Widespread Coral Bleaching Strikes Great Barrier Reef Again in 2017

During early 2017, the region over Australia’s Great Barrier Reef (GBR) experienced its hottest summer atmospheric temperatures on record. Peak water temperatures lag peak air temperatures by about a month. But already, sections of one of the world’s most vital marine sanctuaries are experiencing bleaching and disease. Worryingly, bleaching and heat stress is expanding over the reef at a faster rate than at the same time last year.

Coral Bleaching Great Barrier Reef

(The Great Barrier Reef is already experiencing extensive bleaching in 2017. With warmer waters headed toward the reef over the coming weeks, researchers fear that this year’s coral mortality event could match or exceed 2016’s severe damage and loss. Image source: Commons.)

A Precious Global Treasure Under Threat

During 2016, the GBR experienced its worst coral bleaching event on record. This severe event followed two years (2014-2015) in which the reef saw less widespread bleaching. A strong El Nino combined with the highest global temperatures ever measured to produce ocean conditions that were too hot to support living corals and many regions saw bleaching and high mortality. In the reef’s northern sections, more than 2/3 of the corals bleached and died out.

Scientists who’d long warned that global warming would put the fate of the great reef at risk, issued an alarm and a call for action. Global temperatures had now reached a threshold that threatened to put Australia’s natural wonder at risk with far greater frequency than ever before. Scientists warned that by the 2030s, ocean temperatures would be warm enough to produce a bleaching event similar to the 2016 die-off every 2-3 years. A separate study indicated that the reef could experience severe coral bleaching through at least 2040 (and well beyond if the world continued to burn fossil fuels and to warm up at such rapid rates).


(Under human-forced warming the frequency of coral bleaching events and reef mortality is expected to dramatically increase over the coming decades. However, with global temperatures now 1.2 C warmer than 1880s levels, the amount of stress to corals is already remarkably high. Image source: The World Resources Institute.)

Some questioned if the reef could survive such a severe onslaught of global heat brought about by human fossil fuel emissions. Others pointing out that, unless those heat-trapping emissions were dramatically curbed, warming alone had the potential to kill off most of the reef within the next 20 years.

More Coral Bleaching as Ocean Near GBR Fails to Cool in 2017

Nearer-term concerns were also raised that risks to the reef remained high in the present abnormally warm ocean environment. For as 2017 followed 2016, the global coral bleaching event that began in 2014, and that had already claimed the lives of so many of the world’s corals, remained in force.

During the winter of 2016-2017, a weak La Nina event (NOAA) brought some hope that the GBR might get a chance to recover from this most recent spate of extreme ocean warmth. However, by February, La Nina (which was never strong enough to be officially recorded by Australia’s BoM) had faded even as indicators pointed toward a new El Nino beginning to gather. Meanwhile, global atmospheric carbon continued to increase — hitting 490 CO2e by late 2016.


(NOAA predicts another bad year for the world’s corals as a new El Nino threatens to emerge and as global temperatures remain near record highs set in 2016. Image source: NOAA.)

Ocean temperatures in the 30 C + range that typically produce bleaching began to spread over parts of the reef. These conditions were warmer than during the same period of 2016 — raising the awful potential that impacts to the reef during 2017 could be as bad or even worse than last year’s record event.

Worse than 2016 So Far

As of this week, new reports of bleaching were starting to emerge in six GBR reefs in the region of Mission Beach. According to Queensland’s Environment Minister Steve Miles:

“Queensland has just experienced its hottest summer on record and above average temperatures are predicted until the end of March. Some corals were still under stress from last year’s bleaching event and that was exacerbated by a warmer than average winter. The next four weeks will be critical and we can only hope that water temperatures will be cooler than the forecast.’’

The six reefs in question, stretching from Cairns to Townsville, already showed 60 percent bleaching — primarily among the more heat-sensitive corals. And the extent of bleaching was more advanced than during the same time in 2016. Over the coming weeks, the pulse of warm water is expected to spread, putting still more corals at risk as the unprecedented ocean heat moves southward through the marine sanctuary.

So it appears that the GBR is in for another rough summer — one with the potential to see impacts similar to or exceeding those of 2016. Moreover, with global oceans continuing to warm, with world governments still dragging heels on carbon emissions reductions, and with Trump and others vowing to reinvigorate coal, the plight of the GBR is now quite dire.



Great Barrier Reef Faces New Coral Bleaching Threat

Ecologists Steel For More Coral Bleaching on Great Barrier Reef

Large Scale Projections of Coral Reef Futures

Reef Authority Reveals More Coral Bleaching

Global Coral Bleaching Event

The World Resources Institute


Hat tip to Keith

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