Barrier Reef still 'pristine', despite concerns: scientist

07 Jun, 2009 09:46 AM

THE Great Barrier Reef (GBR) is in excellent shape - farming and other human activity are not killing the reef, according to James Cook University's reef scientist Dr Peter Ridd.

As a physical oceanographer, his area of interest has been sediment transportation, and his conclusion is there is no significant threat to the reef from human activity and he is adamant cane farmers are not killing the GBR.

"But we are dealing with an important ecosystem so we can't be too complacent," he said.

"If you can minimise your nutrient loads (from farming), you'd be stupid not to, particularly if it reduces your cost of production without harming your crop size."

With regard to proposed legislation, he said whatever priorities are set, they need to be based on good, un-emotive science.

With 25 years of Great Barrier Reef (GBR) research behind him, James Cook University's Dr Peter Ridd has studied the reef ecosystem longer than have most 'eminent' scientists.

He recently told the Australian Cane Farmers Association conference delegates there is no better coral reef ecosystem than the GBR - itias virtually undisturbed, and most is well offshore.

He said there are scientists who say global warming will kill the reef within 60 years.

Some say nutrient and pesticide increases, crown of thorn starfish and ocean acidification will kill it within 30 years, but none of those threats can be substantiated, particularly global warming, as coral is a tropical species which improves in growth rate and health as water temperature rises.

However, getting back to human effects on the reef he said: "We are used to seeing photographs of muddy flood water along the coast and there is no doubt the sediment has increased due to agricultural activity, possibly in the order of 10 times.

"But sediment loads within river outflows are in the order of 1-10 milligrams/litre. They only last a few days each year and they never reach the outer reef.

"By contrast, our research shows the resuspension of sediment by wave action during a 25-knot SE wind is in the order of 10-100mg/L, which happens for a few days every month and it's not sediment that's been deposited in recent times. It's been there since the sea level rose 80,000 years ago.

"The amount that's been added since European settlement is only a very small fraction of what's there. So it would be difficult to make a case that the sediment in a river plume would harm the inshore corals.

"In fact, the top 20cm of sediment on the seabed of the Coral Sea (the depth to which resuspension occurs) contains 500 times the nitrogen and phosphorus of a river plume.

"Biologists tell us the inshore reefs, with only 10 to 20 coral species, are a 'degraded system' because they don't have hundreds of species like the outer reef, but that's like comparing the rainforest in the wet tropics with the desert scrub of Central Australia.

"You can't say the desert scrub is a degraded rainforest, so as the inshore reefs have a different environment, they are composed of corals that are able to thrive in water with high turbidity and nutrient loads.

"Once that was recognised (by the scientists), the focus changed to the nitrogen and phosphorus contained in the run-off from the land and how it affected the whole reef, not just the inshore corals.

"The question needing an answer was: 'Can the results of human activity increase the levels of nutrients across the entire reef for a significant period of time each year?'

"We worked out a set of calculations to discover how long it takes a drop of water to be flushed out of the reef system into the Pacific Ocean.

"We found water in the outer reef was gone within two weeks, and from a river mouth, a month or at the most, two months. And we are not talking about small amounts of water, we're dealing with cubic kilometres of water as the GBR is a very open system.

"Our other calculations, even pushing the limits of probability, show a river plume could increase the N and P levels in inshore waters by 20 percent and in the outer reef by 3pc.

"However, compared to what is already out there and the small time it is in the environment, it is insignificant.

"There is algae growing amongst the corals on the reef that act like legumes and produce more than 20 times the amount of N of a river flow.

"Then there are upwellings of nutrient-rich water from the Pacific that flood over the reef containing 100 times the N and P of the river discharges.

"So it would be virtually impossible to quantify the effect of man-induced increases in nutrients as they are so small."

Regarding herbicides in river water Dr Ridd said the dilution factor ensures it would have no effect on the outer reef but there was a slight possibility it could have an effect on inshore reefs.

"But we can't point to any single reef and say it is significantly different from what is was when Captain Cook sailed up the coast.

"It may have changed due to a flood, a cyclone or coral bleaching, but it repairs itself over time.

"By contrast, on the land we can see erosion, introduced weeds and feral animals all causing environmental degradation and funding for research and control is being reduced, whereas funding for the GBR, where no degradation is measurable, is increasing and I would like to see that reversed.

"Also, unlike most other coral reef systems of the world, herbivorous fish are not harvested on the GBR – our catch is all carnivorous fish, which leaves the herbivorous species to keep algae under control and the reef is in pristine condition."

