CANBERRA, Australia (AP) — An Australian government agency says the Great Barrier Reef is suffering widespread and severe coral bleaching due to high ocean temperatures two years after a mass bleaching event.

The report by the Great Barrier Reef Marine Authority on Friday comes three days before a United Nations delegation is due to assess whether the reef's World Heritage listing should be downgraded due to the ravages of climate change.

The authority manages the world's largest coral reef ecosystem.

The reef has suffered significantly from coral bleaching caused by unusually warm ocean temperatures in 2016, 2017, and 2020.

The previous bleaching damaged two-thirds of the coral.

The agency said about 3,000 reefs make up the Great Barrier Reef.

According to the agency, the reefs that were the most heavily damaged are located in the Townsville region.

During the 2019-20 summer, the agency said scientists surveyed 1,036 reefs by plane and found that 40% had no or negligible bleaching, 35% had moderate bleaching and 25% had severe bleaching.