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. ‘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.’ It is widely accepted that foxes and cats have major impacts on medium weight range mammals in central and northern Australia as well as south-west Australia.

    However, mainland south-east Australia is a different story, possibly because of higher vegetation cover affording protection to prey species. The extinction debt from the fox was relatively small and has been paid: pademelon, bettong and eastern barred bandicoot. Now we have a situation in which mammalian predators are required to control mammalian herbivores to protect ecosystem stability and diversity. Only the red fox can now do this over large areas, otherwise forget about having river red gums etc. Ecosystems with no mammalian predators go into ecological meltdown affecting far more species as evidenced by predator exclosures in the region. The cat is not known to have caused the extinction of any species in south-east Australia, so appears to have no extinction debt.


  2. @Max Bancroft
    What a fascinating story. Would be cool if your BIL could capture some footage of this, sounds like something out of an Attenborough documentary

  3. Why not positive action on all feral animals .. The rabbit is out of control on our farm, Fox controllable . Deer pigs not to us yet. Why we cannot use any method to get rid of them is beyond me. DEAD is the only solution BUt we all do our bit at different times.
    Why don’t we have 2 weeks a year 6 months apart when every body is out to exterminate as many ferals as possible from Urban areas to parks as well as our Farms

  4. Why can’t we put a price on foxes, make cats have to be enclosed ie aviaries in backyards by law. Rabbits should be harvested for food instead of poisoning RM Williams now sources their rabbit fur for hats overseas as they say there are not enough here How Ridiculous, we need to use good ol common sense and go back to the old ways employ people to do these things.

  5. Its not those animals but these animals. These animals called homo sapiens. Too many, too many on the planet. No one’s saying it but it seems to be the root cause of our problems….global warming, loss of habitat to population centres or food crops. Loss of species could be managed with effort but too much focus on getting elected not fixing the problem. And who would dare put a virus into the carp when they are the most widely eaten fish in the world. Put a $1.00 dollar per fish bounty and facilitate the export of the fish to our near neighbours and it will be similar to the goats. There are a lot less feral goats now that goat meat has reached $9.20/kg.

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