North Queensland RegisterSource: http://www.northqueenslandreg...
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Green farmer
8/06/2009 6:53:21 AM

Good common sense arguments based on substantive knowledge and years of scientific research! Why is it that the State Government hasn't heard from this scientist before making their 'vote winning' (in urban areas) decisions about what farmers are doing wrong and what should be done. It seems to me that once again they are relying on inadequate advice from senior bureaucrats and/or green groups who claim to have all the answers without any real consultation with stakeholders and the most appropriate scientist. This is decision making the way vegetation management decisions were made all over again!
8/06/2009 8:08:25 AM

A close friend who has worked for Parks and Wildlife or similar, in three states recently scuba dived on the reef and relayed the remarks of their instructor who backs this up. He said the reef is in excellent condition and the hoo-ha was just that.
8/06/2009 10:05:56 AM

Well, once again we can see how little we know and how great our ignorance is. We can be easily duped by the political views of the very few that are prepared to make a lot of noise. We need to be careful that our anxiety does not turn our nation's interests into chaos.
8/06/2009 8:35:27 PM

Green doomsayers should hang their heads in shame. The general public is sick and tired of their rhetoric. That includes the gas baggers in the Australian Institute of Marine Science.
Jon Brodie
15/06/2009 4:43:45 PM

This article is a very personal view of the situation by Peter Ridd, not supported by any large body of scientific publications, but contradicted by a large body of published papers which show there is a serious problem. These papers are summarised in the Consensus Statement and its supporting document. Here you can find hundreds of papers which support the consensus view as to the extent of the problem and possible moves towards solving it: brary/pdf/publications/Scie ntific%20Consensus%20Statement%20 on%20Water%20Quality%20in%2 0the%20GBR.pdf A few direct corrections to some of Peter’s points are below: 1. Suspended sediment concentrations in rivers as they flow in to the GBR are in fact typically between 200 milligram per litre for relatively ‘clean’ rivers (e.g. Tully) to 1000 mg/L for ‘dirty’ rivers (e.g. Burdekin). While sediment concentrations may fall to 1 – 10 mg/L in the river plume eventually this occurs tens to hundreds of kilometres from the river mouth. 2. Inshore reefs are not naturally ‘degraded’ and often those in close to pristine conditions (e.g. off Cape York) have hundreds of species of coral; in fact more species than most offshore reefs. Even in their degraded condition reefs on Magnetic Island, in the Palm Islands and in the Whitsundays have many more species than the 10 to 20 mentioned by Peter Ridd. 3. In response to: 'Can the results of human activity increase the levels of nutrients across the entire reef for a significant period of time each year?' my response is: Instead of modelling this situation other reef scientists have been out measuring this since 1990 and have shown conclusively that nutrient concentrations in flood plumes are increased above natural by factors of 10 to 100 times for periods of one to eight weeks. This is all published work and completely refutes Peter Ridd’s modelled calculations.
John Davis
12/07/2009 10:42:21 AM, on North Queensland Register

Just as the tobacco industry found "scientists" who would say that tobacco causes no harm, and the petroleum industry found "scientists" who said that pumping carbons into the air causes no harm, so various industries have found people like Peter Ridd to give them a feeling of clean conscience so they can continue making money while damaging various ecosystems and the planet on which we all depend. As a diver, scientist and underwater photographer, I can assure you that the GBR is not in good shape, it is dying, and its death is due to human activities. As far as "un-emotive" science, what Ridd means is science that bows to the god of greed and industry. "Emotion" is a code word for values. Those of us who value clean air, clean water, native species, and the beauty of earth are guilty of "emotive" thinking because we still have a heart and a conscience. People like Ridd have one thing: dollars signs in their eyes.
20/07/2009 12:08:21 PM, on North Queensland Register

Dear John, the only possible way of keeping everything as you say, is for ALL humans to be moved into space - the moon looks good!! Nothing to wreck there...but then again the "Save the moon" mob might have other ideas!!! Like any emotive argument from the green-groups (dying, greed, death, human activities) and the rest of the code words, the truth about the whole planet is probably somewhere in between the 2 arguments!
24/07/2009 8:31:58 PM, on North Queensland Register

Dear John, dollar signs? Being the son of a cane grower I can tell you there is no money in sugarcane for those who choose to over irrigate, over apply fertilisers and use pre-emergent herbicides such as atrazine, diuron & ametryn. In response to the stewardship concerns that most Burdekin farmers hold for the nearby coral reefs you would find that most apply minimum fertiliser at the peak nutrient usage times, only use non residual herbicides, and monitor the nutrient runoff that actually comes from their paddocks so as to improve future practice. These voluntary best practices were developed and implemented by funding from the Federal government who wished to not only preserve the reef but the communities adjacent to them as well. The Bligh government just wishes to publicly demonize the farmers of the north to create an enemy that her government may oppose as a political stunt. So far Bligh has done little but introduce legislation that will cost growers and seek to enforce the current voluntary best practice which will eventually be outdated by future research. In conclusion Anna Bligh has an Arts Bachelor, Peter Ridd is an oceanography professor of 25years, I know who I trust.


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Pleased that common sense has prevailed. Being close to the policy makers cannot be underestimated
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JohnCarpenter, The lamb and mutton job is going okay- we must be doing some things right.
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Spot on X. Let the Chinese buy as long as we can buy freely in China