An international team of scientists and coral reef experts have, in a letter to the Australian Prime Minister Malcolm Turnbull, urged greater action to protect the iconic Great Barrier Reef — a region that is currently witnessing its worst bleaching event on record. The letter, signed by past and present presidents of the International Society for Reef Studies on behalf of over 2,000 attendees of the International Coral Reef Symposium recently held in Honolulu, was sent to Turnbull on Saturday.

“This year has seen the worst mass bleaching in history, threatening many coral reefs around the world including the whole of the northern Great Barrier Reef, the biggest and best-known of all reefs,” the scientists reportedly wrote in the letter. “The damage to this Australian icon has already been devastating. In addition to damage from greenhouse gasses, port dredging and shipping of fossil fuels across the Great Barrier Reef contravene Australia’s responsibilities for stewardship of the reef under the World Heritage Convention.”

Coral reefs, which are delicate marine biodiversity hotspots where corals grow in symbiosis with algae, become bleached when they are stressed due to a rise in ocean temperatures, acidity, or both, which expels the symbiotic algae living in corals’ tissues, causing them to turn completely white.

Over the past two years, corals in the Great Barrier Reef — a fragile biodiversity hotspot that consists of nearly 3,000 individual reefs — have come under increasing stress from climate change-induced ocean warming and the El Niño weather phenomenon.

According to recent surveys, over 90 percent of the 1,400 mile-long Great Barrier Reef has been affected by some level of bleaching, and nearly 35 percent of corals in its northern and central parts have died as a result.

gbr-results-lowres (1) A map of the Great Barrier Reef showing results of aerial surveys of over 900 reefs. Photo: ARC CENTRE OF EXCELLENCE FOR CORAL REEF STUDIES/TOM BRIDGE AND JAMES KERRY

“That’s an absolute catastrophe,” Terry Hughes, director of Australia’s ARC Centre of Excellence for Coral Reef Studies, told the Associated Press. “There’s nowhere to hide from climate change.”

Earlier this month, after fending off accusations of not doing enough to protect the reef, the Australian government announced the creation of a 1 billion Australian dollar ($740 million) fund to protect the reef. The fund will be used to finance clean energy projects across the reef’s catchment area.

However, the problem of coral bleaching is not restricted to the Great Barrier Reef alone. According to the latest assessment by the National Oceanic and Atmospheric Administration’s (NOAA) Coral Reef Watch, bleaching events, triggered primarily by warm ocean waters — an event that has been exacerbated by the recent strong El Niño event — have been reported in corals near at least 38 countries and Island groups, with some regions in the central Pacific reporting even higher mortality than the Great Barrier Reef.

“U.S. coral reefs, in particular, were hit quite hard by this event; predictions indicate that as of the end of 2015, almost 95 percent of U.S. coral reefs were exposed to the prolonged high temperatures that cause coral bleaching,” the NOAA said. “By April 2016, all U.S. coral reefs had been exposed to bleaching thermal stress.”