Invasive species are Australia’s number-one extinction threat



Barking Owls are one of Australia’s 1,770 threatened or endangered species.
Navin/Flickr, CC BY-SA

Andy Sheppard, CSIRO and Linda Broadhurst, CSIRO

This week many people across the world stopped and stared as extreme headlines announced that one eighth of the world’s species – more than a million – are threatened with extinction.

According to the UN report from the Intergovernmental Science-Policy Platform for Biodiversity and Ecosystem Services (IPBES) which brought this situation to public attention, this startling number is a consequence of five direct causes: changes in land and sea use; direct exploitation of organisms; climate change; pollution; and invasion of alien species.




Read more:
‘Revolutionary change’ needed to stop unprecedented global extinction crisis


It’s the last, invasive species, that threatens Australian animals and plants more than any other single factor.

Australia’s number one threat

Australia has an estimated 600,000 species of flora and fauna. Of these, about 100 are known to have gone extinct in the last 200 years. Currently, more than 1,770 are listed as threatened or endangered.

While the IPBES report ranks invasive alien species as the fifth most significant cause of global decline, in Australia it is a very different story.

Australia has the highest rate of vertebrate mammal extinction in the world, and invasive species are our number one threat.

Cats and foxes have driven 22 native mammals to extinction across central Australia and a new wave of decline – largely from cats – is taking place across northern Australia. Research has estimated 270 more threatened and endangered vertebrates are being affected by invasive species.

Introduced vertebrates have also driven several bird species on Norfolk Island extinct.

The effects of invasive species are getting worse

Although Australia’s stringent biosecurity measures have dramatically slowed the number of new invasive species arriving, those already here have continued to spread and their cumulative effect is growing.

Recent research highlights that 1,257 of Australia’s threatened and endangered species are directly affected by 207 invasive plants, 57 animals and three pathogens.

These affect our unique biodiversity, as well as the clean water and oxygen we breath – not to mention our cultural values.

When it comes to biodiversity, Australia is globally quite distinct. More than 70% of our species (69% of mammals, 46% of birds and 93% of reptiles) are found nowhere else on earth. A loss to Australia is therefore a loss to the world.

Some of these are ancient species like the Wollemi Pine, may have inhabited Australia for up to 200 million years, well before the dinosaurs.




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But invasive species are found in almost every part of Australia, from our rainforests, to our deserts, our farms, to our cities, our national parks and our rivers.

The cost to Australia

The cost of invasive species in Australia continue to grow with every new assessment.

The most recent estimates found the cost of controlling invasive species and economic losses to farmers in 2011-12 was A$13.6 billion. However this doesn’t include harm to biodiversity and the essential role native species play in our ecosystems, which – based on the conclusions of the IPBES report – is likely to cost at least as much, and probably far more.

Rabbits, goats and camels prevent native desert plant community regeneration; rabbits alone impacting over 100 threatened species. Rye grass on its own costs cereal farmers A$93M a year.

Aquaculture diseases have affected oysters and cost the prawn industry $43M.

From island to savannah

Globally, invasive species have a disproportionately higher effect on offshore islands – and in Australia we have more than 8,000 of these. One of the most notable cases is the case of the yellow crazy ants, which killed 15,000,000 red land crabs on Christmas Island.




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Nor are our deserts immune. Most native vertebrate extinctions caused by cats have occurred in our dry inland deserts and savannas, while exotic buffel and gamba grass are creating permanent transformation through changing fire regimes.

Australia’s forests, particularly rainforests, are also under siege on a number of fronts. The battle continues to contain Miconia weed in Australia – the same weed responsible for taking over 70% of Tahiti’s native forests. Chytrid fungus, thought to be present in Australia since 1970, has caused the extinction of at least four frog species and dramatic decline of at least ten others in our sensitive rainforest ecosystems.

Myrtle rust is pushing already threatened native Australian Myrtaceae closer to extinction, notably Gossia gonoclada, and Rhodamnia angustifolia and changing species composition of rainforest understories, and Richmond birdwing butterfly numbers are under threat from an invasive flower known as the Dutchman’s pipe.

Australia’s rivers and lakes are also under increasing domination from invasive species. Some 90% of fish biomass in the Murray Darling Basin are European carp, and tilapia are invading many far north Queensland river systems pushing out native species .

