Aerial surveys showed that "some southern areas of the Reef that had little or no bleaching in 2016 and 2017 have now experienced moderate or severe bleaching," the authority said.
Warmer temperatures, particularly in February, led to the latest bleaching, the GBRMPA said. Bleaching does not automatically mean the corals will die. Mildly or moderately affected reefs usually recover.
Saving the Great Barrier Reef
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Key tourism reefs in northern and central areas should survive, the authorities said.
Ocean warming in 2016 and 2017 killed almost half the coral.
What happens when coral gets stressed? Global warming and environmental changes can cause corals to lose their color, and hinder their ability to feed and reproduce. Scientists and policy makers are sounding alarm bells.
Image: imago/OceanPhoto
Trouble in paradise
Some 2,500 scientists, policymakers and managers came together in Honolulu in June 2016 for the world's largest summit dedicated to the future of coral reefs. With coral reefs threatened by global warming, participants at the 13th International Coral Reef Symposium are calling for a joint rescue effort.
Image: picture alliance/WILDLIFE
World is watching
The event gathered guests from 97 countries, including the presidents of Palau, Micronesia, and the Marshall Islands. Coral reefs are a key source of income in those countries, mostly through tourism.
Image: picture alliance/WILDLIFE
Too warm for comfort
The Pacific nations are worried about the future of their tourist hotspots, as coral reefs face so-called "bleaching" due to rising sea temperatures. "If our coral reefs are further degraded, then our reef-dependent communities will suffer and be displaced," leaders of Palau, Micronesia, and the Marshall Islands said in an open letter.
Image: imago/OceanPhoto
Corals in crisis
Bleaching happens when coral is stressed by hot ocean waters or other changes in the environment. In response, corals may release tiny symbiotic algae which drains them of color. More importantly, bleaching affects their ability to feed and reproduce.
Image: Imago
Pale as death
Severe or prolonged bleaching might kill off corals entirely. Scientists have detected bleached coral in the past two years in oceans around the world. They expect the process to continue thought 2016.
Image: imago/blickwinkel
Giant from Down Under
The 2,300-kilometer-long (1,429-mile-long) Great Barrier Reef is the world's largest coral reef system and its largest living structure. It is also among Australia's main tourist attractions, generating around $3.9 billion (3.5 billion euros) annually.
Image: Imago/ZUMA Press
Tough times for the Great Barrier Reef
Almost one-half of the coral in the reef's northern third have died in the past three months [in 2016], according to James Cook University professor Terry Hughes. The most affected area is remote and unpolluted, with very little fishing and no coastal development. "That's an absolute catastrophe," Hughes said. "There's nowhere to hide from climate change."
Image: Dorothea Bender-Champ for ARC Centre of Excellence for Coral Reef Studies
Fighting for hope
Despite the bad news, scientists claim the problems can be managed with proper funding and political backing. "We are not ready to write the obituary for coral reefs," Professor Hughes said. The scientific community at the conference pledged to work with leaders across the world in order to "curb the continued loss of coral reefs."
