“Fickle thy name is” vox populi : puzzle over dung beetles and science reporting

Dung beetle necklace

When I first heard about the proposal to release dung beetles in New Zealand I was really pleased. I grew up in Australia and they have been releasing exotic dung beetles for over 40 years. Dung beetles are regarded as a highly beneficial, safe and successful introduction to Australian agricultural ecosystems.[1] Cows, sheep and horses have all been imposed on Australian and New Zealand ecosystems. They came without the creatures that normally clean up their dung – dung beetles. In Australia, in 1967, it was decided that dung beetles needed to be imported. The reasons for importing dung beetles were 1) to reduce the numbers of flies and biting midges which breed in cow poo, 2) reduce pasture covered in poo (covered pasture can’t grow), 3) reduce the amount of unpalatable grass which grows around cow poo and 4) move the nutrients locked in the cow pat to the soil. Native dung beetles in Australia just couldn’t cope very well with introduced herbivore poo.[2]

Australia is not the only country to introduce exotic dung beetles for management of problems associated with cow poo. They have also been introduced to the United States of America, including Hawaii and South America. They occur indigenously in Africa, Europe, North and South America and Asia. New Zealand has native flightless dung beetles. New Zealand also already has one Mexican dung beetle and at least three small Australian species already.

Recent news articles about the approved forthcoming release of several species of dung beetles to New Zealand have been very negative and somewhat hysterical in tone.[3] [4] There has been a flurry of generally negative public commentary on social media in response.[5]  The source of this negative tone has been researchers at the University of Auckland who disagree with the approval to release dung beetles. Prior to public expression of University of Auckland disgruntlement over dung beetles there has been generally positive media about the introduction of dung beetles to New Zealand.

There was little to no public commentary when the story was covered in the New Zealand Herald in 2009.[6] In 2010 there was another story about dung beetles and this time there were a few shares on social media.[7] Unfortunately I’m not technologically savvy enough to access the comments so I can’t feedback about the responses in this case! The article cites our favourite bug man, Ruud Kleinpaste, who,

 “ doubted the introduction of dung beetles would cause an ecological upheaval, despite earlier animal imports such as possums, rabbits and mustelids that have become expensive problems.

He said it was unlikely that they would compete with the 17 species of native dung beetles in native forests. But he urged caution.

“We have mammals here now and the poo is causing nitrification and causing major pollution on our farms,” he said.

“From that point of view it would be really good to get rid of the poo, it’s a serious job so why not get the experts in to do it. Still, you have to be cautious with what you import and Erma [the Environmental Risk Management Authority] will have some serious thinking to do.”

Zoom forward to 2013 and the EPA (formerly ERMA) have done some serious thinking and the University of Auckland claim they haven’t done enough. The flood of social media shares has increased from 62 to 462. I think the University of Auckland researchers’ and a few others claims warrant more scepticism than any of the recent journalists have given them.

Let’s examine the claims in more detail. The first hint that we are being hoodwinked is this paragraph,

“The three-member authority panel was advised by the dung beetle applicants that the insects would pose no public health risk. This assertion was made simply by ticking a box marked “no” to the question: “Can the organism cause disease, be parasitic, or become a vector for human, animal or plant disease?””

Actually the box that is ticked is a culmination of what is generally a long scientific explanation, by each expert that has been consulted by the three-member authority of the risks or lack thereof. So while the panel is only three members the consultation panel can be extensive. In the case of dung beetles there were a range of dung beetle scientists from around the world.[8] The Ministry of Health in New Zealand was also specifically invited to comment. Given that most current textbooks on Medical Entomology do not even feature dung beetles it isn’t surprising the Ministry of Health wasn’t concerned.

The second misleading claim is around an earlier application to introduce dung beetles,

“At the time, however, the Ministry of Agriculture’s regulatory arm – the predecessor of the EPA – knocked back the application because not enough research had been done to satisfy biosecurity experts that the insects would deliver all the benefits claimed for them.

Guilford maintains nothing has changed in this regard. The difference this time, he argues, was the role of Landcare scientists advocating for the scheme then providing “independent” advice to ERMA.”

There is a nuance worth exploring here. The original claim in 1998 was to import only one species of dung beetle. It was felt by MAF that just one species wouldn’t confer all the benefits which dung beetle introductions overseas have brought. In addition there was concern that dung beetles would compete with earthworms. It wasn’t “not enough research has been done”.[9]

With respect to Guilford’s assertion that “nothing has changed” this isn’t true. For example, regarding earthworms, there has subsequently been research showing that earthworms benefit from dung beetles. They don’t compete.

The NZ Herald article reports that Guildford “maintains the approval process accepted anecdote” but we have to take his word for that because there isn’t any example provided.

A related article in the NZ Herald reports,

“Dr Barnfather, medical officer of health with the Regional Public Health Service, said the evidence was “sufficient to raise concern exotic dung beetles may provide additional vectors for human exposure to significant gastro-intestinal diseases.””

Unfortunately this “evidence” isn’t made available to us. It is presented as an anecdote.

“Potential exposure from beetles contaminating water supplies in homes which collected rain in tanks,……….. had not been adequately researched, Dr Barnfather cautioned.”

Actually there has been research on tank water (and therefore any dung beetles that fall into it) as a source of disease compared to mains water in South Australia where exotic flying dung beetles have been present for about 35 years.[10] The authors conclude that,

“Young children, who were regular consumers of tank rainwater, were at no greater odds of gastroenteritis than those who drank treated public mains water.”

There has also been a systematic review of the safety of tank water versus improved water supplies. There were several studies from countries which have dung beetles and one which doesn’t, New Zealand. They found that there was no difference in disease amongst people who drink tank water compared to those drinking improved water. New Zealand was one of the exceptions. One could capriciously, but somewhat erroneously, conclude that dung beetles actually prevent disease in tank water! However back to my point – the balance of peer reviewed literature would suggest that there isn’t a risk of dung beetles transmitting disease via water tanks. So the onus is very much on Drs Barnfather and Guilford to explicitly refer to peer-reviewed evidence supporting their case.

Guilford publicly berates Landcare for falling into the trap of advocacy and the EPA for relying on them. However the best advocacy is based solely on good evidence and that is what is behind them. In addition the EPA’s consultations extended beyond Landcare scientists.

There are more examples of misleading statements in the press coverage and documentation relating to the dung beetle approval – I could go on…. New Zealand isn’t the experimental territory here, Hawaii, Australia and other countries have had exotic dung beetles for 40 years or more. Peer –reviewed research is expensive. A Google scholar search reveals about 32,000 studies of dung beetles. Dung beetles do have considerable benefits. Do we really need to spend more of our limited public funds on risk assessment of dung beetles? I think there are riskier ventures and more pressing issues that I would like to see my taxes spent on.


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