They trample fragile environments and devastate crops, and now we can put a figure on how much damage invasive species like feral cats and weedy plants are doing to Australia’s bottom line.
- Invasive species cost the Australian economy billions of dollars
- Weedy plants are the most expensive species in South Australia, Victoria and Tasmania
- Early detection and eradication is key to limiting the economic impact
Invasive species have cost the Australian economy $390 billion in just the past 60 years, according to research published in the journal NeoBiota today.
Feral cats are the most costly individual species, which is mostly down to population control, coming in at over $13.5 billion.
But it’s weedy plants that are the most expensive group on the list, according to author Corey Bradshaw from Flinders University.
“That’s not a surprise because they affect the agriculture industry mostly, and so there’s a big economic incentive to assess how many are out there and report those costs,” Professor Bradshaw said.
The total cost of an invasive species was determined by looking at things like crop or livestock damage; the combined cost of management including eradication; and even human salaries.
But although staggering, Professor Bradshaw said the $390 billion figure is probably an underestimation.
“Because it’s really difficult to put monetary costs on things like ecological function, or even bushfire risk.”
Weedy plants cost economy over $200b
With ryegrass, parthenium and ragwort highest on the list, invasive plants have cost the economy over $200 billion since the 1960s.
In Tasmania, the pasture weed ragwort accounts for over 50 per cent of the state’s invasive species costs.
And in South Australia and Victoria, common heliotrope is the costliest of all invasive species.
“All of those costs are borne by the farmers, which then pass on to consumers, and in taxpayer money through government investment,” Professor Bradshaw said.
But despite this research being the most up to date and expansive assessment of the total cost of invasive species, Professor Bradshaw acknowledges there are some glaring omissions.
“We couldn’t find a single economic assessment for root rot — that widespread and very economically damaging species to both agricultural and ecosystems,” he said.
“People often focus on the ecological damage, but they don’t provide the economic costs of managing it or trying to eradicate it.”
‘Invest hard in detection and early eradication’
By the time an invasive species is recognised as problematic, it’s usually been there for a while.
“Unless you detect it really early and do something about it, it’s often too late,” Professor Bradshaw said.
“The key is [to] invest hard in detection and early eradication, and you can save yourself billions — literally.”
Putting a value on the less tangible costs of invasive species is also critical, according to Andreas Glanznig, chief executive officer of the Centre for Invasive Species Solutions, who was not involved in the research.
“The other side that’s not as strongly represented in this study, is putting monetary value to environmental and social costs,” Mr Glanznig said.
“What this study really emphasises is that the invasive species are a huge drag on efforts by farmers and industries to lift agricultural productivity.”