John Abbot, a research chemist at Central Queensland University, and I, have reviewed the work of Duke and his team. Our findings just published in the international Journal Human and Ecological Risk Assessment detail the many substantial flaws in this research. We explain how concentration of chemical bound to sediment was used as a measure of biological availability when the relevant literature indicates they should have been measuring concentration in solution. In order to get a result in experimental investigations the researchers dosed seedlings with concentrations of chemical orders of magnitude higher than anything found in waterways. Worst still, their experimental design mixed waters from the control and treatments.
The research nevertheless 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.
In the very first report Duke corroborates his concern about an impact from Diuron by calculating a hypothetical value for the amount of Diuron applied to mangroves expressed as the amount of Diuron applied in a particular catchment divided by the area of mangrove in that catchment. Of course Diuron is applied to sugarcane, not mangroves, and only a fraction of the herbicide applied to sugarcane will be transported to the vicinity of mangroves and the area of mangrove will not affect concentration levels. So Duke’s example is not logical. For example, consider a situation where mangroves are growing on opposite sides of a river, if all the mangroves on one side are removed, this would not change the concentration of the herbicide affecting the remaining mangroves.
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.
There is a need for activists and researchers to begin with more open minds and take a more systematic approach, in short there is a need for cultural change as opposed to the current obsession with amassing evidence to support ever more regulation, legislation and the banning of product important to industry.
In the past books were frequently banned. Nowadays we tend to approach this issue with some caution recognising that dangerous ideas are best openly discussed. And history could conclude that many pesticides, including Diuron, are best kept registered and used appropriately, rather than simply banned because of prejudice.
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