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Pest plants and animals cost Australia around $25 billion a year – and it will get worse



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Corey J. A. Bradshaw, Flinders University and Andrew Hoskins, CSIRO

Shamefully, Australia has one of the highest extinction rates in the world.
And the number one threat to our species is invasive or “alien” plants and animals.

But invasive species don’t just cause extinctions and biodiversity loss – they also create a serious economic burden. Our research, published today, reveals invasive species have cost the Australian economy at least A$390 billion in the last 60 years alone.

Our paper – the most detailed assessment of its type ever published in this country – also reveals feral cats are the worst invasive species in terms of total costs, followed by rabbits and fire ants.

Without urgent action, Australia will continue to lose billions of dollars every year on invasive species.

Feral cats are Australia’s costliest invasive species.
Adobe Stock/240188862

Huge economic burden

Invasive species are those not native to a particular ecosystem. They are introduced either by accident or on purpose and become pests.

Some costs involve direct damage to agriculture, such as insects or fungi destroying fruit. Other examples include measures to control invasive species like feral cats and cane toads, such as paying field staff and buying fuel, ammunition, traps and poisons.

Our previous research put the global cost of invasive species at A$1.7 trillion. But this is most certainly a gross underestimate because so many data are missing.



Read more:
Attack of the alien invaders: pest plants and animals leave a frightening $1.7 trillion bill

As a wealthy nation, Australia has accumulated more reliable cost data than most other regions. These costs have increased exponentially over time – up to sixfold each decade since the 1970s.

We found invasive species now cost Australia around A$24.5 billion a year, or an average 1.26% of the nation’s gross domestic product. The costs total at least A$390 billion in the past 60 years.

Increase in annual costs of invasive species in Australia from 1960 to 2020. The predicted range for 2020 is shown in the upper left quadrant. Note the logarithmic scale of the vertical axis.
CJA Bradshaw

Worst of the worst

Our analysis found feral cats have been the most economically costly species since 1960. Their A$18.7 billion bill is mainly associated with attempts to control their abundance and access, such as fencing, trapping, baiting and shooting.

Feral cats are a main driver of extinctions in Australia, and so perhaps investment to limit their damage is worth the price tag.

Tasmania’s bane — ragwort (Senecio jacobaea)
Adobe Stock/157770032

As a group, the management and control of invasive plants proved the worst of all, collectively costing about A$200 billion. Of these, annual ryegrass, parthenium and ragwort were the costliest culprits because of the great effort needed to eradicate them from croplands.

Invasive mammals were the next biggest burdens, costing Australia A$63 billion.

The 10 costliest invasive species in Australia.
CJA Bradshaw

Variation across regions

For costs that can be attributed to particular states or territories, New South Wales had the highest costs, followed by Western Australia then Victoria.

Red imported fire ants are the costliest species in Queensland, and ragwort is the economic bane of Tasmania.

The common heliotrope is the costliest species in both South Australia and Victoria, and annual ryegrass tops the list in WA.

In the Northern Territory, the dothideomycete fungus that causes banana freckle disease brings the greatest economic burden, whereas cats and foxes are the costliest species in the ACT and NSW.

The three costliest species by Australian state/territory.
CJA Bradshaw

Better assessments needed

Our study is one of 19 region-specific analyses released today. Because the message about invasive species must get out to as many people as possible, our article’s abstract was translated into 24 languages.

This includes Pitjantjatjara, a widely spoken Indigenous language.



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Australia’s threatened species plan has failed on several counts. Without change, more extinctions are assured

Even the massive costs we reported are an underestimate. This is because of we haven’t yet surveyed all the places these species occur, and there is a lack of standardised reporting by management authorities and other agencies.

For example, our database lists several fungal plant pathogens. But no cost data exist for some of the worst offenders, such as the widespread Phytophthora cinnamomi pathogen that causes major crop losses and damage to biodiversity.

Developing better methods to estimate the environmental impacts of invasive species, and the benefit of management actions, will allow us to use limited resources more efficiently.

Phytophthora cinnamomi, a widespread, but largely uncosted, fungal pathogen.
Adobe Stock/272252666

A constant threat

Fall armyworm, a major crop pest.
Adobe Stock/335450066

Many species damaging to agriculture and the environment are yet to make it to our shores.

The recent arrival in Australia of fall armyworm, a major agriculture pest, reminds us how invasive species will continue their spread here and elsewhere.

