Australia's Great Barrier Reef being threatened by global bleaching event

Australia's great barrier reef is now being threatened by the third global coral bleaching event, the longest the world has ever seen, as the devastation could last well into 2017.

Human-induced climate change has been increasing the frequency of mass coral bleaching events, as areas of the pacific such as Fiji, Kiribati and New Caledonia begin suffering a mass bleaching event from an El Nino re-enforced warm water travelling through the equatorial pacific.

The U.S. National Oceanic and Atmospheric Administration (NOAA) has said the global bleaching event, which began in 2014, could become a two-and-a-half-year event if conditions persist.

"The intensity (on the Great Barrier Reef) hasn't necessarily manifested itself as badly as it might have been forecast... but saying that, the next three to four weeks will be the crunch time as to whether the reef bleaches," manager of the Healthy Oceans Program at the University of Queensland, marine scientist Dr Tyrone Ridgway told the Guardian Australia on Wednesday.

The warm water is now on the world's largest reef system's doorstep, with reports of bleaching occurring on some flats in the Great Barrier Reef as well as round the marine research station on Heron Island towards the southern reach of the system.

Scientists are hoping for bad weather, such as clouds, rain and storms to mix the water and keep temperatures at bay, otherwise the still conditions - ideal for tourists - over the next few weeks will "ramp up the heat."

Coral reefs are one of the most important and productive marine ecosystems that the world depends on for tourism and fishery sustainability.

Coral bleaching occurs when stress such as heat caused the animal to expel the symbiotic algae, loosing vital nutrients and energy reserves, thus color, leading to the wide scale loss of productive habitats for fish.

The coral host then becomes weak and susceptible to disease, and when bleaching is prolonged, the animal can die.

Recent research suggests corals with high levels of fat or other energy reserves can withstand annual bleaching events, which is critical to predicting the persistence of corals and their capacity to recover from more frequent events resulting from climate change.

Severe bleaching events however may take highly impacted coral reefs up to 10 years to recover.