Invasive alien species are not only a serious threat to biodiversity and the economy, but also to human health. The Aedes aegypti mosquito found in parts of Queensland is capable of spreading infectious disease such as dengue, zika, chikungunya and yellow fever.

And it’s not just Queensland that is under threat from diseases spread by invasive mosquitoes, with many researchers and authorities planning for when, not if, the disease carrying Aedes albopictus establishes itself in cooler and southern parts of Australia.




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What solutions do we have?

Despite this grim inventory, it’s not all bad news. Australia actually has a long history of effectively managing invasive species.

Targeting viruses as options for controlling rabbits, carp and tilapia; we have successfully suppressed rabbit populations by 70% in this way for 50 years.

Weeds too are successful targets for weed biological control, with over a 65% success rate controlling more than 25 targets.

The IPBES report calls for “transformative action”. Here too Australia is at the forefront, looking into the potential of gene-technologies to suppress pet hates such as cane toads.




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We’ve cracked the cane toad genome, and that could help put the brakes on its invasion


Past and current invasive species programs have been supported by governments and industry. This has provided the type of investment we need for long-term solutions and effective policies.

Australia is better placed now, with effective biosecurity policies and strong biosecurity investment, than many countries. We will continue the battle against invasive species to stem biodiversity and ecosystem loss.The Conversation

Andy Sheppard, Research Director CSIRO Health & Biosecurity, CSIRO and Linda Broadhurst, Director, Centre for Australian National Biodiversity Research, CSIRO

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

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Like cats and dogs: dingoes can keep feral cats in check



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Feral cats are linked to the extinction of at least 20 Australian mammals.
Shutterstock

Mike Letnic, UNSW and Ben Feit

The role of dingoes in the Australian landscape is highly debated between ecologists, conservationists and graziers. They kill livestock, but also hunt introduced animals and keep kangaroo populations in check.

Now new research sheds more light on the benefits dingoes bring to the outback. For the first time, our research clearly shows that dingoes suppress feral cat numbers.

Our research, published recently in Ecosystems, used the world’s largest fence to compare essentially identical environments with and without dingoes. Over the course of the six-year study, dingoes drove down cat numbers – and kept them down.




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Feral cats are out of control

Feral cats are a serious conservation threat. They have been linked to the extinction of at least 20 mammal species in Australia and threaten the ongoing survival of more than 100 native species.

For our study, we asked whether “top-down” pressure from dingoes (through direct killing and competition for food) had a greater influence on controlling cat numbers than “bottom-up” effects (the availability of shared food sources preyed on by cats).

Dingoes drive down the population of introduced animals.
Kim/flickr, CC BY-SA

We conducted our study by comparing the numbers of dingoes, cats and their major prey species on either side of the dingo fence in the Strzelecki Desert. The fence runs along the borders of New South Wales and South Australia and was originally built to exclude dingoes from sheep grazing lands in NSW.

The state border follows the longitude line 141 east, so the fence does not demarcate any natural boundary. It simply cuts a straight line through sand dunes with similar landforms and vegetation on either side. Thus the dingo fence provides a unique opportunity to study apex predators’ effects on ecosystems: dingoes are common on the SA side, “outside” the fence, whereas on the NSW “inside” of the fence, dingoes are rare due to intensive persecution by humans.




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Let’s move the world’s longest fence to settle the dingo debate


We collected data from sites on either side of the fence in the Strzelecki Desert, at roughly four-month intervals between 2011 and 2017. Dingo and cat scat was collected at each site, to analyse and compare diets, and spotlight searches were used to record numbers of dingoes, feral cats, as well as two of their common shared food sources: rabbits and hopping mice.

Spotlight surveys revealed dingoes to be virtually absent from study areas inside the fence, with only four dingoes recorded during the study. Where dingoes were rare inside the fence, cat numbers closely followed fluctuations of their prey species consistently over the six-year span of our study. As prey numbers increased, cat numbers also increased, and similarly as prey numbers declined, cat numbers also declined.

A feral cat in outback Australia.
Shutterstock

Outside the fence, where dingoes were common, it was quite a different story. There, cat numbers were consistently lower, with numbers of both cats and dingoes following fluctuations in prey numbers across the first two years of the study. However, from 2013 onward, dingo numbers remained high and matched trends in their prey numbers for the remainder of the study.

During this time, cat numbers remained low, and by the end of 2015, cats had virtually disappeared from our study sites outside the fence and were not recorded during spotlight surveys between November 2015 and the end of our study in July 2017.

