Which Pesticides Should be Banned?

NICK Heath is worried about the future of the Great Barrier Reef.  He has a Bachelor of Commerce and after ten years in business and consulting, moved into political and policy advice for government.  He’s now the national program leader for water at WWF-Australia.   He’s been spearheading the ongoing WWF campaign to ‘Save the Great Barrier Reef’. [1]

As part of this campaign WWF wants the herbicide Diuron banned.  Heath recently told journalist Brian Williams at the Courier Mail that he accepted that government would probably ban Diuron, but he was disappointed about further delays. [2]

Why does Heath want Diuron banned?

Recently, on ABC Radio National he said, “Don’t ask WWF for an endorsement of what a safe pesticide is.  I’m not qualified.  But that is why we need a better regulatory system.” [3]

As part of the same program, Munro Mortimer from the National Research Centre for Environmental Toxicology said, “Some of the chemicals that have been banned in overseas countries particularly in Europe…  some of these bans probably relate more to politics and popular perceptions rather than science.  Because that is the way that these things tend to happen. Quite often governments respond to political pressure regardless of whether they are supported by science or not.”

Mortimer made many other relevant and insightful comments during the program but they were mostly ignored by Paul Barclay, the host of the show.  Barclay seemed more interested in encouraging Nick, who apparently has no idea what a safe pesticide is, to suggest more be banned.

And this has been about the level of the discussion for about the last ten years – since WWF first launched its ‘Safe the Great Barrier Reef Campaign’ in 2001.   And not just the public discussion, but from my experience also much of the technical discussion.

John Abbot, a research chemist at Central Queensland University, and I recently reviewed the work of Norm Duke who published peer-reviewed papers and reports claiming Diuron killed mangroves.  Our paper has just come out in the international peer-reviewed journal Human and Ecological Risk Assessment, Volume 17, pages 1077-1094.   In the paper we explain that while Duke’s work influenced government policies to ‘Save the Great Barrier Reef’ this same research is fundamentally flawed. [4]

If you would like a pdf copy of our paper and don’t have access to a technical library, please email me at jennifermarohasy@jennifermarohasy.com.



1. Nick Heath at Linked In.  Accessed October 5, 2011.

2. Williams B. 2011. Farm chemical diuron found in Great Barrier Reef catchment at levels 50 times higher than those considered safe.  Courier Mail.  http://www.couriermail.com.au/news/queensland/farm-toxins-flow-to-reef/story-e6freoof-1226143002578

3. Barclay P. 2011. Our waterways: are we poisoning them and ourselves? Australia Talks, ABC Radio National. June 28, 2011.  http://www.abc.net.au/rn/australiatalks/stories/2011/3243560.htm

4. Abbot J., Marohasy J. 2011.  Has the herbicide Diuron caused mangrove dieback? A re-examination of the evidence.  Human and Ecological Risk Assessment. Volume 17,  Pages 1077-1094.

Abstract of our paper…

The claim that the herbicide Diuron in agricultural runoff caused dieback of the grey mangrove (Avicennia marina) in Central Queensland, Australia, has influenced government policies including programs to save the Great Barrier Reef. Several investigations on mangrove dieback in Central Queensland river estuaries have been published during the past decade.However, proof of a causal link between mangrove dieback and Diuron remains inconclusive. This study presents a systematic review of the evidence using Hill’s Criteria of Causation. Our review shows that using concentrations of the chemical bound to sediment as a measure for biological availability in either glasshouse or field studies is inappropriate. The appropriate measure is Diuron concentration in solution and this parameter bears no simple relationship to concentration bound to sediment, and is not strongly correlated with mangrove health. Only when the herbicide is applied in experimental investigations at many orders of magnitude higher thanmeasured in rivers has an impact on A. marina been demonstrated. Evidence from field studies suggests burial of pneumatophores, the plant’s breathing roots, following flood events is a more likely causal factor in mangrove dieback, whereas any contribution from Diuron remains unproven.

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10 Responses to Which Pesticides Should be Banned?

  1. kuhnkat October 10, 2011 at 7:18 am #

    Sounds like the same type of issue our friend over at JunkScience. com is continuously hitting on. Poor epidemiological type studies are only an indicator of whether more indepth studies should be done, not whether there is an actual connection.

  2. Luke October 10, 2011 at 10:42 am #

    Duke’s work is of minor consequence to the current situation. Old hat. Lots of water and herbicides under the bridge since then.


  3. dennis webb October 10, 2011 at 11:00 am #

    Luke Mate, Which is the now relevant research? Links and references please! Where’s the evidence for an impact from Diuron on the Reef? Heath seems to be all about generalities and moralizing… typical WWF yadda yadda yadda

  4. jennifer October 10, 2011 at 12:48 pm #

    Luke, I think you will find if you read the references you provide that there is a disconnect between concentration levels found in waters of the GBR and concentrations used in the experiments.

  5. Luke October 10, 2011 at 7:26 pm #

    Jen – merely updating your debate. And issues of concern are cumulative impacts of sediment, nutrients, herbicides. As the last cite above – “Water quality as a regional driver of coral biodiversity and macroalgae on the Great Barrier Reef” suggests.

    Additionally sediment, nutrients and herbicides on the reef are wasted resources – they should be on sugar paddocks and grazing lands. Farming technology and agronomic techniques have much to offer.

  6. jennifer October 10, 2011 at 8:03 pm #

    Luke the presence of parts per trillion of a pesticide in reef water (and it is at this level they are finding chemical) could be simply interpreted as evidence of a modern agricultural industry onshore.

    And in banning Diuron, WWF is potentially increasing the potential for sediment runoff because Diuron is an important component of minimum tillage systems in sugar production. These are systems that have significantly reduced sediment loss.

    Indeed, levels of sediment loss from areas that now Green Cane TrashBlanket (GCTB) are incredibly low… Go Google some figures and have a go at finding an old report by the Australian Conservation Foundation about the need for farmers to move to GCTB and see they moved quicker than anticipated… I think the report was called ‘Keeping it Sweet’.

  7. Luke October 11, 2011 at 12:12 am #

    Jen – sediment mainly comes grazing lands and broad scale cropping not sugar fields. And plenty of it vastly exceeding pre-European levels.

    Reef science has moved on with investigation of land management practices and monitoring. It’s worth getting updated.

  8. Bronson October 11, 2011 at 5:11 pm #

    I think you’ll find that’s what Jen just said pre and post GCTB and the speed farmers moved to GCTB saw a dramatic drop in sediment loss. Maybe you should get updated?

  9. Luke October 11, 2011 at 7:35 pm #

    What rot and a ruse argument? Evidence is where that there is any noticeable effect on sediment loads onto the reef? It’s not even the major source of sediment – update yourself Bronson.

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