More than 90 percent of the Great Barrier Reef coral that was surveyed this year was bleached.  Australian government scientists stated that this is such a mass event in seven years in the world’s largest coral reef ecosystem.

Bleaching is often caused by global warming, but this is the reef’s first bleaching event during a La Niña weather pattern, which is associated with cooler Pacific Ocean temperatures. The Great Barrier Reef Marine Authorities said in an annual report released late Tuesday that found that 91 percent of the areas surveyed were affected. Coral bleaches as a heat stress response and scientists are hoping that most of the coral will recover from this situation, said David Wachenfeld, chief scientist at the authority, which manages the reef ecosystem.

Last December, the first month of the Southern Hemisphere summer, was the hottest December the reef had experienced since 1900. A “marine heatwave” had set in by late February. A United Nations delegation visited the reef in March to assess whether the reef’s World Heritage listing should be downgraded due to the ravages of climate change.

In July last year, Australia gained enough international support to defer an attempt by UNESCO, the United Nations’ cultural organization, to downgrade the reef’s World Heritage status to “in danger” because of damage caused by climate change. But the question will be back on the World Heritage Committee’s agenda at its annual meeting next month