In the latest update on the condition of Australia's Great Barrier Reef (GBR), the largest die-off of corals ever recorded there has been confirmed.
The worst affected area is a 700km stretch of reefs in the GBR's northern region, which lost an average of 67% of its shallow-water corals in the past eight to nine months. Further south, over the central and southern regions, the mortality was lower.
“Most of the losses in 2016 have occurred in the northern, most-pristine part of the Great Barrier Reef. This region escaped with minor damage in two earlier bleaching events in 1998 and 2002, but this time around it has been badly affected,” said Professor Terry Hughes, Director of the Australian Research Council (ARC) Centre of Excellence for Coral Reef Studies based at James Cook University. He had conducted extensive aerial surveys at the height of the bleaching.
Professor Andrew Baird, also from the ARC Centre, added, “The good news is the southern two-thirds of the Reef has escaped with minor damage. On average, 6% of bleached corals died in the central region in 2016, and only 1% in the south. The corals have now regained their vibrant colour, and these reefs are in good condition.” In October and November, he had led teams of divers to re-survey the reefs in October and November.
“The patchiness of the bleaching means that we can still provide our customers with a world-class coral reef experience by taking them to reefs that are still in top condition,” said Craig Stephen, who manages one of the GBR’s liveaboard tourist operations. Tourism on the GBR employs 70,000 people, and generates $5 billion in income each year.
In addition, in the northern offshore corner of the Great Barrier Reef Marine Park, along the eastern edge of the continental shelf, there is a large corridor of reefs that had not suffered much damage. "We suspect these reefs are partially protected from heat stress by upwelling of cooler water from the Coral Sea," said Professor Hughes.
Although scientists expect the northern region to regain the lost corals in 10 to 15 years' time, they are concerned that if a fourth bleaching event took place, the recovery process would be disrupted.