The most likely explanation for this drastic reduction in cat populations is through interference competition – either by dingoes killing some cats or by scaring others away from habitats in which they would usually hunt. Indeed, we occasionally found cat remains in dingo scats, which suggests dingoes prey on cats.

Although our scat analyses indicated that dingoes and cats eat similar foods, there was no evidence that competition for food was a major factor in how dingoes reduce cat populations. This is because prey were plentiful outside the fence, where dingoes were common and cats were rare.




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This research show how dingoes can help conservation efforts by suppressing feral cat populations. It adds to previous work showing dingoes are important in maintaining healthy ecosystems, as they reduce and eradicate feral herbivores like pigs and goats, and stop kangaroos from overpopulating districts.


This article was updated on April 5 to credit Ben Feit as a co-author.The Conversation

Mike Letnic, Professor, Centre for Ecosystem Science, UNSW and Ben Feit, Post-doctoral researcher

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

Invasive ants: federal budget takes aim but will it be a lethal shot?



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Argentine ants are a fact of life in many parts of Australia, but can still potentially be banished from Norfolk Island.
Davefoc/Wikimedia Commons, CC BY-SA

Lori Lach, James Cook University

Amid all the usual items we expect to see in the federal budget was one that raised eyebrows: A$28.8 million for three ant eradication programs.

Yet amid the inevitable media puns about the government “upping the ant-e”, we should note that these funds are for the continuation of existing programs that have already attracted significant funding and made substantial progress. Stopping now would have meant previous funding was wasted.

The funds will go a long way towards protecting Australia’s economy and environment from the damage wrought by invasive ants. But despite the apparent cash splurge, it nevertheless falls short of what is really needed.

Of the $28.8 million, $18.3 million was for the National Red Imported Fire Ant Eradication Program. These funds are part of a $411 million, ten-year program begun in 2017 to eradicate red imported fire ants from southeast Queensland, the only place they are found in Australia.




Read more:
Cannibalism helps fire ants invade new territory


Removing these pests will avoid an estimated $1.65 billion in total costs to 19 different parts of the economy. With previous funding, the program eradicated these ants from 8,300 hectares near the Port of Brisbane, making it the world’s largest ant eradication to date.

The Yellow Crazy Ant Eradication Program was allocated $9.2 million over three years. Yellow crazy ants have caused a cascade of ecological effects on Christmas Island, and at their peak abundance temporarily blinded a Queensland cane farmer with their acid spray.

The Wet Tropics Management Authority, which runs the program, had requested $6 million per year for six years to continue removing the ant from in and around the Wet Tropics World Heritage Area. The federal funding is $3 million short of this, and the authority is still waiting to hear whether the Queensland government will provide the remainder.

Since 2013, the program has received $9.5 million from the federal government (and $3 million from the Queensland government). No yellow crazy ants have been observed in about half of the target area in more than a year. A yet-to-be published analysis estimates the benefit-cost ratio for the program as 178:1.

“It’s a mop-up operation… we’ve got our foot on the throat of this thing.”

A further $1.3 million was allocated to the Argentine Ant Eradication Strategy on Norfolk Island in the South Pacific. Argentine ants have invaded places with Mediterranean-type climates all over the world, including southwestern Western Australia and parts of southern Australia, and become firmly established. But unlike those areas, the population on Norfolk Island is still considered small enough to be eradicable, and federally funded efforts to remove them began in 2010.

Yellow crazy ants in Queensland and Argentine ants on Norfolk Island directly threaten World Heritage Areas. The ants can have significant impacts on native birds, mammals, insects, reptiles, amphibians, and plants. Getting rid of them is important for meeting Australia’s international obligations to protect World Heritage sites.

What is ant eradication?

Ant eradication means removing all individuals of a particular ant species from a given area.

The first step is to define the extent of that area. Depending on the species, this may involve visual searches and/or placing lures such as sausages, cat food, or jam to attract the ants. The public can help by notifying relevant authorities of unusual ants in their gardens, and by not transporting materials that have ants on them.

The second step is treatment. Currently, the only way to eradicate ants is with insecticidal baits. Ants’ social structure makes this particularly challenging: killing the queens is vital for eradication, but queens typically stay sheltered in the nest – the only ants we see out foraging are workers.

Some of the most problematic ant species can have hundreds of queens and tens of thousands of workers per nest. They can reach extraordinarily high densities, partly because invasive ant species, unlike most of our native ant species, do not fight one another for territories.