As well as the economic damage, invasive species also bring intangible costs we have yet to measure adequately. These include the true extent of ecological damage, human health consequences, erosion of ecosystem services and the loss of cultural values.

Without better data, increased investment, a stronger biosecurity system and interventions such as animal culls, invasive species will continue to wreak havoc across Australia.

The authors acknowledge the Traditional Owners of the lands on which they did this research.

Ngadlu tampinthi yalaka ngadlu Kaurna yartangka inparrinthi. Ngadludlu tampinthi, parnaku tuwila yartangka.The Conversation

Corey J. A. Bradshaw, Matthew Flinders Professor of Global Ecology and Models Theme Leader for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders University and Andrew Hoskins, Research scientist CSIRO Health and Biosecurity, CSIRO

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Fly infertility shows we’re underestimating how badly climate change harms animals


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Belinda van Heerwaarden, The University of Melbourne and Ary Hoffmann, The University of MelbourneEvidence of declining fertility in humans and wildlife is growing. While chemicals in our environment have been identified as a major cause, our new research shows there’s another looming threat to animal fertility: climate change.

We know animals can die when temperatures rise to extremes they cannot endure. However, our research suggests males of some species can become infertile even at less extreme temperatures.

This means the distribution of species may be limited by the temperatures at which they can reproduce, rather than the temperatures at which they can survive.

These findings are important, because they mean we may be underestimating the impacts of climate change on animals – and failing to identify the species most likely to become extinct.

two flies mating on a leaf
The distribution of some species may be limited by the temperatures at which they can reproduce.
Shutterstock

Feeling the heat

Researchers have known for some time that animal fertility is sensitive to heat stress.

For example, research shows a 2℃ temperature rise dramatically reduces the production of sperm bundles and egg size in corals. And in many beetle and bee species, fertilisation success drops sharply at high temperatures.

High temperatures have also been shown to affect fertilisation or sperm count in cows, pigs, fish and birds.

However, temperatures that cause infertility have not been incorporated into predictions about how climate change will affect biodiversity. Our research aims to address this.



Read more:
Male fertility: how everyday chemicals are destroying sperm counts in humans and animals

eggs on straw
High temperatures can affect bird reproduction.
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A focus on flies

The paper published today involved researchers from the United Kingdom, Sweden and Australia, including one author of this article. The study examined 43 species of fly to test whether male fertility temperatures were a better predictor of global fly distributions than the temperatures at which the adult fly dies – also known as their “survival limit”.

The researchers exposed flies to four hours of heat stress at temperatures ranging from benign to lethal. From this data they estimated both the temperature that is lethal to 80% of individuals and the temperature at which 80% of surviving males become infertile.

They found 11 of 43 species experienced an 80% loss in fertility at cooler-than-lethal temperatures immediately following heat stress. Rather than fertility recovering over time, the impact of high temperatures was more pronounced seven days after exposure to heat stress. Using this delayed measure, 44% of species (19 out of 43) showed fertility loss at cooler-than-lethal temperatures.



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The researchers then matched these findings to real-world data on the flies’ distribution, and estimated the average maximum air temperatures the species are likely to encounter in the wild. They found the distribution of fly species is linked more closely to the effects of high temperature on male fertility than on temperatures that kill flies.

These fertility responses are crucial to species survival. A separate study led by one author of this article, using simulated climate change in the laboratory, showed experimental populations of the same flies become extinct not because they can’t survive the heat, but because the males become infertile. Species from tropical rainforests were the first to succumb to extinction.

The prediction that tropical and sub-tropical species may be more vulnerable to climate change is not new. But the fertility findings suggest the negative impact of climate change may be even worse than anticipated.

Flies on a stick
The research found fly fertility is affected at lower-than-lethal temperatures.
Shutterstock

What does all this mean?

Some animals have adapted to minimise the effect of high temperature on fertility. For instance, it’s thought testes in male primates and humans are externally located to protect the developing sperm from excessive heat.

As the planet warms, animals may further evolve to withstand the effects of heat on fertility. But the speed at which a species can adapt may be too slow to ensure their survival. Our research has shown both tropical and widespread species of flies could not increase their fertility when exposed to simulated global warming, even after 25 generations.

A study involving beetles also indicates fertility damage from successive heatwaves can accumulate over time. And more work is needed to determine how other stressors such as salinity, chemicals and poor nutrition may compound the fertility-temperature problem.

Whether our findings extrapolate to other species, including mammals such as humans, is not yet clear. It’s certainly possible, given evidence across the animal kingdom that fertility is sensitive to heat stress.

