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

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.

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.

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.

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

‘One of the most damaging invasive species on Earth’: wild pigs release the same emissions as 1 million cars each year

Christopher J. O’Bryan, The University of Queensland; Eve McDonald-Madden, The University of Queensland; Jim Hone, University of Canberra; Matthew H. Holden, The University of Queensland, and Nicholas R Patton, University of CanterburyWhether you call them feral pigs, boar, swine, hogs, or even razorbacks, wild pigs are one of the most damaging invasive species on Earth, and they’re notorious for damaging agriculture and native wildlife.

A big reason they’re so harmful is because they uproot soil at vast scales, like tractors ploughing a field. Our new research, published today, is the first to calculate the global extent of this and its implications for carbon emissions.

Our findings were staggering. We discovered the cumulative area of soil uprooted by wild pigs is likely the same area as Taiwan. This releases 4.9 million tonnes of carbon dioxide each year — the same as one million cars. The majority of these emissions occur in Oceania.

A huge portion of Earth’s carbon is stored in soil, so releasing even a small fraction of this into the atmosphere can have a huge impact on climate change.

The problem with pigs

Wild pigs (Sus scrofa) are native throughout much of Europe and Asia, but today they live on every continent except Antarctica, making them one of the most widespread invasive mammals on the planet. An estimated three million wild pigs live in Australia alone.

A herd of wild pigs — Wild pigs are one of the most widespread invasive animals on Earth.
Shutterstock

It’s estimated that wild pigs destroy more than A$100 million (US$74 million) worth of crops and pasture each year in Australia, and more than US$270 million (A$366 million) in just 12 states in the USA.

Wild pigs have also been found to directly threaten 672 vertebrate and plant species across 54 different countries. This includes imperilled Australian ground frogs, tree frogs and multiple orchid species, as pigs destroy their habitats and prey on them.

Their geographic range is expected to expand in the coming decades, suggesting their threats to food security and biodiversity will likely worsen. But here, let’s focus on their contribution to global emissions.

Their carbon hoofprint

Previous research has highlighted the potential contribution of wild pigs to greenhouse gas emissions, but only at local scales.

One such study was conducted for three years in hardwood forests of Switzerland. The researchers found wild pigs caused soil carbon emissions to increase by around 23% per year.

Similarly, a study in the Jigong Mountains National Nature Reserve in China found soil emissions increased by more than 70% per year in places disturbed by wild pigs.

Wild pigs turn over 36,214 to 123,517 square kilometres of soil each year.
Shutterstock

To find out what the impact was on a global scale, we ran 10,000 simulations of wild pig population sizes in their non-native distribution, including in the Americas, Oceania, Africa and parts of Southeast Asia.

For each simulation, we determined the amount of soil they would disturb using another model from a different study. Lastly, we used local case studies to calculate the minimum and maximum amount of wild pig-driven carbon emissions.

And we estimate the soil wild pigs uproot worldwide each year is likely between 36,214 and 123,517 square kilometres — or between the sizes of Taiwan and England.

Most of this soil damage and associated emissions occur in Oceania due to the large distribution of wild pigs there, and the amount of carbon stored in the soil in this region.

So how exactly does disturbing soil release emissions?

Wild pigs use their tough snouts to excavate soil in search of plant parts such as roots, fungi and invertebrates. This “ploughing” behaviour commonly disturbs soil at a depth of about five to 15 centimetres, which is roughly the same depth as crop tilling by farmers.

Wild pigs uproot soil in search of food, such as invertebrates and plant roots.
University of Kentucky, Department of Forestry and Natural Resources, Forestry Extension.

Because wild pigs are highly social and often feed in large groups, they can completely destroy a small paddock in a short period. This makes them a formidable foe to the organic carbon stored in soil.

In general, soil organic carbon is the balance between organic matter input into the soil (such as fungi, animal waste, root growth and leaf litter) versus outputs (such as decomposition, respiration and erosion). This balance is an indicator of soil health.

When soils are disturbed, whether from ploughing a field or from an animal burrowing or uprooting, carbon is released into the atmosphere as a greenhouse gas.

This is because digging up soil exposes it to oxygen, and oxygen promotes the rapid growth of microbes. These newly invigorated microbes, in turn, break down the organic matter containing carbon.

Wild pigs have a rapid breeding rate, which makes controlling populations difficult.
Shutterstock

Tough and cunning

Wild pig control is incredibly difficult and costly due to their cunning behaviour, rapid breeding rate, and overall tough nature.

For example, wild pigs have been known to avoid traps if they had been previously caught, and they are skilled at changing their behaviour to avoid hunters.

In Australia, management efforts include coordinated hunting events to slow the spread of wild pig populations. Other techniques include setting traps and installing fences to prevent wild pig expansion, or aerial control programs.

Some of these control methods can also cause substantial carbon emissions, such as using helicopters for aerial control and other vehicles for hunting. Still, the long-term benefits of wild pig reduction may far outweigh these costs.

Working towards reduced global emissions is no simple feat, and our study is another tool in the toolbox for assessing the threats of this widespread invasive species.

