Australia's Great Barrier Reef susceptible to more bleaching: UN study

Australia's Great Barrier Reef will bleach more regularly as human induced climate change increases the frequency of mass coral bleaching events.

The World Heritage listed Great Barrier Reef suffered its worst mass bleaching event in early 2016 as El Nino-re-enforced warm water lifted sea surface temperatures some 0.73 degrees Celcius warmer than the 1961-1990 average, their warmest on Australia's weather bureau record. Some 90 percent of the GBR suffered bleaching, killing 20 percent of corals.

"The El Nino, in combination with background global warming, led to record-warm sea surface temperatures around much of Australia during the first half of the year, including in the Coral Sea and to Australia's northwest, where widespread coral bleaching was observed," Australia's Bureau of Meteorology said in its annual climate report on Thursday.

"The bleaching event in the northern part of the Great Barrier Reef was the worst on record, affecting some 1000 km of reef north of Lizard Island, while in Western Australia it was the third time a bleaching event has ever been recorded."

It's likely to be an annual event within the next half century however, a United Nations Environment Programme (UNEP) and University of Miami study projecting the future of coral reefs under climate change, published Thursday, shows. Reefs around Taiwan and the Bahamas will be the first to suffer the annual bleaching by 2043, with Bahrain, Chile and reefs in the Pacific to follow about a decade later.

Should the Paris Climate Summit's aspirational pledge to limit global temperatures rises by two degrees Celsius be met, it would buy Australia areas of the Pacific and other low and high latitude reefs approximately 25 more years for conservation efforts, the study shows.

"It is imperative that we take these predictions seriously and that, at the very minimum, we meet the targets of the Paris Agreement," UNEP chief Erik Solheim said in a statement.

"Doing so will buy time for coral reefs and allow us to plan for the future and adapt to the present."

Coral reefs are one of the most important and productive marine ecosystems that the world depends on for tourism and fisheries sustainability, generating an estimated 375 billion U.S. dollars for the global economy annually.

Coral bleaching occurs when stress such as heat caused the animal to expel the symbiotic algae, loosing vital nutrients and energy reserves, thus color, leading to the wide scale loss of productive habitats for fish.

The coral host then becomes weak and susceptible to disease. When bleaching is prolonged, the animal can die.

A single reef however needs on average five years to recover from just one bleaching event, thus annual bleaching will invariably cause major changes to the ecological function of one of the world's most precious resources, study leader Dr Ruben van Hooidonk of NOAA and the University of Miami said.

"Further, annual bleaching will greatly reduce the capacity of coral reefs to provide goods and services, such as fisheries and coastal protection, to human communities," van Hooidonk said. Endit