Either way, unless global warming is radically curbed, animal fertility will likely decline. This means Earth may be heading for far more species extinctions than previously anticipated.



Read more:
The 1.5℃ global warming limit is not impossible – but without political action it soon will be


The Conversation

Belinda van Heerwaarden, Future Fellow, The University of Melbourne and Ary Hoffmann, Professor, School of BioSciences and Bio21 Institute, The University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

3 billion animals were in the bushfires’ path. Here’s what the royal commission said (and should’ve said) about them


Ashleigh Best, University of Melbourne; Christine Parker, University of Melbourne, and Lee Godden, University of Melbourne

The Black Summer bushfires were devastating for wildlife, with an estimated three billion wild animals killed, injured or displaced. This staggering figure does not include the tens of thousands of farm animals who also perished.

The bushfire royal commission’s final report, released on October 30, recognised the gravity of the fires’ extraordinary toll on animals.



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Click through the tragic stories of 119 species still struggling after Black Summer in this interactive (and how to help)

It recommended governments improve wildlife rescue arrangements, develop better systems for understanding biodiversity and clarify evacuation options for domestic animals.

While these changes are welcome and necessary, they’re not sufficient. Minimising such catastrophic impacts on wildlife and livestock also means reducing their exposure to these hazards in the first place. And unless we develop more proactive strategies to protect threatened species from disasters, they’ll only become more imperilled.

What the royal commission recommended

The royal commission recognised the need for wildlife rescuers to have swift and safe access to fire grounds.

In the immediate aftermath of the bushfires, some emergency services personnel were confused about the roles and responsibilities of wildlife rescuers. This caused delays in rescue operations.

To address this issue, the royal commission sensibly suggested all state and territory governments integrate wildlife rescue functions into their general disaster planning frameworks. This would improve coordination between different response agencies.



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The bushfire royal commission has made a clarion call for change. Now we need politics to follow

Another issue raised by the commission was that Australia does not have a comprehensive, central source of information about its native flora and fauna. This is, in part, because species listing processes are fragmented across different jurisdictions.

For example, a marsupial, the white-footed dunnart, is listed as vulnerable in NSW, but is not on the federal government’s list of threatened species.

To better manage and protect wild animals, governments need more complete information on, for example, their range and population, and how climate change threatens them.

As a result, the royal commission recommended governments collect and share more accurate information so disaster response and recovery efforts for wildlife could be more targeted, timely and effective.

A wildlife rescuer holds a koala with burnt feet in a burnt forest
Adelaide wildlife rescuer Simon Adamczyk takes a koala to safety on Kangaroo Island.
AAP Image/David Mariuz

Helping animals help themselves

While promising, the measures listed in the royal commission’s final report will only tweak a management system for wildlife already under stress. Current legal frameworks for protecting threatened species are reactive. By the time governments intervene, species have often already reached a turning point.

Governments must act to allow wild animals the best possible chances of escaping and recovering on their own.

This means prioritising the protection and restoration of habitat that allows animals to get to safety. As a World Wildlife Fund report explains, an animal’s ability to flee the fires and find safe, unburnt habitat — such as mesic (moist) refuges in gullies or near waterways — directly influenced their chances of survival.



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Summer bushfires: how are the plant and animal survivors 6 months on? We mapped their recovery

Wildlife corridors also assist wild animals to survive and recover from disasters. These connect areas of habitat, providing fast moving species with safe routes along which they can flee from hazards.

And these corridors help slow moving species, such as koalas, to move across affected landscapes after fires. This prevents them from becoming isolated, and enables access to food and water.

Hazard reduction activities, such as removing dry vegetation that fuels fires, were also a focus for the royal commission. These can coexist with habitat conservation when undertaken in ecologically-sensitive ways.

As the commission recognised, Indigenous land and fire management practices are informed by intimate knowledge of plants, animals and landscapes. These practices should be integrated into habitat protection policies in consultation with First Nations land managers.

The commission also suggested natural hazards, such as fire, be counted as a “key threatening process” under national environment law. But it should be further amended to protect vulnerable species under threat from future stressors, such as disasters.



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Governments also need to provide more funding to monitor compliance with this law. Another new World Wildlife Fund report warns that unless it is properly enforced, a further 37 million native animals could be displaced or killed as a result of habitat destruction this decade.