Yellow crazy ants, proving it is possible to feel sorry for a cockroach.
Bradley Rentz/Wikimedia Commons, CC BY-SA

Beating ants means turning their biology against them. Bait needs to be attractive enough for workers to bring back to the colony and share, but not so deadly that they die before they get there. (And yes, this means if you’re spraying foraging ants in your kitchen you won’t get rid them for good, because the queens are somewhere hidden, laying more eggs and making more ants.)

Most ant eradication programs take three to four years to fine-tune their baiting regime because of a multitude of factors that need to be considered, such as seasonal changes in ant foraging behaviour and food preference, and the desire to avoid harming non-target species. Typically, two to six treatments are required, depending on the ant species, the size of the area, and the habitat type.

Beating the 1%

The hardest part of ant eradication is the end-game. Getting rid of the final 1% requires first finding them. This may mean painstaking searches through hundreds of hectares of bushland and residential areas, and the placement of hundreds of thousands of lures. Detector dogs can be very helpful, but they cannot be used in all environments and also need substantial resources for training, handling, and maintenance.

Ironically, it is at this stage that public and political support for eradication programs is most likely to wane, because ant numbers are too low to be seen as a threat to the public, economy or environment. Yet it is vital not to stop now, or else the remaining 1% will simply build up their numbers again. Experienced staff are also lost when programs suffer cuts or delays in their funding.




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Eradicating fire ants is still possible, but we have to choose now


Disappointingly not mentioned in the budget was funding for eradicating electric ants. Like red imported fire ants, electric ants have a painful sting, and when left to multiply will eventually turn gardens and swimming pools into no-go zones. They also pose a significant threat to native animals such as the southern cassowary, and can blind animals as large as elephants.

They are currently only found in the Cairns region. The National Electric Ant Eradication Program, funded by federal and state governments, ran from 2006 until 2017 and had likely reduced numbers down to that last 1%. The program has been running on state funding with reduced staff since then, but several new detections in the past three months demonstrate the cost of the gap in funding.

In those inevitable “federal budget winners and losers” lists, invasive ants have found themselves firmly in the losers column for 2019. But it’s worth remembering that most of the world’s roughly 15,000 known ant species provide vital services for the functioning of our ecosystems.

They aerate soil and redistribute its nutrients, protect plants from herbivores, disperse seeds, and repurpose dead organisms. They may even help slow down the spread of those pesky invasive ants that are much less friendly.The Conversation

Lori Lach, Associate Professor, James Cook University

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

Cannibalism helps fire ants invade new territory



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Fire ant stings can be deadly to people who have an allergic reaction to their venom.
Forest and Kim Starr/Flickr, CC BY-SA

Pauline Lenancker, James Cook University and Lori Lach, James Cook University

Tropical fire ants (Solenopsis geminata), originally from central and South America, are a highly aggressive, invasive ecological pest. Our new research has shed light on how they successfully establish new colonies.

An allergic reaction to painful tropical fire ant bites.
Pauline Lenancker, Author provided

While we don’t know exactly how widespread tropical fire ants are in Australia, they are well established around Darwin and Katherine, as well as on Christmas Island and Ashmore Reef. Disturbing one of their nests will result in many workers inflicting painful stings on the intruder, and can trigger an allergic reaction in some people.

When invasive ants move to a new region, the pioneers may be one or a few colonies. Because these pioneers are isolated, they often inbreed, which causes genetic problems in their offspring. But our new research, published in Scientific Reports, reveals how tropical fire ants use cannibalism to survive and spread, despite their low genetic diversity.




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Eradicating fire ants is still possible, but we have to choose now


Sons and daughters

Founding new colonies is how fire ants spread. Queens fly off to start their own colonies just after they have mated. It is a perilous journey – they need to avoid predators and find a good spot to start laying eggs. If queens do not quickly rear daughters that can forage, called workers, they will starve to death.

Queens can lay two different types of eggs: fertilised eggs, which will develop into workers, and unfertilised eggs, which will develop into males. Therefore, female workers have two copies of each gene (diploid), while males have a single copy of each gene (haploid). However, when an ant queen and her mate are closely related, a flaw in the sex determination system of ants causes half of the fertilised eggs to develop into diploid males instead of workers.

