Jury still out on cause of mangrove dieback
Published on 10 August, 2010
Herbicides have been detected in mangrove dieback areas, but does that prove a causal link?
Not necessarily, says CQUniversity researcher Dr John Abbot, who is releasing scientific papers arguing for more proof before people leap to conclusions...
He is also planning his own controlled research experiments.
Dr Abbot has been telling this month's World Soil Congress in Brisbane - and will tell another international conference early next year - that the mere presence of herbicides is not enough to establish a casual link.
"Many studies have focused on measuring the levels of pesticides, particularly herbicides such as diuron, atrazine and simazine, in rivers and coastal areas associated with Great Barrier Reef catchments," he said.
"Modern analytical instruments can detect very low levels of these chemicals. It is known that these chemicals can be transported from agricultural areas, into catchment waterways, particularly during flood events following periods of heavy rainfall."
Dr Abbot said he has been critically reviewing evidence presented in scientific literature which alleges that dieback of mangroves is caused by the presence of pesticides.
"There may be a correlation but the crucial thing is whether there is causation. It is much less certain whether the presence of these chemicals in water or sediments causes environmental harm.
"We've examined claims that herbicides have caused dieback of mangroves in the Pioneer and Fitzroy River estuaries as a case study.
"It's important to consider factors such as bioavailability, and whether appropriate data has been collected to justify causal inferences from any correlations presented.
"Understanding an environmental scenario in the context of the wider scientific literature is essential, as is assessing the significance of any experimental investigations used to support conclusions from field investigations."