And, as we saw last summer, single bushfire events can push some populations much closer to extinction. For example, the fires destroyed a large portion of the already endangered glossy black-cockatoo’s remaining habitat.

What about pets and farm animals?

Pets and farm animals featured in the commission’s recommendations too.

During the bushfires, certain evacuation centres didn’t cater for these animals. This meant some evacuees chose not to use these facilities because they couldn’t take their animals with them.

To guide the community in future disasters, the commission said plans should clearly identify whether or not evacuation centres can accommodate people with animals.



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Seven ways to protect your pets in an emergency

Evacuation planning is crucial to effective disaster response. However, it is unfortunately not always feasible to move large groups of livestock off properties at short notice.

For this reason, governments should help landholders to mitigate the risks hazards pose to their herds and flocks. Researchers are already starting to do this by investigating the parts of properties that were burnt during the bushfires. This will help farmers identify the safest paddocks for their animals in future fire seasons.

Disasters are only expected to become more intense and extreme as the climate changes. And if we’re to give our pets, livestock and unique wildlife the best chance at surviving, it’s not enough only to have sound disaster response. Governments must preemptively address the underlying sources of animals’ vulnerability to hazards.



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How we plan for animals in emergencies


The Conversation

Ashleigh Best, PhD Candidate and Teaching Fellow, University of Melbourne; Christine Parker, Professor of Law, University of Melbourne, and Lee Godden, Director, Centre for Resources, Energy and Environmental Law, Melbourne Law School, University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

‘Compassionate conservation’: just because we love invasive animals, doesn’t mean we should protect them



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Kaya Klop-Toker, University of Newcastle; Alex Callen, University of Newcastle; Andrea Griffin, University of Newcastle; Matt Hayward, University of Newcastle, and Robert Scanlon, University of Newcastle

On an island off the Queensland coast, a battle is brewing over the fate of a small population of goats.

The battle positions the views of some conservation scientists and managers who believe native species must be protected from this invasive fauna, against those of community members who want to protect the goat herd to which they feel emotionally connected. Similar battles colour the management decisions around brumbies in Kosciuszko National Park and cats all over Australia.



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National parks are for native wildlife, not feral horses: federal court

These debates show the impact of a new movement called “compassionate conservation”. This movement aims to increase levels of compassion and empathy in the management process, finding conservation solutions that minimise harm to wildlife. Among their ideas, compassionate conservationists argue no animal should be killed in the name of conservation.

But preventing extinctions and protecting biodiversity is unlikely when emotion, rather than evidence, influence decisions. As our recent paper argues, the human experience of compassion and empathy is fraught with inherent biases. This makes these emotions a poor compass for deciding what conservation action is right or wrong.

It sounds good on paper

We are facing a biological crisis unparalleled in human history, with at least 25% of the world’s assessed species at risk of extinction. These trends are particularly bad in Australia, where we have one of the world’s worst extinction records and the world’s highest rate of mammal extinctions.

The federal government recently announced it will commit to a new ten-year threatened species strategy, focused on eradicating feral pests such as foxes and cats.



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One cat, one year, 110 native animals: lock up your pet, it’s a killing machine

This approach goes against the principles underpinning compassionate conservation. The movement, which first emerged in 2010, is founded on the ideals of “first do no harm” and “individuals matter”.

When you first think about it, this idea sounds great. Why kill some animals to save others?

Well, invasive animals — those either intentionally or accidentally moved to a new location — are one of the biggest threats to global biodiversity.

Invasive predators, such as cats and foxes, have caused the extinction of 142 vertebrate species worldwide. In Australia, feral and domestic cats kill more than 15 billion native animals per year.

Fortunately, endangered populations can recover when these pests are removed. Controlling pest numbers is one of the most effective tools available to conservationists.

Conflicting moral standpoints

Killing pests is at stark odds with the “do no harm” values promoted by the compassionate conservation movement.

Thousands of wild horses are rapidly degrading the ecosystems of Australia’s high country.

Compassionate conservationists argue it’s morally wrong to kill animals for management, whereas conservation scientists argue it’s morally wrong to allow species to go extinct — especially if human actions (such as the movement of species to new locations) threaten extinction.

These conflicting moral standpoints result in an emotional debate about when it is justified to kill or let be killed. This argument centres on emotion and moral beliefs. There is no clear right or wrong answer and, therefore, no resolution.

In an attempt to break this emotional stalemate, we explored the biases inherent in the emotions of compassion and empathy, and questioned if increased empathy and compassion are really what conservation needs.

