This week the world stopped and stared as the UN announced over a million species are threatened with extinction. In Australia, one threat eclipses all others.
eastern pygmy possum

Feral foxes and cats are known predators of the eastern pygmy possum, which is threatened with extinction. Photo by Phil Spark.

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 introduction of the European red fox (Vulpes vulpes) has been disastrous for our wildlife. Image: Harlz_

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.

A cat kills a galah.

Feral cats are a major driver of biodiversity loss, contributing to 26% of bird, mammal and reptile extinctions. Image credit: Mark Marathon via Wikimedia Commons

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.

The yellow crazy ant is one of the world’s top 100 most invasive pests. They can form huge colonies, totally displacing native animals and seriously disrupting ecological processes.

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 angustifoliaand 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.

A picture of Carp fish
CSIRO has been testing in quarantine a new virus to control invasive carp. CSIRO

We have been testing in quarantine a new virus to control invasive carp. CSIRO

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.

This article was originally published in The Conversation. View the original here.


  1. Well yes, this is true to a point. Although I would have said that we, humanity, are the biggest threat. It is humanity who has introduced, deliberately or not, all of the invasive pests, whether they be plant or animal. Even the problem over abundant species (as mentioned by the previous post) is because humanity has created this by over clearing native vegetation. And we continue to do so at an alarming rate. Continue to remove those areas which gives some protection to our native species, flora and fauna.

  2. Australia should become a cat fee zone with all domestics being neutared.

    1. Or cat owners could be required to keep their cats in enclosures. Dogs aren’t technically allowed to roam and there’s lots of options for enclosing parts of yards that keep cats from roaming but still give them comfortable accommodation.

  3. Foxes, cats, pigs, camels, goats, horses, buffalo, rabbits, mice, cane toads, bees?, humans?
    Love grass, veldt grass, buffel grass, bridal creeper, tagasaste, sharp/spiny rush, interstate wattles and tea tree and eucalypts
    Sparrows, starlings, interstate lorikeets and kookaburras…………….and so many more could be added to the list.
    Probably the potential for disaster of all of them was recognised by many, long before they became so costly to us and our environment! Why wasn’t action taken then, in the beginning?
    Let that be a lesson learnt, NO MORE DELAYS!
    Our government spends about 3 billion dollars a month on defense, keeping us safe from invading foreigners.
    One third of this could probably see all the problems listed above eradicated (over a few years), or well controlled, (how many jobs would be generated in the regional countryside!), keeping our native flora and fauna safe from invading foreigners too? And so much would be learnt about what we were defending, so many would actually come to understand and appreciate, and care about the ‘real Australia’ instead of the overwhelming general ignorance!
    Wouldn’t it be wonderful!
    We have always had so much faith in the CSIRO and looked to their scientists and inventors to solve our country’s problems, is it possible they could be the ones to work out how to undertake and oversee the defense of our heritage?

  4. I visited my sister in Brackenridge, a Brisbane suburb about twenty years ago and noticed cane toads everywhere.
    I visited her again ten years later and there were no cane toads.
    My brother in law explained, the crows had taught themselves a neat trick which kills the toads.
    They hop up to the toad and peck its eye then jump back out of the way so they don’t get poisoned.
    Bush flies are attracted to the wound and lay their eggs in it.
    Soon maggots hatch and they kill the toad by eating it from the inside out.
    A couple of weeks later the crows return and feast on the fat juicy maggots which is their reward.

    I have mentioned this to several groups who are attempting to manage toad number and suggested these crows should be captured and released into other parts of Australia to teach local crows their neat trick, but the scientists don’t seem inclined to even try it which beggars belief.

  5. I would agree with your thinking, around my area stinkwort is rampant along with cactus.But be careful in the thinking its only introduced species causing problems.Here the grey kangaroo are in plaque proportions and coupled with the big dry they have decimated the plants and grasses.People may love the roost but when the quantity of them tips over the scales it puts other plants and animals at risk

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