Christopher J. O’Bryan, Postdoctoral Research Fellow, School of Earth and Environmental Sciences, The University of Queensland; Eve McDonald-Madden, Associate professor, The University of Queensland; Jim Hone, Emeritus professor, University of Canberra; Matthew H. Holden, Lecturer, School of Mathematics and Physics, The University of Queensland, and Nicholas R Patton, Ph.D. Candidate, University of Canterbury

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

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

Corey J. A. Bradshaw, Flinders University; Boris Leroy, Muséum national d’histoire naturelle (MNHN); Camille Bernery, Université Paris-Saclay; Christophe Diagne, Université Paris-Saclay, and Franck Courchamp, Université Paris-SaclayThey’re one of the most damaging environmental forces on Earth. They’ve colonised pretty much every place humans have set foot on the planet. Yet you might not even know they exist.

We’re talking about alien species. Not little green extraterrestrials, but invasive plants and animals not native to an ecosystem and which become pests. They might be plants from South America, starfish from Africa, insects from Europe or birds from Asia.

These species can threaten the health of plants and animals, including humans. And they cause huge economic harm. Our research, recently published in the journal Nature, puts a figure on that damage. We found that globally, invasive species cost US$1.3 trillion (A$1.7 trillion) in money lost or spent between 1970 and 2017.

The cost is increasing exponentially over time. And troublingly, most of the cost relates to the damage and losses invasive species cause. Meanwhile, far cheaper control and prevention measures are often ignored.

Yellow crazy ants attacking a gecko — Yellow crazy ants, such as these attacking a gecko, are among thousands of invasive species causing ecological and economic havoc.
Dinakarr, CC0, Wikimedia Commons

An expansive toll

Invasive species have been invading foreign territories for centuries. They hail from habitats as diverse as tropical forests, dry savannas, temperate lakes and cold oceans.

They arrived because we brought them — as pets, ornamental plants or as stowaways on our holidays or via commercial trade.

The problems they cause can be:

ecological, such as causing the extinction of native species
human health-related, such as causing allergies and spreading disease
economic, such as reducing crop yields or destroying human-built infrastructure.

In Australia, invasive species are one of our most serious environmental problems – and the biggest cause of extinctions.

Feral animals such as rabbits, goats, cattle, pigs and horses can degrade grazing areas and compact soil, damaging farm production. Feral rabbits take over the burrows of native animals, while feral cats and foxes hunt and kill native animals.

Wetlands in the Northern Territory damaged by invasive swamp buffalo (*Bubalus bubalis*)
Warren White

Introduced insects, such as yellow crazy ants on Christmas Island, pose a serious threat to a native species. Across Australia, feral honeybees compete with native animals for nectar, pollen and habitat.

Invasive fish compete with native species, disturb aquatic vegetation and introduce disease. Some, such as plague minnows, prey on the eggs and tadpoles of frogs and attack native fish.

Environmental weeds and invasive fungi and parasites also cause major damage.

Of course, the problem is global – and examples abound. In Africa’s Lake Victoria, the huge, carnivorous Nile perch — introduced to boost fisheries – has wiped out more than 200 of the 300 known species of cichlid fish — prized by aquarium enthusiasts the world over.

And in the Florida Everglades, thousands of five metre-long Burmese pythons have gobbled up small, native mammals at alarming rates.

In Africa, numbers of the beautiful cichlid fish have been decimated by Nile perch.
Shutterstock

Money talks

Despite the serious threat biological invasions pose, the problem receives little political, media or public attention.

Our research sought to reframe the problem of invasive species in terms of economic cost. But this was not an easy task.

The costs are diverse and not easily compared. Our analysis involved thousands of cost estimates, compiled and analysed over several years in our still-growing InvaCost database. Economists and ecologists helped fine-tune the data.

The results were staggering. We discovered invasive species have cost the world US$1.3 trillion (A$1.7 trillion) lost or spent between 1970 and 2017. The cost largely involves damages and losses; the cost of preventing or controlling the invasions were ten to 100 times lower.

Clearly, getting on top of control and prevention would have helped avoid the massive damage bill.

Average costs have been increasing exponentially over time — trebling each decade since 1970. For 2017 alone, the estimated cost of invasive species was more than US$163 billion. That’s more than 20 times higher than the combined budgets of the World Health Organisation and the United Nations in the same year.

Perhaps more alarming, this massive cost is a conservative estimate and likely represents only the tip of the iceberg, for several reasons:

we analysed only the most robust available data; had we included all published data, the cost figure would have been 33 times higher for the estimate in 2017
some damage caused by invasive species cannot be measured in dollars, such as carbon uptake and the loss of ecosystem services such as pollination
most of the impacts have not been properly estimated
most countries have little to no relevant data.

A bucket by a lake with a sign reading 'Biosecurity station. Please dip your feet and nets' — Prevention strategies, such as biosecurity controls, are a relatively cheap way to deal with invasive species.
Shutterstock

Prevention is better than cure

National regulations for dealing with invasive species are patently insufficient. And because alien species do not respect borders, the problem also requires a global approach.

