Bushfires left millions of animals dead. We should use them, not bury them.
Bushfires this season have left in their wake, their carcasses dotting the blackened landscape.
Adding to the toll, farmers are being forced to euthanise听injured and starving livestock听and there are also calls to cull feral animals in fire-affected areas,听including by aerial shooting.
The carcasses have already been flagged as a听potential biosecurity threat, and the Australian Defence Force is tasked with collecting and burying the dead in mass graves.
There鈥檚 logic in this. Carcasses can harbour nasty diseases such as听botulism听that threaten human, livestock and wildlife health. They also provide food for invasive pests like feral cats and red foxes.
But carcasses can play a positive role as landscapes recover from fire, providing rich nutrients for other native animal, microbial and plant species.
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Carcasses provide important food sources to native animals, such as the lace goanna. Photo: Emma Spencer
The Morrison Government has announced a $50 million package to help wildlife and habitat recover from the fires, and听听and environment groups to get advice on the recovery process.
We suggest this process should examine carcass disposal methods other than burial, such as composting 鈥� effectively 'recycling' the dead. It should also involve monitoring the carcasses that remain to understand both their positive and negative roles in fire-ravaged areas.
The positives: carcasses feed the living
Carcasses feed a range of native animals, including听听and听. Post-fire, they can provide an alternative source of food for struggling native predators and pollinators. And feeding hungry predators with carcasses could redirect them away from听.
Carcasses also feed insects such as flies, ants, beetles, and their larvae, and support important ecological processes such as听pollination.
As they decompose, nutrients leach from carcasses into the surrounding environment and create 'halos' of greenery in the landscape, where vegetation thrives around carcass sites. Their influence on soil and plant communities can听.
Vegetation growth 鈥榟alo鈥� around a kangaroo carcass. When animals die their nutrients can influence the landscape for years. Photo: Emma Spencer
The negatives: spreading disease and sustaining feral animals
. But some carcasses also harbour harmful pathogens that bring disease.
For a disease outbreak to happen, the animal must generally have already been carrying dangerous infectious agents, like Anthrax or the Hendra virus, before they died. And many of these pathogens will not survive long on dead hosts.
Leaving carcasses out in the open can also feed introduced predators such as听听and听, putting small native animals at risk. Some weeds thrive in the听.
Introduced insects like the European wasp,听听following fires in Kosciuszko National Park, also take advantage of carcass resources. These wasps are highly aggressive and听.
How long does a carcass stick around?
We know very little about the ecological role of carcasses in fire-affected areas, and it鈥檚 important that more research is carried out.
We know听听than other carcasses and harbour different types of insect scavengers.
However the recent fires are likely to have wiped out entire scavenger communities, including larger scavengers like dingoes and eagles, that help to clean our landscapes of dead animals.
The effects of this are unknown, but could mean that carcasses stick around in the environment for prolonged periods, even months.
A feral cat scavenging on an animal carcass. Animal carcasses could increase the number of feral predators. Photo: Emma Spencer
Finding the right solution to a grisly problem
As climate change accelerates the number of natural disasters and听mass animal deaths, more thought and planning must be put into carcass management.
In Australia, carcasses are often dealt with by not dealing with them: they鈥檙e left to rot. This happened for听almost 100 feral horses听that died last year at an empty water hole during a heatwave.
Animals culled in national parks and on farmlands are also often left to decay, untouched, as are the many dead animals that commonly line our country roads. But in landscapes where feral species are common, or where livestock or people are likely to encounter carcasses, leaving them alone isn鈥檛 the best option.
Carcasses are more often buried following disease outbreaks or when livestock die. We saw this听, where thousands of drowned cattle were buried in mass graves.
Burial is a relatively inexpensive, fast and effective method of dealing with the dead. But it must be done carefully to avoid polluting groundwater sources and causing nutrients like nitrogen to build up.
Burying carcasses can also be compared to sending rubbish to the tip. Breakdown will be slow, and no useful end product is created.
A more useful option
An alternative option is to 'recycle' carcasses by composting them. Composting can accelerate the decomposition of animal tissues and is environmentally friendly, capturing nutrients.
Composting kills most pathogens, whereas burial just moves the problem underground. It also suppresses smelly odours and doesn鈥檛 attract scavengers. The usable organic material resulting from the composting can also be applied to nutrient-poor soil.
Getting used to the 鈥榶uck鈥� factor of carcasses. Photo: Emma Spencer
Composting can be time-consuming and听. It requires careful monitoring of temperature and moisture content to ensure all disease-causing pathogens are killed, and odours听.
There鈥檚 also a 'yuck' factor and the public would probably need convincing for the method to be widely adopted.
But whatever option we choose, it鈥檚 clear there鈥檚 more we can do with carcasses than simply burying them.
This article was written by Emma Spencer, a PhD student听with the at the 爆料王,听 from the听爆料王 School of Life and Environmental Sciences, from Australian National University and , lead investigator in the Global Ecology Lab听at the 爆料王.
It was first published on The Conversation as听
