93% of the Great Barrier Reef has been damaged by coral bleaching

Just 7% of the Great Barrier Reef has avoided coral bleaching caused by climate change, scientists have revealed.

Extensive aerial and underwater studies found 93% of the Reef had coral damage ranging from very severe to little. It varied dramatically from north to south along the 1,430 miles (2,300 km) of the Reef off the coast of Queensland, eastern Australia.

Coral bleaching is when the coral is left white and vulnerable after the symbiotic algae living in their protective tissues is expelled by changes to temperature, light or nutrients.

Professor Terry Hughes, convenor of the National Coral Bleaching Taskforce that is documenting and studying the event, said: “We’ve never seen anything like this scale of bleaching before. In the northern Great Barrier Reef, it’s like 10 cyclones have come ashore all at once. Towards the southern end, most of the reefs have minor to moderate bleaching and should soon recover.”

Researchers flew over 911 individual reefs to map out the extent and severity of bleaching and found just 68 reefs (7%) escaped bleaching entirely. More moderate bleaching was found on the Reef between Cairns and Mackay.

On the northern reef, in the region north of Port Douglas all the way up to the northern Torres Strait between Australia and Papua New Guinea, bleaching was the most extreme. They found between 60% and 100% of corals were severely bleached on 316 reefs.
Professor Andrew Baird from the ARC Centre of Excellence for Coral Reef Studies, said: “Tragically, this is the most remote part of the Reef, and its remoteness has protected it from most human pressures: but not climate change. North of Port Douglas, we’re already measuring an average of close to 50% mortality of bleached corals. At some reefs, the final death toll is likely to exceed 90%. When bleaching is this severe it affects almost all coral species, including old, slow-growing corals that once lost will take decades or longer to return.”

Daniel Gschwind, chief executive of the Queensland Tourism Industry Council, added: “Thankfully, many parts of the reef are still in excellent shape, but we can’t just ignore coral bleaching and hope for a swift recovery. Short-term development policies have to be weighed up against long-term environmental damage, including impacts on the reef from climate change.”