International cooperation must include financial assistance for developing countries where invasions are expected to increase substantially in the coming decades, and where regulations and management are most lacking.

Proactive measures to prevent invasion must become a priority. As the old saying goes, an ounce of prevention is better than a pound of cure. And this must happen early – if we miss the start of an invasion, control in many cases is impossible.

More and better research on the economic costs of biological invasions is essential. Our current knowledge is fragmented, hampering our understanding of patterns and trends, and our capacity to manage the problem efficiently.

We hope quantifying the economic impacts of invasive species will mean political leaders start to take notice. Certainly, confirmation of a A$1.7 trillion bill should be enough to get the ball rolling.

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; Boris Leroy, Maître de conférences en écologie et biogéographie, Muséum national d’histoire naturelle (MNHN); Camille Bernery, Doctorante en écologie des invasions, Université Paris-Saclay; Christophe Diagne, Chercheur post-doctorant en écologie des invasions, Université Paris-Saclay, and Franck Courchamp, Directeur de recherche CNRS, Université Paris-Saclay

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

The diet of invasive toads in Mauritius has some rare species on the menu

The invasive guttural toad.
Author supplied.

James Baxter-Gilbert, Stellenbosch University

The guttural toad (Sclerophrys gutturalis) is a common amphibian found in much of sub-Saharan Africa, from Angola to Kenya and down to eastern South Africa. With such a wide geographic range, and a liking for living in human-disturbed areas, it’s often seen in people’s backyards. Around gardens it can be thought of as a helpful neighbour, as it is a keen predator of insects and other invertebrates that may try to eat plants. Yet it also has the potential to be ecologically hazardous outside its native range – and this toad is an accomplished invader.

In the Mascarene Archipelago in the Indian Ocean, far from mainland Africa, these toads have been an established invasive species for almost 100 years. In 1922, the director of dock management in Port Louis, Mauritius, deliberately released guttural toads in an attempt to control cane beetles – a pest of the country’s major crop, sugar cane. This attempt at biocontrol failed, but the toads appeared to thrive and rapidly spread across the island.

Mauritius had no native amphibian species for it to compete with, and no native predators with a recent evolutionary history with toads. In mainland Africa these toads would have to divide resources, like food, with a host of native amphibians and deal with an array of native birds, mammals and snakes that evolved feeding on them. But without these challenges on Mauritius, the toads colonised the entire island rapidly.

Most toads are generalist predators and hunt a wide variety of prey, more or less eating whatever they can fit in their mouth. So as the guttural toad’s population numbers grew through the decades, so too did the concerns from Mauritian ecologists about the impact on native fauna. Anecdotal accounts as early as the 1930s suggest that the toads were having a negative impact on endemic invertebrate populations. In fact it has been suggested that the toads may have been a driver in the decline, and possible extinction, of endemic carabid beetles and snails.

But it’s only recently that the toad’s diet in Mauritius has been examined closely. In our new study we examined the stomach contents of 361 toads collected in some of the last remaining native forests of Mauritius.

By knowing more about what species the toads are eating, and which groups they favour, our research may help inform toad control actions to protect areas with known sensitive species.

In the belly of the beast

Through our research we were able to identify almost 3,000 individual prey items, encompassing a wide variety of invertebrates like insects, woodlice, snails, spiders, millipedes and earthworms.

This research also went one step further to examine the prey preference of the toads. In general, they seemed to favour, some of the more abundant and common prey species. These included ants and woodlice, which made up about two-thirds of their overall diet.

These findings may suggest that the toads were able to identify a readily available food source, and this may have fuelled their invasive population growth. Yet they are also eating prey that represents a more serious conservation concern.

Inside the toads we found 13 different species of native snail, most of which were island endemics. Four species are listed as being vulnerable to extinction and one, Omphalotropis plicosa, being critically endangered – having been presumed extinct until it was rediscovered in 2002. Understandably, we found it very troubling to find a “Lazarus species” within the stomach of an invasive predator.

Unanswered questions

These early insights into the native species now being hunted by a widespread and voracious predator raise new research questions. To understand the greater impact the toads are having on native species much more work is required to understand their prey’s population dynamics so we can determine if the toad’s invertebrate “harvest” is contributing to declines.

Furthermore, how does the toad’s invasive diet in Mauritius compare with that of other invasive populations, like those in Réunion or Cape Town – is their invasive success linked to a common prey type? And how does it compare with their diet in their own native species range?

Our study could only examine what they are eating currently, but Mauritius has seen numerous species decline over the past 100 years. What role did the toad play in these losses? Perhaps they historically fed more readily on creatures that were more abundant in the past, but had to switch their favour to ants and woodlice when the populations of other species dropped. We may never know.

What is clear is that there is much to learn about the habits of this far-from-home amphibian and its impact on the ecosystems it has invaded.