Evolutionary biases

At first, compassion and empathy may appear vital to conservation, and on an individual level, they probably are. People choose to work in conservation because they care for wild species. But compassion and empathy come with strong evolutionary biases.

The first bias is that people feel more empathy toward the familiar — people care more for things they relate most closely to. The second bias is failure to scale-up — we don’t feel 100 times more sorrow when hearing about 100 people dying, compared to a single person (or species).

Evolution has shaped our emotions to peak for things we relate most strongly to, and to taper off when numbers get high — most likely to protect us from becoming emotionally overloaded.

Let’s put these emotions in the context of animal management. Decisions based on empathy and compassion will undoubtedly favour charismatic, relatable species over thousands of less-familiar small, imperilled creatures.

This bias is evident in the battle over feral horses in national parks. There is public backlash over the culling of brumbies, yet there is no such response to the removal of feral pigs, despite both species having similarly negative impacts on protected habitats.

More harm than good

If compassionate conservation is adopted, culling invasive species would cease, leading to the rapid extinction of more vulnerable native species. A contentious example is the race to save the endangered Tristan albatross from introduced mice on Gough Island in the south Atlantic.

Sealers introduced mice in the 1800s, and the mice have adapted to feed on albatross chicks, killing an estimated two million birds per year. Under compassionate conservation, lethal control of the mice would not be allowed, and the albatross would be added to the extinction list within 20 years.



Read more:
Invasive species are Australia’s number-one extinction threat

What’s more, compassionate conservation advocates for a more hands-off approach to remove any harm or stress to animals. This means even the management of threatened fauna would be restricted.

Under this idea, almost all current major conservation actions would not be allowed because of temporary stress placed on individual animals. This includes translocations (moving species to safer habitat), captive breeding, zoos, radio tracking and conservation fencing.

With 15% of the world’s threatened species protected in zoos and undergoing captive breeding, a world with compassionate conservation would be one with far fewer species, and we argue, much less conservation and compassion.

In this time of biodiversity crisis and potential ecosystem collapse, we cannot afford to let emotion bias our rationale. Yes, compassion and empathy should drive people to call for more action from their leaders to protect biodiversity. But what action needs to be taken should be left to science and not our emotions.



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Don’t blame cats for destroying wildlife – shaky logic is leading to moral panic


The Conversation

Kaya Klop-Toker, Conservation Biology Researcher, University of Newcastle; Alex Callen, Post-doctoral researcher, University of Newcastle; Andrea Griffin, Senior Lecturer, School of Psychology, University of Newcastle; Matt Hayward, Associate professor, University of Newcastle, and Robert Scanlon, PhD Candidate in Restoration Ecology, University of Newcastle

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bushfires left millions of animals dead. We should use them, not just bury them


Emma Spencer, University of Sydney; Chris Dickman, University of Sydney; Philip Barton, Australian National University, and Thomas Newsome, University of Sydney

Bushfires this season have left an estimated 1 billion dead animals in their wake, their carcasses dotting the blackened landscape.

Adding to the toll, farmers are being forced to euthanise injured and starving livestock and there are also calls to cull feral animals in fire-affected areas, including by aerial shooting.

The carcasses have already been flagged as a potential biosecurity threat, and the Australian Defence Force is tasked with collecting and burying the dead in mass graves.



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There’s logic in this. Carcasses can harbour nasty diseases such as botulism 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.

Carcasses provide important food sources to native animals, such as the lace goanna.

The Morrison Government has announced a A$50 million package to help wildlife and habitat recover from the fires, and yesterday met leading wildlife experts 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 – 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 goannas, wedge-tailed eagles and dingoes. 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 vulnerable prey.

Carcasses also feed insects such as flies, ants, beetles, and their larvae, and support important ecological processes such as 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 last for years.

Vegetation growth ‘halo’ around a kangaroo carcass. When animals die their nutrients can influence the landscape for years.

The negatives: spreading disease and sustaining feral animals

Carcasses are home to bacteria that help break down animal tissues. 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.



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Predators get the advantage when bushfires destroy vegetation

Leaving carcasses out in the open can also feed introduced predators such as feral cats and red foxes, putting small native animals at risk. Some weeds thrive in the nutrient-rich soils around carcasses too.

Introduced insects like the European wasp, which appeared en masse following fires in Kosciuszko National Park, also take advantage of carcass resources. These wasps are highly aggressive and attack and kill other native insects.

How long does a carcass stick around?