The role of males is only to mate with queens – they do not forage, and they die after they have mated. Queens founding a colony have no interest in producing males, because males will not feed them. What’s more, diploid males are often sterile, and their larvae are larger than worker larvae. Therefore, queens can waste precious resources feeding fat useless sons instead of workers.

We wanted to find out how common diploid males are in field colonies, and how queens could successfully start colonies despite them. Understanding how tropical fire ants spread, we hope, can help us stop them expanding their range.

Abandoned and eaten

Our field sampling of tropical fire ant colonies around Darwin revealed eight out of ten colonies produced diploid males.

We collected 1,187 queens that had just mated, and assigned them to start colonies on their own or with other queens.

We observed that in 34% of colonies producing diploid males, diploid male larvae were placed in the colony trash pile by the queens instead of being kept with the worker larvae. It is usual for ants to keep dead individuals away from the rest of the colony, but when we looked at some of these abandoned larvae under a microscope, we realised they were still alive.




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Queens not only abandoned their sterile sons, they ate them. Three-quarters of the 109 sterile male larvae disappeared from the colonies within 12 days of when we first observed them. Because the queens were the only adult ants present in the colony, this means the queens were eating their diploid males or feeding them to their worker larvae.

This cannibalistic behaviour allowed the queens to redirect nutrients towards themselves or productive members of their colony. Diploid male larvae require more food than worker larvae to develop, so we expected queens from diploid male producing colonies to lose more weight than queens from colonies that only produced workers, but we found that was not the case. Queens with diploid males lost less weight or as much weight as queens from regular colonies, probably because they ate their sterile sons.

We also found queens who worked together in groups to start a colony reared more workers. Therefore, queens in groups would likely have a better chance of survival even if they produced sterile males. But in 6% of colonies, queens did not tolerate having housemates and dismembered other queens.

A queen dismembered by a tetchy rival.
Pauline Lenancker, Author provided

For tropical fire ants, cannibalising sterile sons and cooperative brood rearing among queens are two behavioural mechanisms for avoiding inbreeding costs. A third possible mechanism for the queens is to “sleep around”.

Promiscuity would increase the chance of mating with a genetically different male, and reduce the likelihood of producing diploid sons.

Queens only mate right before starting their colony and store the sperm in an organ called the spermatheca. We genetically analysed sperm from the spermatheca of 40 queens, but found no evidence queens had mated with more than one male.

Tropical fire ants are currently established on Ashmore Reef, a protected Australian Marine Park which is an important breeding site for seabirds and turtles. The invasive ant threatens this sanctuary by attacking seabird and turtle hatchlings. Accidental spreading of tropical fire ants to suitable habitats in the Northern Territory, Queensland and Western Australia would threaten invaluable ecosystems as well as our health and lifestyles.




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How we wiped out the invasive African big-headed ant from Lord Howe Island


The current eradication program for the closely related red imported fire ant (Solenopsis invicta) in Queensland has been granted A$411 million over ten years, and failure to eradicate red imported fire ants could cost Australia A$1.65 billion per year in damaged crops, livestock harmed and people treated. The more we learn about invasive ant biology, the closer we are to new methods of preventing their spread.The Conversation

Pauline Lenancker, PhD student in biology and ecology, James Cook University and Lori Lach, Associate Professor, James Cook University

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

The summer bushfires you didn’t hear about, and the invasive species fuelling them



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Fire has burned through a swathe of the Tjoritja National Park.
Author provided

Christine Schlesinger, Charles Darwin University and Barry Judd, Charles Darwin University

In January 2019, fires burned across a 100-kilometre length of the iconic Tjoritja National Park in the West MacDonnell Ranges, from Ormiston Gorge nearly to the edge of Alice Springs.

These fires affected an area comparable to the recent Tasmanian fires, but attracted relatively little national attention. This is partly because the fires in Tasmania were so unusual – but we believe the fires in central Australia were just as unexpected.




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Dry lightning has set Tasmania ablaze, and climate change makes it more likely to happen again


In the past, fires of this magnitude have tended to come after heavy rain that powers the growth of native grasses, providing fuel for intense and widespread fires. But our research highlights the new danger posed by buffel grass, a highly invasive foreigner sweeping across inland Australia and able to grow fast without much water.

Far from being pristine, Tjoritja and the Western MacDonnell Ranges are now an invaded landscape under serious threat. Our changing climate and this tenacious invader have transformed fire risk in central Australia, meaning once-rare fires may occur far more often.

