Jacqueline Beggs: Dung beetles pose threat to us and our wildlife

There are too many unanswered questions about the impact the beetles would have on New Zealand. Photo / Supplied

Introducing new species is a valuable tool for controlling pests, but although there have been some stunning successes, it can go badly wrong.

New Zealand's approach is to proceed with caution, and many researchers have done and are doing just that. We rely on the EPA (previously ERMA) to be the gatekeepers of introductions; balancing the demand for new organisms to control pests or improve production against the risk of letting in organisms that run amok (think of the kiwifruit catastrophe, PSA).

Using exotic dung beetles to process pastoral dung illustrates the balancing act. Do the risks outweigh the benefits?

The recent debate about releasing 11 exotic dung beetle species in New Zealand has focused on the disease risk to humans, rather than the impact on native New Zealand ecosystems.

I submitted to ERMA against the proposal, arguing that we do not have sufficient evidence to make a decision. In the 10 minutes I was allocated at the hearing, I highlighted my concerns about the ecological consequences of interfering with poorly understood decomposition systems which carry out critically important roles such as nutrient cycling.

We do not know what might eat dung beetles in New Zealand or what the flow on effects might be. Might the number of rats or other introduced predators increase if they snack on large exotic dung beetles? We have plenty of evidence of what will happen to our beleaguered native wildlife if introduced predator numbers increase. Exotic dung beetles provide a ready food supply for cane toads, contributing to their invasion over vast areas of Australia; an unintentional consequence of the release of dung beetles there.

The applicants claimed native and exotic dung beetles would not overlap because our natives are confined to large tracts of native forest, mostly feeding on decaying matter, while the exotics would be confined to pasture, feeding on dung. This was supposition - the diet and habitat of our native dung beetles was unknown at the time. Subsequent research has shown the applicants were wrong - some native species inhabit forest fragments and readily feed on exotic dung. It was already known that unexpectedly the Mexican dung beetle has encroached into our native forest fragments. Perhaps other exotic dung beetles will do the same, leaving our native beetles to compete with the new arrivals.

The applicants used mathematical models to demonstrate the need for 11 dung beetle species so that all pastoral regions of New Zealand will become inhabited by dung beetles. But they used an old model that is now seldom used as it has been shown to perform poorly. They omitted to assess one of the species. Even so, their models show that only four species were likely to establish. So, either they don't believe their own modelling, or they are willing to gamble funding on a venture that is unlikely to succeed for most species.

One of the key problems with the current EPA process is inadequate selection of independent reviewers. In the case of dung beetles, review was sought from dung beetle specialists and not broadened to include other disciplines with different perspectives. The process relied heavily on Landcare Research ensuring that the right people had been consulted and engaged. I know many experts who were unable to give the required attention to this proposal, but assumed the ERMA system would be robust, independently reviewed and any valid concerns would be given due weight. Given the negative reaction that has now emerged, I think it is apparent that this was not the case.

After the ERMA decision and the emergence of more concerns about the proposed release, Landcare Research established a technical advisory group (TAG) on dung beetles. I was invited to join this TAG and briefly participated, but resigned once I realised that one of the stated outcomes of the group was to achieve "national agreement that releasing is the right thing to do". I object to the advocacy role implicit in such a statement and certainly it compromises the objectivity of science if the outcome has already been decided. Furthermore, I have concerns that the research was in fact a de facto release programme since there were no plans to destroy any beetles that may have escaped into the ground during the research.

I am not against biological control or the introduction of dung beetles per se, but I am against their introduction without rigorous science to inform the decision. There are too many important unanswered questions to proceed with a release that potentially has long-term consequences for New Zealand. What is the rush? Can we not take the time to make sure we get this right? I look forward to the evolution of a more robust, transparent and objective process.

Associate Professor Jacqueline Beggs lectures in entomology and conservation ecology at the University of Auckland.