We know very little about the ecological role of carcasses in fire-affected areas, and it’s important that more research is carried out.

We know burnt animals can decompose faster 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.

Finding the right solution to a grisly problem

As climate change accelerates the number of natural disasters and 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’re left to rot. This happened for almost 100 feral horses 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’t the best option.



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Carcasses are more often buried following disease outbreaks or when livestock die. We saw this during the 2019 Queensland floods, 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.



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Composting kills most pathogens, whereas burial just moves the problem underground. It also suppresses smelly odours and doesn’t attract scavengers. The usable organic material resulting from the composting can also be applied to nutrient-poor soil.

Getting used to the ‘yuck’ factor of carcasses.

Composting can be time-consuming and hard to get right. It requires careful monitoring of temperature and moisture content to ensure all disease-causing pathogens are killed, and odours are suppressed.

There’s also a “yuck” factor and the public would probably need convincing for the method to be widely adopted.

But whatever option we choose, it’s clear there’s more we can do with carcasses than simply burying them.The Conversation

Emma Spencer, Ph.D. student, University of Sydney; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; Philip Barton, Honorary Senior Lecturer, Fenner School of Environment and Society, Australian National University, and Thomas Newsome, Lecturer, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How Australia made poisoning animals normal



File 20190214 1721 6igdy2.jpg?ixlib=rb 1.1
Colonial graziers found it more effective to poison dingoes than rely on convict shepherds to protect their flocks.
Justine Philip/AMMRIC 2017, Author provided

Justine M. Philip, University of New England

One of the many difficulties faced by the pioneers of Australia’s sheep industry was finding a reliable shepherd. Among the convict labour available, for every two experienced farm labourers there were five convicted sheep, horse, cattle or poultry thieves.

The conditions were demanding. Convicts returning from pasture with fewer sheep than they left with faced a penalty of up to 100 lashes – close to a death sentence. Going bush was the only option for those unwilling to submit to the punishment back “inside”, as the settlements were called. Sheep were lost through negligence and misadventure, others to hungry dingoes.



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Eradicating dingoes therefore had a double benefit for the graziers: they would reduce stock losses, and eliminate the need for (unreliable) convict labour.

Reverend Samuel Marsden announced the first plan for the destruction of the native dog in Sydney Town, 1811. On offer was a generous bounty of one gallon of spirits for each complete skin of a fully grown native dog.

(Incidentally, Marsden went on to introduce sheep to New Zealand, followed by the mysterious disappearance of the Maori kuri dog in following decades.)

Three years later, the first instance of using poison to eradicate the dingo was recorded in the Sydney Gazette. A “gentleman farmer” with extensive stock in the Nepean District initiated the operation. By applying arsenic to the body of a dead ox on his property, he managed to eradicate all the wild dogs from his landholding. The technique gathered a quiet following, though there were concerns that in the wrong hands this venture could inadvertently backfire on the penal colony.

Revolutionising toxicology

In 1818 French scientist Pierre Joseph Pelletier successfully extracted beautiful but sinister crystals from the plant nux vomica. This discovery revolutionised toxicology: it enabled mass production of a highly toxic, stable and cheap poison known as strychnine.

Strychnos Nux vomica, Köhler’s Medizinal-Pflanzen 1887 (Plate 107).

The crystals were soon to be exported en masse around the world. Strychinine became an essential item in the Australian farmer’s toolkit, and by 1852 its use on landholdings was mandatory to control unwanted wildlife. In 1871 author Anthony Trollope wrote in his observations of Australian life:

On many large runs, carts are continually being taken round with (strychnine) baits to be set on the paths of the dingo. In smaller establishments the squatter or his head-man goes about with strychnine in his pocket and lumps of meat tied up in a handkerchief.

Over the course of the 19th century, the Australian economy became irreversibly dependent on this industrial agrochemical farming system.

The pace of Australia’s agricultural revolution was rapid; between 1822, when fine wool became NSW’s major export product, and 1850, the national flock numbers increased from 120,000 to 16 million. By 1892 the Australian sheep flock numbered 106 million.

Fluctuations in the size of the Australian sheep flock 1800-2017.
Australian Bureau of Statistics

A central Australian dingo extermination campaign was launched in 1897, to eradicate dingo and rabbit populations from South Australia’s arid zone. Described as the “Party of Poisoners”, the team travelled from Gawler Range to Wilpena Pound, covering an area 1,000km long by 480km wide. It took five months.



