Reef suffers 'extreme' coral bleaching The Reef has suffered two mass bleaching events, in 1998 and 2002, but the extent of the bleaching in these years was less severe than in 2016. Hide Caption 14 of 14

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