James Baxter-Gilbert, Postdoctoral Fellow, Centre for Invasion Biology (C·I·B), Department of Botany & Zoology, Stellenbosch University

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

The buffel kerfuffle: how one species quietly destroys native wildlife and cultural sites in arid Australia

Buffel grass surrounding *Hakea divaricata*, a bushfood and medicine tree.
Ellen Ryan-Colton, Author provided

Christine Schlesinger, Charles Darwin University; Ellen Ryan-Colton, Charles Darwin University; Jennifer Firn, Queensland University of Technology, and John Read

Many of us are aware of the enormous destruction feral cats inflict on Australia’s native wildlife, but there’s another introduced species that will cause at least as much harm if left unmanaged — yet it receives far less attention.

We’re referring to buffel grass (Cenchrus ciliaris), a plant native to parts of Africa and Asia that has been widely introduced elsewhere for pasture and to stabilise soils.

Buffel is fast growing, deep rooted and easy to establish, with each plant producing thousands of seeds. But these very characteristics for which it was prized have caused it to spread much further than ever planned.

We recently published two studies on buffel grass. One looked at just how serious the buffel invasion is to humans and wildlife by comparing it to other high-profile threats such as cats and foxes. The other study found that when buffel was removed, native wildlife quickly bounced back.

A catastrophic threat to wildlife

Buffel is now one of the worst invaders of dryland ecosystems worldwide. In Australia, this single species has replaced once diverse communities of native grasses and wildflowers across vast tracks of land. For example, most conservation reserves in the southern part of the NT have been invaded, including parts of Uluru-Kata Tjuta National Park.

Because it grows so thickly, the dense grassy fuel can feed bigger, hotter and sometimes unexpected fires. These new fires are a risk to wildlife, humans and large, old trees.

Buffel and fire affected shrubs starting to burn — Buffel grass promotes new fire risks.
Jennifer Firn, Author provided

Our study compared buffel to threats posed by changed fire regimes, feral predators (cats and foxes) and feral herbivores (rabbits and camels). We found buffel was equal to feral cats and foxes in terms of future risk to biodiversity.

Feral cats are currently listed as threatening some 139 species under national environment legislation, including the night parrot and the central rock rat. Each year across Australia, feral cats kill more than three billion animals.

Buffel is formally listed as threatening 27 species under this legislation, such as the floodplain skink (buffel can choke its burrows). But because there has been much less research on the impacts of buffel, this number is likely a significant underestimate.

Unlike cats, buffel impacts whole plant communities and the animals they support. For example, when large old trees are burnt, birds that rely on tree hollows for nesting can no longer breed successfully.

Buffel grass surrounds bushfood wattleseed. — Buffel grass surrounding wattleseed, a bushfood.
Ellen Ryan-Colton, Author provided

What’s more, buffel has only spread widely in the last 20-30 years, which means its full impact on ecosystems has not yet been realised. In fact, 70% of the Australian continent has suitable conditions for buffel growth and could, in time, become invaded.

In contrast, cats have already roamed Australia for more than 200 years and, tragically, have caused many species, like the lesser stick-nest rat, to become extinct.

A social and cultural threat for Aboriginal people

Our study found buffel ranked higher than any other environmental threat in terms of its social and cultural impacts for Aboriginal people.

Because buffel is valued as a pasture grass in some regions, much debate has focused on its agro‐economic benefits versus environmental costs.

Meanwhile, the views and values of Aboriginal custodians of inland Australia have remained marginalised. It’s time this changes.

Nyanyu Watson showing how it’s harder to see animal tracks in areas occupied by buffel grass.
Ellen Ryan-Colton, Author provided

While feral cats and buffel both threaten culturally important wildlife, buffel is also causing the decline of valued plant foods and medicines.

For example, native desert raisin (Solanum centrale) — “katjirra” to Western Arrernte people and “kampuṟarpa” to Pitjantjatjara people — remains an important staple food across central Australia and is part of Australia’s living cultural heritage.

However, it is becoming harder for women to find and collect as buffel takes over country.

Buffel grass growing right under desert fig, a bushfood that’s sensitive to fire.
Ellen Ryan-Colton, Author provided

Buffel also damages important cultural sites by bringing fire and choking water holes. Thick grass makes it difficult to walk through country and it’s now hard to see tracks or animals.

Together with the loss of species, this inhibits the transfer of cultural knowledge from one generation to another.

The return of native wildlife

Buffel responds well to herbicide in smaller areas, and spread can be slowed or stopped by treating isolated infestations.

For six years, we tracked the response of native plants and animals (particularly lizards) after buffel was treated at six sites in the Tjoritja National Park near Alice Springs. And we found biodiversity soon bounced back.

A buffel grass removal experiment, near Alice Springs.
Christine Schlesinger, Author provided

Following good rains, native plants like billy buttons and golden everlastings that had just been hanging on quickly re-established in areas where buffel was treated. And as native plant communities were restored, a range of lizards and other wildlife returned, too.

Birds such as Australian ring-neck parrots and red-tailed black-cockatoos began to selectively use the treated areas, foraging on seeds on the more open ground.