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The poisoners dispensed phosphorised pollard and strychnine sticks and laid poisoned grain in lightly covered furrows. Meat baits were placed around the bases of the red and white mallee bush. Billabongs were poisoned. All species that might have competed for the scarce resources were effectively eliminated – carnivore and herbivore. Farming ultimately failed in the region. The natural biodiversity never recovered.

The Hudson Bros. Poison Cart 1883: initially designed to dispense dingo baits, by 1920 the.
devices were being used in the thousands, to eradicate herbivores.
Powerhouse Museum

The legacy of Australia’s chemical-dependent farming over the past 200 years remains largely unacknowledged in conversations about the current biodiversity crisis. Australia has around 500 threatened animal species, and our rate of mammalian extinctions is unparalleled anywhere in the world. The main drivers of the crisis are attributed to introduced species, changed fire regimes, and land clearing.

In the history of agricultural expansion, it was the dingo that was the initial target of eradication campaigns. Land clearing worked in concert with the broad scale application of vertebrate pesticides. The expansion in the application, range, methods of delivery and quantity of poison and poisoned baits applied was rapid, using increasingly sophisticated machinery.

The effects reverberated throughout Australia’s ecosystems: the removal of the dingo, the top order predator, lead to the explosion of herbivore populations, more poisons, the establishment of introduced species and destabilising of the native ecosystem.

Influence of the dingo on ecosystem function.
Restoration Ecology, Newsome et al. 2015

In the 1870s newspapers were reporting on the impact of herbivore populations including the introduced rabbit. The South Australian Advertiser, wrote in 1877:

We have destroyed the balance of nature in two ways simultaneously, by destroying the carnivore and introducing a new herbivorous animal of immense reproductive powers.



Read more:
Was agriculture the greatest blunder in human history?

In the 21st century, more vertebrate poisons are dispensed by air in National Parks, than on private land – in efforts to protect biodiversity from invasive species.

My research examines how poison has been normalised in land management. The use of vertebrate pesticides has been supported by services and systems embedded within Australia’s social, political and legal framework for 200 years.

Applying more vertebrate pesticides to the environment to try and solve the problem, is arguably an extreme case of mistaking the poison for the cure.The Conversation

Justine M. Philip, Doctor of Philosophy, Ecosystem Management, University of New England

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Comic explainer: forest giants house thousands of animals (so why do we keep cutting them down?)



File 20181129 170241 np8k0s.png?ixlib=rb 1.1

Wes Mountain/The Conversation, CC BY-ND

Madeleine De Gabriele, The Conversation and Wes Mountain, The Conversation

Giant eucalypts play an irreplaceable part in many of Australia’s ecosystems. These towering elders develop hollows, which make them nature’s high-rises, housing everything from endangered squirrel-gliders to lace monitors. Over 300 species of vertebrates in Australia depend on hollows in large old trees.

These “skyscraper trees” can take more than 190 years to grow big enough to play this nesting and denning role, yet developers are cutting them down at an astounding speed. In other places, such as Victoria’s Central Highlands Mountain Ash forests, the history of logging and fire mean that less than 1.2% of the original old-growth forest remains (that supports the highest density of large old hollow trees). And it’s not much better in other parts of our country.

David Lindenmayer explains how these trees form, the role they play – and how very hard they are to replace.



Read more:
Mountain ash has a regal presence: the tallest flowering plant in the world


Wes Mountain/The Conversation, CC BY-ND



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The plan to protect wildlife displaced by the Hume Highway has failed

Sign up to Beating Around the Bush, a series that profiles native plants: part gardening column, part dispatches from country, entirely Australian.The Conversation

Madeleine De Gabriele, Deputy Editor: Energy + Environment, The Conversation and Wes Mountain, Multimedia Editor, The Conversation

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Why we shouldn’t be too quick to blame migratory animals for global disease


Alice Risely, Deakin University; Bethany J Hoye, University of Wollongong, and Marcel Klaassen, Deakin University

Have you ever got on a flight and the person next to you started sneezing? With 37 million scheduled flights transporting people around the world each year, you might think that the viruses and other germs carried by travellers would be getting a free ride to new pastures, infecting people as they go.

Yet pathogenic microbes are surprisingly bad at expanding their range by hitching rides on planes. Microbes find it difficult to thrive when taken out of their ecological comfort zone; Bali might just be a tad too hot for a Tasmanian parasite to handle.

