Pest plants and animals cost Australia around $25bn a year – and it’s going to get worse

Unfortunately, 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 not only cause extinctions and loss of biodiversity, they also create a heavy economic burden. Our to research, published today, reveals that 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 kind ever published in this country – also reveals that 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 each year on invasive species.

Feral cats are Australia’s costliest invasive species.
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Huge economic burden

Invasive species are those that are not native to a particular ecosystem. They are introduced accidentally or on purpose and become parasites.

Some costs involve direct damage to agriculture, such as fruit-destroying insects or fungi. 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 estimated the global cost of invasive species at A$1.7 trillion. But this is most certainly a gross underestimate because many data are missing.



Read more: Attack of alien invaders: Pest plants and animals leave a chilling $1.7 trillion bill


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

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

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

The worst of the worst

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

Feral cats are a major driver of extinctions in Australia, so perhaps the investment to limit their damage is worth it.

The plague of Tasmania – groundsel (Senecio jacobaea)
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As a group, the management and control of invasive plants has proven to be the worst of all, collectively costing around A$200 billion. Among these, annual ryegrass, parthenium and ragwort were the costliest culprits due to the great effort required to eradicate them from croplands.

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

Australia’s 10 costliest invasive species.
CJA Bradshaw

Variation by region

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

Imported fire ants are Queensland’s costliest species and ragwort is Tasmania’s economic blight.

the common heliotrope is the most expensive species in South Australia and Victoria, and annual ryegrass tops the list in WA.

In the Northern Territory, the dothideomycete fungus that causes banana freckle disease represents the greatest economic burden, while cats and foxes are the costliest species in the ACT and New South Wales.

The three most expensive species by Australian state/territory.
CJA Bradshaw

Better assessments needed

Our study is one of 19 regional analyzes published today. Because the message about invasive species must reach as many people as possible, the summary of our article has been translated into 24 languages.

This includes Pitjantjatjara, a widely spoken indigenous language.



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


Even the enormous costs we have reported are underestimated. This is because we have not yet surveyed all the places where these species are found, and there is a lack of standardized reporting by management authorities and other agencies.

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

Development better methods Estimating the environmental impacts of invasive species and the benefits of management actions will allow us to use limited resources more efficiently.

Phytophthora cinnamomi, a widespread, but largely unquantified, fungal pathogen.
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A constant threat

The fall armyworm, a major crop pest.
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Many species harmful to Agriculture and the environment have not yet reached our shores.

The recent arrival in Australia of the fall armyworm, a major agricultural pest, reminds us of how invasive species continue their broadcast here and elsewhere.

In addition to economic damage, invasive species also bring intangible costs we still need to measure properly. These include the true extent of ecological damage, human health consequences, erosion of ecosystem services and loss of cultural values.

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


The authors acknowledge the traditional owners of the lands on which they conducted this research.

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