Invaders top threat to Australia's native treasures

Australia must mount an all-out assault on alien invaders if it is to keep bold commitments to ward off new extinctions and protect its unique native treasures, scientists behind a landmark report say. 

The first global assessment of invasive alien species has found they are now one of the top five drivers of biodiversity loss worldwide, alongside land and sea-use change, exploitation of nature, climate change, and pollution.

In Australia they are the No.1 threat, with 3000 or so invaders causing extinctions, suppressing native species, and costing the country an estimated $25 billion a year in agricultural losses and management costs.

Dr Andy Sheppard is the chief research scientist for biosecurity at the CSIRO and co-wrote the report, released by the  Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services in Germany on Monday.

It details how human activities, including international trade and tourism, have helped plants, animals, insects and pathogens invade new places.

More than 37,000 alien species have been introduced to regions and biomes where they don't belong, with more than 3500 becoming invasive - preying on, crowding out and exterminating native species.

Invasive alien species have been a major factor in 60 per cent of recorded plant and animal extinctions worldwide, and the sole driver in 16 per cent of them.

More than 1200 local extinctions have been caused by just 218 invaders.

Globally, economic costs have been conservatively put at $423 billion a year, which is expected to soar, with 200 new species emerging as problems each year, and climate change expected to spur entrenchment in new locations.

"The number of alien species - that is, species introduced to new regions through human activities - has been rising continuously for centuries in all regions globally, but are now increasing at unprecedented rates," Dr Sheppard said.

"Australia’s most impactful invasive alien vertebrates in terms of biodiversity impacts are feral cats on land, and European carp in our rivers. But from a cost to agriculture perspective, European rabbits remain at the top of the list."

As Australia continues its 20-year battle to control and eradiate the red imported fire ant, and stop the spread of the exotic varroa mite threatening the honey and honey-bee pollination industries, Dr Sheppard says Australia must heed the report's key message.

"Prevention is the best, most cost-effective option,'' he said.

"Measures including border biosecurity and strictly enforced import controls have worked in many instances. For example, in Australasia it kept out the brown marmorated stink bug."

But Dr Sheppard said authorities must be ready to respond quickly to inevitable incursions.

"There's a good history of eradication, in particular contexts, especially on islands, but some groups, like plants, are very, very hard to eradicate because they have dormant seed banks," he said.

"Once you can no longer eradicate, there are various containment strategies and control strategies, like biological control that's been very widely used in Australia and New Zealand."

Australia has supported international commitments to protect 30 per cent of its land and waters by 2030, halve the establishment of invasive alien species, and reduce impacts in priority sites.

Report co-author Philip Hulme, a distinguished professor at New Zealand's Lincoln University, says climate change is making once inhospitable places ripe for invasion, and nations must think beyond their own borders, to their regions.

"A problem that's in Australia will come to New Zealand and vice versa, so we should really think about our own region being well funded," he said.

The Invasive Species Council says Australia has lost about 100 native species to extinction since colonisation, most due to invasive species such as cats and foxes.

"It will take long-term, consistent and strategic investments to stop new invasions and deal with existing threats like fire ants and feral deer," biosecurity analyst Lyall Grieve says.

In 2021, a CSIRO report found more than 1250, or eight in 10, of Australia’s land-based threatened species were imperilled by invasive species.

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