But humans aren’t the only species to go global with their parasites. Billions of animals have been flying, swimming and running around the globe every year on their seasonal migrations, long before the age of the aeroplane. The question is, are they picking up new pathogens on their journeys? And if they are, are they transporting them across the world?

Read more: A tale of three mosquitoes: how a warming world could spread disease

Migratory animals are the usual suspects for disease spread

With the rate of zoonotic diseases (pathogens that jump from animals to humans) on the rise, migratory animals have been under increasing suspicion of aiding the spread of devastating diseases such as bird flu, Lyme disease, and even Ebola.

These suspicions are bad for migrating animals, because they are often killed in large numbers when considered a disease threat. They are also bad for humans, because blaming animals may obscure other important factors in disease spread, such as animal trade. So what’s going on?

Despite the logical link between animal migration and the spread of their pathogens, there is in fact surprisingly little direct evidence that migrants frequently spread pathogens long distances.

This is because migratory animals are notoriously hard for scientists to track. Their movements make them difficult to test for infections over the vast areas that they occupy.

But other theories exist that explain the lack of direct evidence for migrants spreading pathogens. One is that, unlike humans who just have to jump on a plane, migratory animals must work exceptionally hard to travel. Flying from Australia to Siberia is no easy feat for a tiny migratory bird, nor is swimming between the poles for giant whales. Human athletes are less likely to finish a race if battling infections, and likewise, migrant animals may have to be at the peak of health if they are to survive such gruelling journeys. Sick travellers may succumb to infection before they, or their parasitic hitchhikers, reach their final destination.

Put simply, if a sick animal can’t migrate, then neither can its parasites.

On the other hand, migrants have been doing this for millennia. It is possible they have adapted to such challenges, keeping pace in the evolutionary arms race against pathogens and able to migrate even while infected. In this case, pathogens may be more successful at spreading around the world on the backs of their hosts. But which theory does the evidence support?

Sick animals can still spread disease

To try and get to the bottom of this question, we identified as many studies testing this hypothesis as we could, extracted their data, and combined them to look for any overarching patterns.

We found that infected migrants across species definitely felt the cost of being sick: they tended to be in poorer condition, didn’t travel as far, migrated later, and had lower chances of survival. However, infection affected these traits differently. Movement was hit hardest by infection, but survival was only weakly impacted. Infected migrants may not die as they migrate, but perhaps they restrict long-distance movements to save energy.

So pathogens seem to pose some costs on their migratory hosts, which would reduce the chances of migrants spreading pathogens, but perhaps not enough of a cost to eliminate the risk completely.

Read more: Giant marsupials once migrated across an Australian Ice Age landscape

But an important piece of the puzzle is still missing. In humans, travelling increases our risk of getting ill because we come into contact with new germs that our immune system has never encountered before. Are migrants also more susceptible to unfamiliar microbes as they travel to new locations, or have they adapted to this as well?

Guts of migrants resistant to microbial invasion

To investigate the susceptibility of migrants, we went in a different direction and decided to look at the gut bacteria of migratory shorebirds – grey, unassuming birds that forage on beaches or near water, and that undergo some of the longest and fastest migrations in the animal kingdom.

Most animals have hundreds of bacterial species living in their guts, which help break down nutrients and fight off potential pathogens. Every new microbe you ingest can only colonise your gut if the environmental conditions are to its liking, and competition with current residents isn’t too high. In some cases, it may thrive so much it becomes an infection.

The Red-necked stint is highly exposed to sediment microbes as it forages for the microscopic invertebrates that fuel its vast migrations.
Author provided

We found the migratory shorebirds we studied were exceptionally good at resisting invasion from ingested microbes, even after flying thousands of kilometres and putting their gut under extreme physiological strain. Birds that had just returned from migration (during which they stopped in many places in China, Japan, and South East Asia), didn’t carry any more species of bacteria than those that had stayed around the same location for a year.

The ConversationAlthough these results need to be tested in other migratory species, our research suggests that, like human air traffic, pathogens might not get such an easy ride on their migratory hosts as we might assume. There is no doubt that migrants are involved in pathogen dispersal to some degree, but there is increasing evidence that we shouldn’t jump the gun when it comes to blaming migrants.

Alice Risely, PhD candidate in Ecology, Deakin University; Bethany J Hoye, Lecturer in Animal Ecology, University of Wollongong, and Marcel Klaassen, Alfred Deakin Professor and Chair in Ecology, Deakin University

This article was originally published on The Conversation. Read the original article.