Like what you've read?

On Line Opinion is the only Australian site where you get all sides of the story. We don't
charge, but we need your support. Here�s how you can help.

  • Advertise

    We have a monthly audience of 70,000 and advertising packages from $200 a month.

  • Volunteer

    We always need commissioning editors and sub-editors.

  • Contribute

    Got something to say? Submit an essay.

 The National Forum   Donate   Your Account   On Line Opinion   Forum   Blogs   Polling   About   
On Line Opinion logo ON LINE OPINION - Australia's e-journal of social and political debate


On Line Opinion is a not-for-profit publication and relies on the generosity of its sponsors, editors and contributors. If you would like to help, contact us.


RSS 2.0

The Reef, the Reef and nothing but the Reef

By John Ridd - posted Wednesday, 3 December 2008

Years ago I was frequently referred to locally as a “bloody greenie”. That was pleasing as previously I had regularly been referred to as a “fxxxxxg greenie”. Clearly my reputation was improving. It is as a B or F greenie that I watch the recent statements and actions of the governments in respect of the Great Barrier Reef with sadness. Huge resources are now going into fixing reef issues that may exist to some extent while other major environmental problems that certainly exist on land are de-emphasised, neglected and starved of funding.

The GBR is a vitally important area from a biological/conservation standpoint and is also of huge importance economically. Consequently it is worrying when Premier Anna Bligh is quoted as saying “all the evidence is that the Reef was dying …” and “the presence of pesticide residues especially herbicides is widespread in water bodies of the Reef …” Such serious statements merit critical examination.

One of the “high priority” threats to the Reef, according to the Great Barrier Reef Marine Park Authority (GBRMPA), is the Tully River which, like the neighbouring Johnstone River, is in a very wet area and carries a vast amount of water annually.


A few months ago, under the guidance of the CSIRO and at great expense, a Draft Water Quality Improvement Plan (WQIP) for the Tully catchments was released. It states that it was “primarily concerned with reducing sediment, nutrient and pesticide loads in the water entering the GBR”.

The approach used was to draw up Water Quality Objectives (WQOs) for the various inputs that were considered to be risks to the Reef. Then the actual concentrations of those inputs were measured. The Executive Summary of the document, last paragraph, last sentence, states:

A comparison of draft WQOs in inshore marine waters against available data on current water quality in these waters shows that draft WQO’s are met, except for chlorophyll-a [Chl-a].

Yes, you did read that correctly!

Table 1 in the CSIRO document (Table 2 in the Summary) confirms that the situation is really rather good. In view of recent statements by Premier Bligh about pesticides/herbicides (Diuron and Atrazine were specifically mentioned) it is noteworthy that the relevant figures in the Table are:

  • Diuron - WQO 1.0g/L, current condition 0.011g/L;
  • Atrazine - WQO 6.6g/L, current condition 0.004g/L;
  • for Hexazinone the measured concentration is about one two hundredth of the WQO; and
  • Ametryn they could not even detect.

That is surely great news. Except for one possible issue it seems the Tully/Murray/Hull river system does not constitute a threat to the Reef. Of course that means that the idea that the Tully was a “high priority” threat to the Reef was wrong - unless a case can be built on the Chl-a data which showed a concentration of 1.3g/L whereas the WQO target is 2.0 g/L at the mouth and 0.5g/L further off shore.

Chl-a is often a response to nutrient input caused by either riverine input or resuspension of bottom sediments which always naturally contain nutrients. Inshore water Chl-a is hence highly variable depending on the proximity to the shore, weather conditions, and river plumes. It is thus highly debatable whether the measured figure of 1.3g/L quoted in the WQIP is particularly significant.

One may presume that sound scientific principles were used to produce the measured Chl-a figure of 1.3g/L. However there are worrying indications that the authors of the report did not use sound principles in many aspects associated with scientific uncertainty. In science every measurement must be associated with either an explicit or implicit uncertainty. In the WQIP, a model was used to claim that in the year 1850, the Dissolved Inorganic Nitrogen (DIN) exported was 1,160 tonnes with a further 1,129 tonnes of other nitrogen to the Reef. In a scientific document, these figures imply an accuracy of 1 tonne or 0.01 per cent. The models have nowhere near this implied accuracy. Other examples of the lack of attention to uncertainty abound, for example a different model predicts that in the year 2013, the river will export 96,350 tonnes of sediment. In reality the models would be lucky if the uncertainty was less than 10 per cent and could easily exceed 50 per cent. (I can hear my physics teacher in the early 1950s shouting at us on this sort of issue!)

  1. Pages:
  2. Page 1
  3. 2
  4. 3
  5. All

Discuss in our Forums

See what other readers are saying about this article!

Click here to read & post comments.

7 posts so far.

Share this:
reddit this reddit thisbookmark with Del.icio.usdigg thisseed newsvineSeed NewsvineStumbleUpon StumbleUponsubmit to propellerkwoff it

About the Author

John Ridd taught and lectured in maths and physics in UK, Nigeria and Queensland. He co-authored a series of maths textbooks and after retirement worked for and was awarded a PhD, the topic being 'participation in rigorous maths and science.'

Other articles by this Author

All articles by John Ridd

Creative Commons LicenseThis work is licensed under a Creative Commons License.

Photo of John Ridd
Article Tools
Comment 7 comments
Print Printable version
Subscribe Subscribe
Email Email a friend

About Us Search Discuss Feedback Legals Privacy