Herbicide may have been wrongly convicted as mangrove dieback culprit
Published on 10 October, 2011
The herbicide Diuron may have been wrongly convicted as the culprit in mangrove dieback, according to scientists who have done a systematic review of evidence.
Dr John Abbot and Dr Jennifer Marohasy from CQUniversity say that evidence from field studies suggests the burial of mangrove breathing roots is a more likely causal factor in dieback.
Dr John Abbot and Dr Jennifer Marohasy
They say any contribution from Diuron remains unproven and inconclusive, yet agricultural run-off has been blamed for dieback, influencing government policies, including programs to save the Great Barrier Reef.
Based at the Centre for Plant and Water Science, the scientists have published their findings in an international journal entitled Human and Ecological Risk Assessment. LINK to the article here
Their 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 than measured in rivers has an impact ... been demonstrated."
Dr Marohasy has put the findings into context in a feature article for ON LINE opinion, Australia's e-journal of social and political debate.
She says previous research on Diuron has made it through the peer-review process "perhaps because it plays on a popular Litany - the widespread belief that pesticides are harming the environment and that without political pressure for change we are all doomed".
"Most Australians would expect that policies, including whether to ban a particular pesticide, are based on sound science including the testing of hypotheses, the consideration of alternative causal factors, and an awareness of the relevant scientific literature - not to mention logical argument. Yet such considerations have been lacking in much of the purported scientific discussion concerning potential impacts of land-based activities on the Great Barrier Reef," Dr Marohasy says.