Back on 17 March, 2017 Joshua Robertson’s article in the Guardian Stopping global warming is only way to save Great Barrier Reef, scientists warn reported four things happening simultaneously. First, a paper by 46 scientists published in Nature showed that bleaching of the Great Barrier Reef in 1998, 2002 and 2016 was determined by ocean surface temperature; water quality had nothing to do with it.
Secondly, Terry Hughes, the lead author of the paper was embarking on aerial surveys to chart the effects of the latest 2017 bleaching event, the first in consecutive years, and the first in a non-El Niño year.
Third, Queensland government officials were in Paris meeting with UNESCO officials to appeal for more time to make good on conservation efforts to ward off an “in-danger” listing for the reef. This conservation plan does not mention global warming, concentrating on such things as water quality.
Fourth, Queensland premier Annastacia Palaszczuk went to India to lobby Adani to proceed with its giant coal mine in the Galilee Basin.
In other words, global warming is the main danger to the reef, being manifest at current levels, while politicians chase water quality and direct their efforts to making global warming worse through producing more coal.
The Hughes research paper found that 91% of coral on the reef had suffered from bleaching over the past two decades. In 2016, 22% of the Reef was killed off in one hit.
- preserving more than 10 per cent of coral reefs worldwide would require limiting warming to below +1.5°C (atmosphere–ocean general circulation models (AOGCMs) range: 1.3–1.8°C) relative to pre-industrial levels.
Then in December last year a new report led by researchers at the National Oceanic and Atmospheric Administration (NOAA) found that if current trends continue, by 2050 more than 98% of reefs world-wide are expected to be exposed to bleaching-level thermal stress in each year. Reefs need 10-15 stress-free years to recover, if they are going to at all, and proximity to other healthy reefs is important.
Some reefs in the world appear to have gone forever. As Jules Howard reports:
- Of 21 reefs monitored by scientists in the Seychelles, for instance, 12 have since recovered after a coral bleaching episode in 1998. (The other nine? Now seaweed-covered ruins.)
There is more on coral reef resilience in this post last year, but in general terms it takes years for any regrowth to show, and frequent bleaching will be terminal. Then there is acidification.
The Hughes et al paper shows the footprint of the 1998, 2002 and 2016 events, with red representing greater than 60% bleached:
This article shows the 2017 bleaching compared to 2016:
This image from a recently published Climate Council report Climate Change: A Deadly Threat To Coral Reefs shows the coral death rate after the 2016 bleaching:
In the Far Northern and Northern sectors there is virtually no runoff from farms and other activity on land. Coral damage reflects ocean water temperature.
Just to remind you, from the post Great Barrier Reef will never be the same, here’s what bleaching does:
This is what a really healthy reef looks like:
This is a before and after showing dead coral:
The Climate Council report tells us that the great Barrier reef supports the livelihoods of 69,000 Australians and is worth $7 billion annually to the economy. Globally, the economic figure is $1 trillion and the livelihoods supported number 500 million.
For dangerous climate change we do not have to wait for warming to reach 2°C or 1.5°C. It’s happening now.
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