Half of the Australia's Great Barier Reef Northern Coral Dead or Dying

Australian scientists said on Wednesday that just seven percent of the Great Barrier Reef, has been untouched by mass bleaching that is likely to destroy half of the northern coral. Bleaching occurs when the water is too warm, forcing coral to expel living algae and causing it to calcify and turn white. Mildly bleached coral can recover if the temperature drops, otherwise it may die.

 Although the impact has been exacerbated by one of the strongest El Nino weather systems in nearly 20 years, scientists believe climate change is the underlying cause.

The Great Barrier Reef stretches 2300km along Australia's North-East coast and is the world's largest living ecosystem. 

UNESCO's World Heritage Committee last May stopped short of placing the Great Barrier Reef on an in Danger list, but the ruling raised long-tern concerns about its future.