Ants also became much more abundant and diverse where buffel was removed. Ants play an important role in ecosystems, for example, by dispersing seeds. This has likely been diminished in buffel-occupied areas.

Fire-tailed skink — A fire-tailed skink at one of the the buffel removal sites.
Christine Schlesinger, Author provided

Importantly, while research demonstrates the potential for ecosystem recovery following effective control, the negative effects of buffel on fauna increased in areas where we did nothing.

Where to from here?

The findings from both our studies underline the urgent need for management on a much larger scale than what is currently possible, and prevention of further spread.

It’s clear a nationally coordinated response is required, along with policies that support positive local initiatives.

Creating and maintaining large buffel-free sanctuaries in areas not yet invaded could help to protect biodiversity in the future. But we found the cost of maintaining these could be an estimated 40–50 times more than other pest-free sanctuaries, if restricted to current methods of control.

This is why Australia needs new, cost-effective, culturally appropriate and safe control options, rolled out on a broad scale. We stress the need for Aboriginal people from regions affected by buffel and prone to invasion to be central to discussions and the development of solutions.

It’s also important to note controlling buffel doesn’t require its eradication from pastoral regions where it’s valued. It does, however, require a national commitment and dedicated research, with strategic, coordinated and committed action.

Christine Schlesinger, Senior Lecturer in Environmental Science and Ecology, Charles Darwin University; Ellen Ryan-Colton, PhD candidate, Charles Darwin University; Jennifer Firn, Professor, Queensland University of Technology, and John Read, Associate Lecturer, Ecology and Environmental Sciences

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

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.

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.

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.

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.

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.

The mystery of the Top End’s vanishing wildlife, and the unexpected culprits

A brush-tailed rabbit-rat, one of the small mammals disappearing in northern Australia.
Cara Penton, Author provided

Alyson Stobo-Wilson, Charles Darwin University; Brett Murphy, Charles Darwin University; Graeme Gillespie, University of Melbourne; Jaana Dielenberg, The University of Queensland, and John Woinarski, Charles Darwin University

Only a few decades ago, encountering a bandicoot or quoll around your campsite in the evening was a common and delightful experience across the Top End. Sadly, our campsites are now far less lively.

Northern Australia’s vast uncleared savannas were once considered a crucial safe haven for many species that have suffered severe declines elsewhere. But over the last 30 years, small native mammals (weighing up to five kilograms) have been mysteriously vanishing across the region.

The reason why the Top End’s mammals have declined so severely has long been unknown, leaving scientists and conservation managers at a loss as to how to stop and reverse this tragic trend.

The author smiles at an adorable glider in a little blanket she's holding. — Alyson Stobo-Wilson with a savanna glider. Gliders are among the mammals rapidly declining in northern Australia.
Alyson Stobo-Wilson, Author provided

Our major new study helps unravel this longstanding mystery. We found that the collective influence of feral livestock — such as buffaloes, horses, cattle and donkeys — has been largely underestimated. Even at quite low numbers, feral livestock can have a big impact on our high-value conservation areas and the wildlife they support.

The race for solutions

In 2010, Kakadu National Park conducted a pivotal study on Top End mammals. It found that between 1996 and 2009, the number of native mammal species at survey sites had halved, and the number of individual animals dropped by more than two-thirds. Similar trends have since been observed elsewhere across the Top End.

Given the scale and speed of the mammal declines, the need to find effective solutions is increasingly urgent. It has become a key focus of conservation managers and scientists alike.

The list of potential causes includes inappropriate fire regimes, feral cats, cane toads, feral livestock, and invasive weeds.

Many small and medium-sized mammals are in rapid decline in northern Australia.

With limited resources, it’s essential to know which threats to focus on. This is where our study has delivered a major breakthrough.

We looked for patterns of where species have been lost and where they are hanging on. With the help of helicopters to reach many remote areas, we used more than 1,500 “camera traps” (motion-sensor cameras to record mammals) and almost 7,500 animal traps (such as caged traps) to survey 300 sites across the national parks, private conservation reserves and Indigenous lands of the Top End.

A new spotlight on feral livestock

We found most parts of the Top End have very few native mammals left. The isolated areas where mammals are persisting have retained good-quality habitat, with a greater variety of plant species and dense shrubs and grasses.

This habitat provides more shelter and food for native mammals, and has fewer cats and dingoes, which hunt more efficiently in open areas. In contrast, sites with degraded habitat have much less food and shelter available, and native mammals are more exposed to predators.

Six dark coloured horses roam among sparse trees in the Top End. — Feral horses can overgraze and trample over habitat, making it far less suitable for small native mammals.
Jaana Dielenberg, Author provided

Across northern Australia, habitat quality is primarily driven by two factors: bushfires and introduced livestock, either farmed or feral.

Our surveys revealed that areas with more feral livestock have fewer native mammals. This highlights that the role of feral livestock in the Top End’s mammal declines has previously been underestimated.

Even at relatively low densities, feral livestock are detrimental to small mammals. Through overgrazing and trampling, they degrade habitat and reduce the availability of food and shelter for native mammals.

