Alien invaders live among us, cost half a trillion dollars a year

The world’s intergovernmental body for biodiversity and ecosystems says the annual cost of invasive alien species – introduced plants, animals and fungi that have a detrimental effect on native ecosystems – exceeds US$423 billion annually.

That’s more than the price tag attached to the Biden Administration’s student debt forgiveness program for tens of millions of Americans on low and middle incomes and dwarfs the cost of Australia’s forthcoming three-decade-long AUKUS nuclear submarine program.

Invasive species are one of five primary drivers of biodiversity loss, along with changes in land and sea use, species exploitation, climate change and pollution and estimates by the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) found the cost of invasive alien species had quadrupled every decade since 1970.

Around 37,000 alien species are believed to have been introduced into ecosystems through human activities – about 1 in 10 are serious nature threats, and 80% of impacts from all invasives on humans are found to be negative.

This wide-ranging report released overnight in Germany draws on scientific research, government studies and indigenous and local knowledge to quantify the impact of invasives and put forward suggestions for their control.

Among other findings, invasive alien species:

• Are the sole contributor to about 16% of global plant and animal extinctions.
• Contribute to about 60% of other extinctions (either alone or partly contributing to three-quarters of extinctions).
• Largely drive food supply impacts. Diminished food supply accounts for 2 in 3 of all reported impacts from invasive species.
• Are not well-managed on a global scale. 45% of nations have no investment in invasive alien species management.
• Are increasing. Without intervention, there are projected to be 33% more invasive species on the planet in 2050, compared to 2005.

The cost of alien invaders

Globally, alien species shift around the planet thanks to human economic activity. More than any other factor, the use of transportation– by air, sea or land – in trade is deemed a ‘massive’ factor for the introduction of invasive species.

Changes in land or sea use and climate change are moderate to major drivers of invasive spread. Invaders can also help other invaders: introduced hooved and grazing mammals like horses or pigs can trample or destroy native plants while creating disturbances in soil advantageous to the growth of alien flora.

IPBES emphasises that while some drivers might be more impactful than others, none work in isolation. Although some species introductions have been done with the intention of improving the lives of humans, the majority of invasive alien species are detrimental to people. In particular, the most frequently reported impact of invasive alien species is on human food systems.

Of the US$423 billion in global annual costs, 92% are derived from the negative impacts of invasives and the remaining 8% from management initiatives.

One example is the European shore crab (Carcinus maenas). This particularly aggressive species – native to oceans in western Europe – has spread to most continents and is a declared pest in south-eastern Australia, Canada and the US. In 2021, Washington State identified a mind-boggling 5,500% increase in the species in waters around Seattle and the state’s Pacific coastline. In Maine, it’s been blamed for the collapse of wild clam fisheries.

Two years ago, the CSIRO cost the economic impact of invasive species on the Australian economy at $390 billion over the past 60 years; about $25 billion annually. A similar study found the world economy lost US$1.3 trillion to invasive species from 1970-2017.

All assessments on the economic cost of invasive are considered conservative minimums.

“Overall, established pests and weeds and invasive species have cost Australia over the last six decades, $390 billion, so it’s a staggering amount of money,” says Dr Bertie Hennecke, Australia’s chief environmental biosecurity officer.

“Impacts of Australian established invasive species on our landscapes and agriculture are certainly evident and globally, invasive species are one of the main drivers of biodiversity loss. In Australia, it’s one of the number one threats to our vertebrate mammals, for example, such as bilbies and bandicoots and bettongs, and which makes the delivery of this report even more significant to us.”

Control solutions the way forward

Controlling the introduction of invasives is the primary safeguard against economic and ecological costs, but there are options to combat pest species once they’re established too.

Australia is considered to have one of the world’s more effective biosecurity regimes in terms of pathway management where risk introductions are prevented at the border. IPBES recommends effective risk management of invasive alien species before, at and after border checkpoints as a priority for governments.

Species-specific management is also vital, whether through surveillance and detection or eradication and control measures.

Genetic tools are increasingly valuable in combatting invasive species. Environmental DNA analysis is suggested for identifying the presence of invasive species, particularly in aquatic environments. Other genetic technologies – such as gene drives designed to purge feral animals like cats and mice – could also offer a route to governments seeking to control established threats.

“In Australia, we’re world-leading investing in next-generation genetic control technologies that we believe have a huge potential to game change our capacity to manage even quite widespread species,” says Dr Andy Sheppard, CSIRO’s chief research scientist and the coordinating lead author of the IPBES report.

“A lot of work … has demonstrated the capacity in rodents to be able to determine the sex of their progeny, and if we can ‘drive’, for example, male populations of invasive rodents all male, we can more effectively manage these kinds of problems over much wider areas than we currently can using baiting.”

Experts are also calling for greater collaboration and integration across research groups. Distinguished Professor Philip Hulme from Lincoln University (NZ), who also coordinated the report, observed that pooling knowledge across research sectors could support a longer-term “critical mass” of tools to manage invasive threats.

“I think that’s one of the gaps … we need to work more closely together because things slip through the different disciplines,” Hulme says.