Another Greenie shriek about the Great Barrier Reef

This piece of research must have been frustrating to its authors.  They found that the presumed evil -- farm runoff -- actually HELPED the barrier reef.  So they had to do a lot of scratching to turn that around.

The big drama about the reef is that it undergoes periodic bleaching  --  when the coral expels its symbiotic algae.  Nobody likes the look of that but the corals mostly recover after a while.  So that is what all good men and true rally to prevent.  STOP the bleaching!  And now we have found something that prevents it to a degree:  Farm runoff!  How big a disappointment can you get? Farm runoff was supposed to KILL the reef!

But by scratching around in their data, the authors found something to warm their pessimistic hearts.  They found that once the coral had been harmed by some "disturbance", farm runoff hindered recovery to some degree.  But if coral amid farm runoff is less damaged in the first place, does that not make the recovery rate of less concern?

Not so fast!  The authors say.  You have got to balance one effect against another to get an overall conclusion and we have got this nifty little model that will do just that!  So we run the model and we find that that a "6–17% improvement in water quality will be necessary to bring recovery rates in line with projected increases in coral bleaching".

So there's the African-American in the woodpile!  It is all based on a "projection", or in layman's terms, a guess. And the projection is heroic.  They ASSUME that global warming will steadily increase and they ASSUME that warming is the main cause of coral bleaching.  There are large scientific arguments against both those assumptions so if we take them away what is left?  Two people can play the projection game so I project that farm runoff is on balance neither helpful nor harmful so that Nothing needs to be done. Nothing!  Horrors!

My comments so far spring just from a reading of the abstract.  I shudder to think what I would find if I studied the whole article.  I taught applied statistics at a major Australian university for a number of years so I know the tricks researchers get up to if their results don't suit them.  There were so many collaborators on this article that something HAD to come out of it.  Re-running their model with more cautious assumptions would be a ball of fun.

I follow the press release below with the journal abstract


Scientific research published today on the impacts of poor water quality on some Great Barrier Reef corals shows why it’s vital the Queensland Government passes new rules on farm pollution, the Australian Marine Conservation Society (AMCS) says.

The study, published in the journal Nature Ecology and Evolution, found corals in the central and southern sections of the reef would need improvements in water quality of between six and 17 per cent to keep their recovery rates in line with projected increases in coral bleaching.

Corals exposed to poor water quality were also more susceptible to disease and outbreaks of Crown of Thorns starfish, the study found.

Proposed Queensland government laws would phase out harmful farming practices that cause pollution and sediment to run into rivers and out into the reef.

Dr Lissa Schindler, AMCS Great Barrier Reef campaign manager, said: “We need to give the Great Barrier Reef the clean water it needs to recover, and this study shows that clearly. The Queensland Government’s proposals to cut farm pollution need to be passed."

“What this study also says is that these levels of cuts to farm pollution won’t be enough to save corals on outer reefs from the impacts of rising ocean temperatures caused by global warming.

“We have to make sure we are giving the reef the cleanest water we can, while at the same time stopping the digging up and burning of fossil fuels that drive the warming in the reef’s waters."

Schindler said while the study found that corals in areas with poor water quality were more resistant to coral bleaching, due to the low level of light penetrating the turbid water, these corals had slower recovery rates and were more susceptible to disease and Crown of thorns starfish outbreaks.

The study, acknowledged that any marginal bleaching protection corals might get from poor water quality “are probably overwhelmed by the most extreme warming conditions" already seen during 2016 and 2017.

Schindler said it was also important to note the study did not consider any impacts of coral bleaching in the vast and once pristine northern sections of the reef that were hit hardest by extreme ocean temperatures in 2016 and 2017.

Media release. AMCS communications manager Ingrid Neilson 0421 972 731

Water quality mediates resilience on the Great Barrier Reef

M. Aaron MacNeil et al.

Abstract

Threats from climate change and other human pressures have led to widespread concern for the future of Australia’s Great Barrier Reef (GBR). Resilience of GBR reefs will be determined by their ability to resist disturbances and to recover from coral loss, generating intense interest in management actions that can moderate these processes. Here we quantify the effect of environmental and human drivers on the resilience of southern and central GBR reefs over the past two decades. Using a composite water quality index, we find that while reefs exposed to poor water quality are more resistant to coral bleaching, they recover from disturbance more slowly and are more susceptible to outbreaks of crown-of-thorns starfish and coral disease—with a net negative impact on recovery and long-term hard coral cover. Given these conditions, we find that 6–17% improvement in water quality will be necessary to bring recovery rates in line with projected increases in coral bleaching among contemporary inshore and mid-shelf reefs. However, such reductions are unlikely to buffer projected bleaching effects among outer-shelf GBR reefs dominated by fast-growing, thermally sensitive corals, demonstrating practical limits to local management of the GBR against the effects of global warming.

Nature Ecology & Evolution (2019)