Anyone who spends time on the River Murray knows that the introduced pest, the bottom-feeding European Carp, dominates the river ecosystem and has all but destroyed our native species of fish. According to the ABC, carp make up 80% of the fish biomass and cause $500 million of environmental damage each year.
To counter the carp’s dominance, the Federal Government plans to to release a strain of herpes, cyprinid herpesvirus-3, into the river system at the end of 2018. This disease supposedly will target only the carp, leaving other species unaffected.
Australia doesn’t have a great track record when it comes to ecological interventions. Perhaps the best known example of this was the introduction of Hawaiian cane toads to North Queensland back in 1935. The cane toad was introduced to biologically control the grey-backed cane beetle, a pest which was degrading local sugar cane crops.
It was an unmitigated disaster. The cane toad population exploded, and not only did it bring many adverse effects to the local environment, such as the toxic poisoning of predators, it also failed to curb the degradation of sugar cane by the cane beetle. Now the cane toad and its steady march across the north of Australia has become a far bigger problem than the species it was supposed to control.
Other biodiversity disasters in Australia include the introduction of the fox and the rabbit for sporting purposes back in the 1850s, and the introduction of the invasive Indian Myna bird to control locust plagues.
To be fair, we’ve also had some success. The introduction of dung beetles has reduced bush fly number by 90%, as well increasing soil fertility and quality by recycling the dung back into the soil.
So how are we likely to fare with the ‘rabbits of the river’, the European Carp?
Research is now underway to work out how the ecosystem will change as a result of the proposed intervention. Apparently, small changes in oxygen levels can have big ramifications for native wildlife, so researchers at the University of Adelaide have been putting dead carp into 800-litre tubs of water to try to measure the amount of oxygen the decomposing fish use up. Initial indications are that the death of the carp will significantly change the oxygen level of the water, putting other species at risk. There’s also the problem of thousands of tonnes of rotting fish carcasses that will sink to the bottom of the river and its tributaries. How will this impact the system?
Systems thinking giant Donella Meadows says that the best way to avoid the trap of escalation – where multiple ‘stocks’ (in this case, fish species) fight against one another for primacy – is to avoid getting into it in the first place. That’s clearly not possible now, as the carp already dominates the river system to the detriment of other species. So what is now to be done? Whilst there is still some hope of saving the native species, some form of intervention is appropriate. But in what form? Is a herpes strain the right answer?
As a newly-minted system thinker, I can’t help but think that rushing in is fraught with danger. The Federal Government has issued an intervention date (the end of 2018) and the issue has been used for party political purposes in recent months. At the same time, the research scientists are recording adverse test results. This is cause for concern.
Any intervention will need to be undertaken with extreme caution and care. The river system is a delicate, complex holarchy of millions of different ecological sub-systems. A small change in one sub-system can have disproportionate effects elsewhere in the holarchy. And those effects could be entirely unpredictable, just as the effects of the cane toad where not foreseen in Queensland.
The ‘river’ system also belongs to and impacts upon many external, non-ecological systems. The ‘river’ represents the livelihood for many Australians along its wide expanse, from its origins in the Great Dividing Range, to its mouth at Goolwa. A failed intervention to kill the carp could have a significant impact upon these seemingly-unrelated—but in actuality, entirely interdependent—systems. The stakes are high.
Before intervening, Meadows exhorts us to first ‘get the beat of the system’, to ‘listen to the wisdom of the system’ and to ‘expand time horizons’ – it’s extremely important that no intervention is enacted without first undertaking an exhaustive study of its potential effects. The Federal Government only has one shot at this.
Source: ABC Website, http://mobile.abc.net.au/news/2016-08-14/herpes-carp-kill-in-river-murray-ecosystem-may-sap-oxygen/7731892
EXTRA: How Wolves Change Rivers
We watched this video in our systems thinking class. It provides some understanding of how small changes in ecosystems can have disproportionate effects elsewhere in the holarchy of systems. Well worth a look.