Coral bleaching or loss of algae poses a great threat to the Great Barrier Reef's survival. Last year, bleaching due to extremely warm ocean temperature caused two-third of the corals to die in major parts of the northern sector of the reef. That was the third and worst sever bleaching.

Scientists published a new study in the journal Nature that said climate change is the single greatest threat. They said another bleaching event might occur this year. Study co-author Morgan Pratchett, from Queensland's James Cook University said that the solution lies on what the government around the world on what they would do in terms of mitigating further rise in temperatures.

Coral bleaching is caused by rising water temperatures which is exacerbated by man-made climate change. The ocean absorbs about 93 percent of the Earth's increasing heat. Bleaching happens when corals pushes out the algae, zooxanthellae, when they are stressed from extremely warm temperatures.

If water conditions return to normal, the corals can recover. However, it may take decades and if the stress continues and the hotter the water, the corals can die.

BBC reported that improving fishing practices or water quality would not be enough according to Prof Pratchett. The reef was given World Heritage status in 1981.

The UN said it's the most biodiverse, of enormous scientific and intrinsic importance of all the World Heritage sites. The Great Barrier Reef is much like the major US reef that is located off the Florida Keys. It is carefully protected by government and individuals who try to preserve the quality of water in the area according to The Washington Post.

No matter how hard individuals defend the corals from tourists and fishing activities, ever-warmer ocean temperatures will override any local attempts to make the reefs resilient. The world has lost roughly half of its coral reefs in the last 30 years and scientists now struggle to prevent wipeout to protect the remaining reefs for the next decades.

Even if the world could stop global warming now, scientists expect more than 90 percent of corals will die by 2050.