Frequent, intense fires also play a big role. Australia’s tropical savannas are among the most fire-prone on Earth, but fires that are too frequent, too hot and too extensive remove critical food and shelter.

Yet, even if land managers can manage fires to protect biodiversity, for example by reducing the occurrence of large, intense fires, the presence of feral livestock will continue to impede native mammal recovery.

A wild buffalo walks over grass, in front of trees. — Even small numbers of feral livestock can play a big role in native mammal declines.
Northern Territory Government, Author provided

A new way to manage cats

Cats have helped drive more than 20 Australian mammals to extinction. So it’s not surprising we found fewer native mammals at our sample sites where there were more cats.

However, our results suggest the best way to manage the impact of cats in this region may not be to simply kill cats, which is notoriously difficult across vast, remote landscapes. Instead, it may be more effective to manage habitat better, tipping the balance in favour of native mammals and away from their predators.

A striped, ginger cat with shining eyes looks at the camera at night. — A feral cat at one of the study sites. Cats have helped cause more than 20 native mammal extinctions.
Northern Territory Government, Author provided

The combination of prescribed burning to protect food and shelter resources, and culling feral livestock, might be all that’s needed to support native mammals and reduce the impact of feral cats.

What about dingoes?

Many scientists have suggested dingoes could also be part of the solution to reducing cat impacts — as cats are believed to avoid dingoes. With this in mind, we explored the relationship between the two predators in this study.

A brownish motion detection camera trap strapped to a tree. — One of more than 1,000 motion detection cameras used in this study.
Jaana Dielenberg, Author provided

We found no evidence dingoes influenced the distribution of feral cats. In fact, survey sites with more dingoes had fewer native small mammals, suggesting a negative impact by dingoes.

But, unlike cats, culling dingoes is not an option because they provide other important ecological roles, and are culturally significant for Indigenous (and non-Indigenous) Australians.

Controlling herbivores, not predators

Our study suggests an effective way to halt and reverse Top End mammal losses is to protect and restore habitat. For example, by improving fire management and controlling feral livestock through culling.

It is also very important to conserve the environments that still have high-quality habitat and healthy mammal communities, such as the high-rainfall areas along the northern Australian coast. These areas provide refuge for many of our most vulnerable mammal species.

A photo from a camera trap showing a black-footed tree-rat on its hind legs. — The native black-footed tree-rat has had major declines across northern Australia. It’s vulnerable to cats and is now restricted to areas that still have good quality habitat, fewer herbivores and less frequent fire.
Hugh Davies, Author provided

The tropical savannas of northern Australia are the largest remaining tract of tropical savanna on Earth and new species are still being discovered.

While there’s more research to be done, it’s crucial we start managing habitat better, before we lose more of our precious mammal species.

The authors would like to gratefully acknowledge the support from many Indigenous ranger groups, land managers and Traditional Owners. This includes the Warddeken, Bawinanga, Wardaman and Tiwi rangers, the Traditional Owners and land managers of Kakadu, Garig Gunak Barlu, Judbarra/Gregory, Litchfield and Nitmiluk National Parks, Djelk, Warddeken and Wardaman Indigenous Protected Areas, and Fish River Station and was facilitated by the Northern, Tiwi and Anindilyakwa Land Councils.

Alyson Stobo-Wilson, Postdoctoral Research Associate, Charles Darwin University; Brett Murphy, Associate Professor / ARC Future Fellow, Charles Darwin University; Graeme Gillespie, Honorary Research Fellow, University of Melbourne; Jaana Dielenberg, Science Communication Manager, The University of Queensland, and John Woinarski, Professor (conservation biology), Charles Darwin University

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

When introduced species are cute and loveable, culling them is a tricky proposition

Lily van Eeden, University of Sydney; Chris Dickman, University of Sydney; Jeremy T. Bruskotter, The Ohio State University; Mathew Crowther, University of Sydney, and Thomas Newsome, University of Sydney

Almost one in five Australians think introduced horses and foxes are native to Australia, and others don’t want “cute” or “charismatic” animals culled, even when they damage the environment. So what are the implications of these attitudes as we help nature recover from bushfires?

Public opposition to culling programs is often at odds with scientists and conservationists.

These tensions came to the fore last month when scientists renewed calls for a horse-culling program to protect native species in Kosciusko National Park – a move strongly opposed by some members of the public.

To manage the environment effectively, including after bushfires, we need to understand the diversity of opinion on what constitutes a native animal, and recognise how these attitudes can change.

Governments are responding

In Australia, native species are usually defined as those present before European settlement in 1788. Lethal pest control usually targets species introduced after this time, such as horses, foxes, deer, rabbits, pigs, and cats.

But fire makes native fauna more vulnerable to introduced predators. Fire removes ground layer vegetation that small wildlife would use as protective cover. When this cover is gone, these animals are easier targets for predators like cats and foxes.

State governments have started to respond to this impending crisis. In January, the New South Wales government announced its largest ever program to control feral predators, in an effort to protect native fauna after the fires.