Buffel grass in Australia

Buffel grass is tough and fast-growing. First introduced to Australia in the 1870s by Afghan cameleers, the grass was extensively planted in central Australia in the 1960s during a prolonged drought.

Introductions of the drought-resistant plant for cattle feed and dust suppression have continued, and in recent decades buffel grass has become a ubiquitous feature of central Australian landscapes, including Tjoritja.

Buffel grass has now invaded extensive areas in the Northern Territory, Queensland, Western Australia and South Australia and is spreading into New South Wales and Victoria. It was legally recognised as a key threat in 2014, but so far only South Australia has prohibited its sale and created statewide zoning to enforce control or destruction.

Buffel grass crowds out other plants, creating effective “monocultures” – landscapes dominated by a single species. In central Australia, where Aboriginal groups retain direct, active and enduring links to Country, buffel grass makes it hard or impossible to carry out important cultural activities like hunt game species, harvest native plant materials or visit significant sites.

Buffel grass impacts on Anangu Pitjantjatjara Yankunytjatjara communities in central Australia.

But buffel grass isn’t only a threat to biodiversity and Indigenous cultural practices. In January the Tjoritja fires spread along dry river beds choked with buffel, incinerating many large old-growth trees. Much like the alpine forests of Tasmania, the flora of inland river systems has not adapted to frequent and intense fires.

We believe the ability of the fires to spread through these systems, and their increased intensity and size, can be directly attributed to buffel grass.

Fire and buffel grass

Because of the low average rainfall, widespread fires in central Australia have been rare in the recorded past, only following unusual and exceptionally high rainfall.

This extreme rain promoted significant growth of native grasses, which then provided fuel for large fires. There could be decades between these flood and fire cycles. However, since the Tjoritja (previously West MacDonnell Ranges) National Park was established in the 1990s, there have been three large-scale fires in 2001, 2011 and 2019.

What has changed? The 2001-02 and 2011-12 fires both came after heavy rainfall years. In fact, 2011 saw one of the biggest La Niña events on record.

Climate change predictions suggest that central Australia will experience longer and more frequent heatwaves. And although total annual rainfall may stay the same, it’s predicted to fall in fewer days. In other words, we’ll see heavy storms and rainfall followed by long heatwaves: perfect conditions for grass to grow and then dry, creating abundant fuel for intense fires.

The remains of a corkwood tree after an unplanned bushfire in an area heavily invaded by buffel grass near Simpsons Gap. Very few large old corkwood trees now remain in this area.
Author provided

If central Australia, and Tjoritja National Park in particular, were still dominated by a wide variety of native grasses and plants, this might not be such a problem. But buffel grass was introduced because it grows quickly, even without heavy rain.

The fires this year were extraordinary because there was no unusually high rainfall in the preceding months. They are a portent of the new future of fire in these ecosystems, as native desert plant communities are being transformed into dense near-monocultures of introduced grass.

The fuel that buffel grass creates is far more than native plant communities, and after the fire buffel grass can regenerate more quickly than many native species.

So we now have a situation in which fuel loads can accumulate over much shorter times. This makes the risk of fire in invaded areas so high that bushfire might now be considered a perpetual threat.

Changing fire threat

In spinifex grasslands, traditional Aboriginal burning regimes have been used for millennia to renew the landscape and promote growth while effectively breaking up the landscape so old growth areas are protected and large fires are prevented. Current fire management within Tjoritja “combines traditional and scientific practices”.

However, these fire management regimes do not easily translate to river environments invaded by buffel grass. These environments have, to our knowledge, never been targeted for burning by Aboriginal peoples. Since the arrival of buffel grass, there is now an extremely high risk that control burns can spread and become out-of-control bushfires.

Even when control burns are successful, the rapid regrowth of buffel grass means firebreaks may only be effective for a short time before risky follow-up burning is required. And there may no longer be a good time of year to burn.




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How invasive weeds can make wildfires hotter and more frequent


Our research suggests that in areas invaded by buffel grass, slow cool winter burns – typical for control burning – can be just as, or more, damaging for trees than fires in hot, windy conditions that often cause fires to spread.

Without more effective management plans and strategies to manage the changing fire threat in central Australia, we face the prospect of a future Tjoritja in which no old-growth trees will remain. This will have a devastating impact on the unique desert mountain ranges.

We need to acknowledge that invasive buffel grass and a changing climate have changed the face of fire risk in central Australia. We need a coordinated response from Australia’s federal and state governments, or it will be too late to stop the ecological catastrophe unfolding before us.


