Drought, dung and destruction

Dung beetles may not be the first animals to come to mind when thinking about the organisms impacted by the 2019-20 intense bushfires - but perhaps they should. We were recently in Northeast NSW to determine the impacts on dung beetle populations.

We were driving through the bush with 4kg of the freshest kangaroo dung available, frozen in the back of our 4WD. There was good reason for this. We are part of a large Federal Government-funded project examining the impacts of the intense 2020 fire season on invertebrates. When you think of all the organisms impacted by last year’s intense bushfires, dung beetles might not come to mind - but perhaps they should.

These pintsized poo-piling powerhouses perform extremely important ecosystem functions. By gathering and burying dung, dung beetles help cycle nutrients, taking waste on the surface and making it available to plants, animals and fungi underground. They are so efficient at this, that they reduce the availability of dung to other insects and help regulate their numbers. The process of digging burrows also aerates soil, making oxygen available to plant roots and underground microbial communities, as well as allowing water to soak in rather than just flowing across the surface. This intricate relationship with many other plants and animals can make dung beetles a great indicator of ecosystem health overall.

Australia has about 550 species of native dung beetle, many of which are flightless. The evolution of flightless characteristics is typically due to predictable and stable environments. Therefore, it’s no surprise that most of Australia’s flightless dung beetles are found in wet rainforests where there were rarely fires to escape from. Unfortunately, this is rapidly changing.

Increasingly severe and prolonged droughts have impacted forests across Australia, and led to the burning of areas rarely, if ever, touched by fire. These areas are inhabited by plant and animal species that have not evolved to be fire tolerant and may be much more severely impacted by fires than others. Even the iconic Australian Eucalyptus tree, adapted over millions of years to withstand bushfires, is having trouble adapting to these extreme temperatures and periods of dry, hot weather. We regularly drive past vast areas of ghostly, black-stemmed terrain that was once dense Eucalypt forest – a stark reminder of our rapidly changing climate. Australia is experiencing fires that are too intense for some established gumtrees to survive, or too frequent to allow new saplings to reach maturity.

The effect of these changing fire regimes on our native dung beetle fauna is poorly understood. Dung beetles are an integral part of Australian forests and understanding how their populations are impacted is important if we are to predict how forests will adapt to more frequent, more intense fires. We set pitfall traps baited with fresh dung in burnt and unburnt locations, returning the next morning to collect the trapped beetles. It’s only early days, but initial results show that burnt areas contain fewer dung beetles, even a year after the fires. If we are to help conserve our native plants and animals in the face of climate change, research projects on overlooked but foundational groups like dung beetles are vital.

Aidan Runagall-McNaull, Technical Officer, Entomology, Australian Museum Research Institute

Dr Chris Reid, Research Scientist, Entomology, Australian Museum Research Institute

Acknowledgements:

We are grateful to Symbio Zoo, Helensburgh for the roopoo, the National Parks and Wildlife Service, NSW, for access to their estate, to our colleagues Professors Shawn Laffan and Gerry Cassis in University of New South Wales, for leading this project, and to the Federal Government for funding this project.