The plan includes 1500-2000 hours of aerial and ground shooting of deer, pigs, and goats and distributing up to a million poison baits targeting foxes, cats, and dingoes over 12 months.

Similarly, the Victorian government announced a A$17.5 million program to protect biodiversity the fires affected, including A$7 million for intensified management of threats like introduced animals.

But will the public be on board? Widespread media coverage of the recent fires and their impacts on wildlife, including the loss of more than a billion animals, might garner support for protecting native wildlife from pests.

On the other hand, efforts to manage animals such as cats and horses might be hampered by a lack of public support for culling charismatic animals that many people value or view as belonging in Australia now.

Different folks, different strokes

The distinctions many Australians draw – native animals are “good” and introduced species are “bad” – shape how people view conservation efforts. A survey we conducted in 2017 found people more likely to disapprove of lethal methods for managing species they perceived to be native.

In the same survey, we found nearly one in five Australians considered horses and foxes to be native to Australia.

This suggests either that a) people lack knowledge of Australia’s natural history or b) people disagree with conservationists’ definition of animal “nativeness”.

Calls to manage horses to prevent environmental degradation in Australian national parks are hugely controversial, with many people arguing the horses belong now.
Shutterstock

Many introduced species, such as horses and foxes, have existed in Australia for more than a century and have established populations across much of the country. It’s unlikely they’ll ever be eradicated.

Some people, including scientists, say we should just accept introduced species as part of Australia’s fauna. They argue current management justifies killing based on moral, not scientific judgements and introduced animals may increase biodiversity.

But the issue remains extremely divisive. A central tenet of traditional conservation is that humans have a duty to protect native species and ecosystems from the threat introduced species pose. It’s difficult to do this without culling introduced animals.

Animal welfare concerns may also drive opposition to culling, taking the view that all animals, even non-natives, have intrinsic value and the right to live.

What’s more, non-native culling programs can be controversial when the animal is considered “cute” or “charismatic”, or of cultural value. For example, a plan to cull feral horses in the Kosciusko National Park in 2018 was met with public outrage, prompting the NSW government to overturn the decision.

Yet protecting introduced species in national parks goes against the very reason they were created – to conserve native ecosystems and species.

Some animals are more equal than others

When analysing public attitudes towards various species, we must also consider how attitudes shift over time.

In Australia, non-native animals such as domestic camels and donkeys were considered useful for transport and highly valued. But we ultimately turned them loose and relabelled them as pests when we started using cars.

We asked the Australian public whether they viewed dingoes, horses, and foxes as native or non-native in Australia.
van Eeden et al. (2020)

Interestingly, we’ve already accepted some introduced species as native. Humans brought dingoes to Australia at least 3,500 years ago. They’re described as native under Australian biodiversity legislation, and 85% of our 2017 survey participants considered dingoes to be native.

Perhaps its only a matter of time until more recently arrived species like horses and foxes are counted as native. Some scientists argue this shift should be based on how ecosystems and species adapt to these new arrivals. For example, some small Australian mammals show fear of dingoes or dogs, but they haven’t yet learnt to fear cats.

Native species can be pests too

Native species, such as kangaroos and possums, may also be culled if they’re perceived to be overabundant or damaging economic interests like agriculture.

While the plight of bushfire-affected koalas on Kangaroo Island attracted considerable media interest, and the immediate welfare of any animal affected by fires is always a concern, koalas were actually introduced there.

They’ve been managed as a pest on Kangaroo Island for more than 20 years, and it’s unlikely the rescued koalas will be returned to the island. In this case, public concern transcends the distinction between native and introduced.

Public perception is important

We might never all agree on how best to manage native and non-native species. But effective environmental management, including after bushfires, requires understanding the diversity of opinion.

Doing so can help to develop management plans the public supports and allow effective communication about management that is controversial.

In fact, the NSW Office of Environment and Heritage did undertake an extensive public consultation process in developing their horse management plan for Kosciuszko National Park, but it wasn’t used after the “brumby bill” gave horses protection in 2018.

With human lives and many animal lives lost, response to the bushfires is already highly emotive. Failure to consider public attitudes towards managing animals will lead to backlash, wasted money and time, and continuing decline of the native species whose conservation is the goal of these actions.

Lily van Eeden, PhD Candidate in Human-Wildlife Conflict, University of Sydney; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; Jeremy T. Bruskotter, Professor, School of Environment and Natural Resources, The Ohio State University; Mathew Crowther, Associate professor, University of Sydney, and Thomas Newsome, Lecturer, University of Sydney

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

Non-native species should count in conservation – even in Australia

Australia is home to many new species, including wild camels found nowhere else on Earth.
Author provided

Arian Wallach, University of Technology Sydney; Chelsea Batavia, Oregon State University; Danielle Celermajer, University of Sydney; Daniel Ramp, University of Technology Sydney; Erick Lundgren, University of Technology Sydney, and Esty Yanco, University of Technology Sydney

As the world struggles to keep tabs on biodiversity decline, conservation largely relies on a single international database to track life on Earth. It is a mammoth and impressive undertaking – but a glaring omission from the list may be frustrating conservation efforts.