The authors acknowledge the contribution of Shane Muldoon, Sarah White, Erin Westerhuis, CDU Environmental Science and Management students, and NT Parks and Wildlife staff to the research at experimental sites and ongoing tree monitoring in central Australia.The Conversation

Christine Schlesinger, Senior Lecturer in Environmental Science and Ecology, Charles Darwin University and Barry Judd, Professor, Indigenous Social Research, Charles Darwin University

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

How we wiped out the invasive African big-headed ant from Lord Howe Island



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Not welcome: the African big headed ant might be small but it can be a pest if it gets in your home.
CSIRO, Author provided

Ben Hoffman, CSIRO

The invasive African big-headed ant (Pheidole megacephala) was found on Lord Howe Island in 2003 following complaints from residents about large numbers of ants in buildings.

But we’ve managed to eradicate the ant completely from the island using a targeted mapping and baiting technique than can be used against other invasive species.

Up to 15% of Lord Howe Island was thought to be infested with the ant.
CSIRO, Author provided

A major pest

The African big-headed ant is one of the world’s worst invasive species because of its ability to displace some native plants and wildlife, and adversely affect agricultural production.




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In an ant’s world, the smaller you are the harder it is to see obstacles


It’s also a serious domestic nuisance. People can become overwhelmed by the large number of ants living in their buildings – you can’t leave a bit of food lying around, especially pet food, or it will be covered in ants.

It remains unclear how long the ant had been on Lord Howe Island, in the Tasman Sea about 770 km northeast of Sydney, before being found. But it is likely to have been present for at least a decade.

Because of the significant threat this ant posed to the conservation integrity of the island, an eradication program was started. But on-ground work done from 2003 to 2011 had many failings and was not working.

In 2011, I was brought in to oversee the program. The last ant colony was killed in 2016, but it is only now, two years later, that we are declaring Lord Howe Island free from the ants.

No African big-headed ants have been seen on the island for two years.
CSIRO, Author provided

A super colony

The ability to eradicate this ant is largely due to its relatively unique social organisation. The queens don’t fly to new locations to start new nests – instead, they form interconnected colonies that can extend over large areas.

This makes the ant’s distribution easy to map and treat. The ant requires human assistance for long-distance transport, so the ant will only be found in predictable locations where it can be accidentally transported by people.

From 2012 to 2015, all locations on the island where the ant was likely to be present were formally inspected. Priority was given to places where an infestation was previously recorded or considered likely. The populations were mapped, and then treated using a granular bait available at shops.

In the latter years we found 16 populations covering 30 hectares. Limited by poor mapping in the early years, we estimate that the ant originally covered up to 55 hectares, roughly 15% of the island.

Stopping the spread

The widespread distribution of the ant through the populated area of the island is thought to have been aided by the movement of infested mulch and other materials from the island’s Waste Management Facility.

To prevent any more spread of the ant, movement restrictions were imposed in 2003 on the collection of green waste, building materials and other high risk items from the facility.

The baiting program used a product that contains a very low dose of insecticide that has an extremely low toxicity to terrestrial vertebrates such as pet cats and dogs, birds, lizard etc. The toxicant rapidly breaks down into harmless chemicals after exposure to light.

No negative impacts were recorded on any of the native wildlife on the island.

Importantly, the African ant usually kills most other ants and other invertebrates where it is present, so there are few invertebrates present to be affected by the bait.

Ecological recovery of the infested areas was rapid following baiting and the eradication of the African ant.

Another ant invader

One of the main challenges was getting the ground crew to correctly identify the ant.

It turns out there was a second (un-named) big-headed ant species present, also not native to the island, that created a lot of unnecessary work being conducted where the African ant wasn’t present.

CSIRO and Lord Howe Island Board team tackling the African big headed ant problem.
CSIRO, Author provided

Like numerous other exotic ant species present, this second species was of no environmental or social concern, so there are no plans to manage or eradicate it.

The protocols used in this program are essentially the same that are being used in other eradication programs against Electric ant in Cairns and Browsing ant in Darwin and Perth, because those two species also create supercolonies.




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It is highly likely that those programs will also achieve eradication of their respective species, the first instance where an ant species has been eradicated entirely from Australia.

The fire ant program in Brisbane has many similarities, but there are distinct differences in that the ants there don’t form supercolonies that are so easy to map, and the area involved is far greater.The Conversation

Ben Hoffman, Principal research scientist, CSIRO

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

We’ve cracked the cane toad genome, and that could help put the brakes on its invasion



File 20180919 143281 y2z5wl.jpg?ixlib=rb 1.1
Cane toads are on the march, but new genetic research could slow them down.
Michael Linnenbach

Peter White, UNSW; Alice Russo, UNSW, and Rick Shine, University of Sydney

We and our international colleagues have deciphered the genetic code of the cane toad. The complete sequence, published today in the journal GigaScience, will help us understand how the toad can quickly evolve to adapt to new environments, how its infamous toxin works, and hopefully give us new options for halting this invader’s march across Australia.

Since its introduction into Queensland in 1935, the cane toad has spread widely and now occupies more than 1.2 million square kilometres of Australia. It is fatally poisonous to predators such as the northern quoll, freshwater crocodiles, and several species of native lizards and snakes.

Previous attempts to sequence the cane toad, by WA researchers more than 10 years ago, were not successful, largely because the existing technology could not assemble the genetic pieces to create a genome. But thanks to new methods, we have succeeded in piecing together the entire genetic sequence.




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Our team, which also featured researchers from Portugal and Brazil, worked at the Ramaciotti Centre for Genomics at UNSW. This centre played a key role in decoding the genomes of other iconic Australian species, including the koala.

Sequencing, assembling and annotating a genome (working out which genes go where) is a complicated process. The cane toad genome is similar in size to that of humans, at roughly 3 billion DNA “letters”. By using cutting-edge technology, our team sequenced more than 360 billion letters of cane toad DNA code, and then assembled these overlapping pieces to produce one of the best-quality amphibian genomes to date.

We deduced more than 90% of the cane toad’s genes using technology that can sequence very long pieces of DNA. This made the task of putting together the genome jigsaw much easier.

Toxic toads

The cane toad has iconic status in Australia, with many Aussies loving to hate the poisonous invasive amphibian. This is a little unfair. It’s not the cane toad’s fault – it was humans who chose to bring it to Australia.

Our obsession with sugar in the 1800s led to the toad’s introduction to many countries around the world. Wherever sugar cane was planted, the cane toad followed, taken from plantation to plantation by landowners as the warty interlopers travelled from South America to the Caribbean and then on to Hawaii and Australia.

But unlike most other places to which the cane toad was introduced, Australia lacks any native toads of its own. The cane toad’s powerful poisons are deadly to native species that have never before encountered this amphibian’s arsenal.

The cane toad has therefore been subject to detailed evolutionary and ecological research in Australia, revealing not only its impact but also its amazing capacity for rapid evolution. Within 83 years of its introduction, cane toads in Australia have evolved a wide range of modifications that affect their body shape, physiology and behaviour.

For example, cane toads at the invasion front are longer-legged and bolder than those in long-colonised areas and invest less into their immune defences (for a summary, see Cane Toad Wars by Rick Shine).

The new genome will give us insights into how evolution transformed a sedentary amphibian into a formidable invasion machine. And it could give us new weapons to help stop, or at least slow, this invasion.

Cracking the cane toad genome.

Viral control

Current measures such as physical removal have not been successful in preventing cane toads from spreading, so fresh approaches are needed. One option may be to use a virus to help control the toad population.

Viruses such as myxomatosis have been successfully used to control rabbits. But the cane toad viruses studied so far are also infectious to native frogs. The new genome could potentially help scientists hunt for viruses that attack only toads.

In a study published this month, we and other colleagues describe how we sampled genetic sequences from cane toads from different Australian locations, and found three viruses that are genetically similar to viruses that infect frogs, reptiles and fish. These viruses could potentially be used as biocontrol agents, although only after comprehensive testing to check that they pose no danger to any other native species.




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The full cane toad genome will help to accelerate this kind of research, as well as research on the toads’ evolution and its interactions with the wider ecosystem. The published sequence is freely available for anyone to use in their studies. It is one of very few amphibian genomes sequenced so far, so this is also great news for amphibian biologists in general.

As the cane toads continue their march across the Australian landscape, this milestone piece of research should help us put a few more roadblocks in their path.The Conversation

Peter White, Professor in Microbiology and Molecular Biology, UNSW; Alice Russo, PhD candidate, UNSW, and Rick Shine, Professor in Evolutionary Biology, University of Sydney

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