The International Union for the Conservation of Nature’s Red List aims to be a “complete barometer of life”. But non-native wildlife is excluded from the list.

Our study, published today in the journal Conservation Biology, questions the wisdom of this omission. It means, for example, vulnerable species facing existential threats in their “home country” may be exterminated freely in another. Excluding these animals, such as wild camels in Australia, and rare Australian frogs living overseas, distorts conservation science.

What counts as ‘native’?

The concept of “native” draws a sharp line between species that count and those that don’t. It is essentially an ethical choice, and a disputed one at that. Regardless of whether one defends or disputes the concept, it is problematic to use a moral term to filter a critical source of scientific data.

Trash Animals: How We Live with Nature’s Filthy, Feral, Invasive, and Unwanted Species.

The invisible components of biodiversity – those populations excluded from conservation’s definition of life – can be found in trash lists, where they are described as invasive, aliens, pests, and feral.

So what does the world look like if we include all wildlife in biodiversity assessments? We rummaged around in the “trash piles” to find out.

When all life counts

By focusing on Australian non-native vertebrate species – amphibians, birds, fishes, mammals, and reptiles – we did something many conservationists would find unthinkable. We added unloved species such as feral cats, cane toads, the Indian myna, and carp to Australia’s biodiversity counts.

We created maps showing the range of 87 species whose ancestors were introduced into Australia, and 47 species native to Australia that were introduced elsewhere, since European colonisation.

Many of these so-called invasive species are at risk of extinction in their native ranges; 32% are assessed as threatened or decreasing in the Red List. For 15 of them, non-native ranges provide a lifeline.

Australia’s vertebrate species that are threatened or near threatened in their native ranges with significant populations overseas. From left-to-right: Indian hog deer, banteng, wild cattle, wild water buffalo, wild camel; wild goat, carp, wild donkey, brumby, Mozambique tilapia; European rabbit, Javan rusa, sambar deer, and (emigrants) green and golden bell frog, growling grass frog.
Arian Wallach et al

Not only does Australia contribute to the survival and flourishing of these species, but immigrant vertebrates have also added 52 species to the number of vertebrate species in Australia (after accounting for extinctions).

This number in no way indicates that non-native species replace or make up for those that have been lost. And it does not exonerate humans of their role in causing extinctions. But the current data do not even allow us to acknowledge that these species exist.

Because they are not counted in conservation, these non-native populations are subjected to mass eradication programs. Paradoxically, in assessing how such programs are justified, we found conservation is the most frequently cited reason for killing these wild animals.

Dromedary camels were extinct in the wild for some 5,000 years until they “went feral” in Australia, where they are now endemic. Rather than celebrating what is arguably the most extraordinary rewilding event in the world, wild camels were declared a pest. Between 2009 and 2013, Australia spent A$19 million to gun down 160,000 individuals of a species found nowhere else on Earth in the wild.

Likewise, 89% of the global distribution of Javan rusa, a deer species vulnerable to extinction, is in Australia. As pest, they are culled and hunted for sport.

Stated motivations for killing Australia’s immigrant vertebrate wildlife, shown as percentages of species targeted per taxonomic group. Numbers above bars indicate absolute number of species targeted.

Nativism not only renders countless species invisible, along with their unique and fascinating ecologies; it also exposes them to unfettered, unscientific, unmonitored, and unlamented mass killing programs.

Mass killing of non-native species, if questioned at all, is generally explained as protecting native species. But ecology is complex. One cannot simply assume that all non-native populations, in all contexts, do nothing but harm.

Where non-native species do contribute to the loss of native species, humans need to confront the ethical complexities and shoulder real responsibility, rather than simply reach for a gun as a first solution.

In many situations changing harmful human behaviours, like persecuting apex predators such as dingoes, can solve problems that appear to be caused solely by non-native species.

Irrespective of whether we value non-native species or not, there is no scientific justification for expunging large swaths of the living world from conservation data. Smuggling ethically dubious distinctions into data harms conservation science, and has grave repercussions.

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.

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.

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.

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.

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.

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.

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.

Huge economic burden

Worst of the worst

Variation across regions

Better assessments needed

A constant threat

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The problem with pigs

Their carbon hoofprint

So how exactly does disturbing soil release emissions?

Tough and cunning

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An expansive toll

Money talks

Prevention is better than cure

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In the belly of the beast

Unanswered questions

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A catastrophic threat to wildlife

A social and cultural threat for Aboriginal people

The return of native wildlife

Where to from here?

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It sounds good on paper

Conflicting moral standpoints

Evolutionary biases

More harm than good

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The race for solutions

A new spotlight on feral livestock

A new way to manage cats

What about dingoes?

Controlling herbivores, not predators

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Governments are responding

Different folks, different strokes

Some animals are more equal than others

Native species can be pests too

Public perception is important

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What counts as ‘native’?

When all life counts

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Australia’s number one threat

The effects of invasive species are getting worse

The cost to Australia

From island to savannah

What solutions do we have?

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