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4 September 2023 Expert commentary

The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES; often described as the IPCC for biodiversity) released its Invasive Alien Species Assessment in Bonn, Germany, on 4 September 2023.

The Invasive Alien Species Assessment represents the first global expert assessment from the 143 IPBES member countries and is the most comprehensive and overarching policy-relevant report on biological invasions in the world to date.

The headline facts are that biological invasions contribute to 60 per cent of all species extinctions and caused $423 billion in losses globally in 2019.

The number of invasive alien species are expected to increase by 36 per cent by 2050, and costs are expected to quadruple every decade.

The three key messages from the report are:

  1. Invasive alien species pose major global threats to nature, economies, food security and human health
  2. With increasing trade and travel, intense land- and sea-use, and climate change, the number and impact of invasive alien species will increase.
  3. We have the track record and the tools and knowledge to address the invasive alien species threats and impacts if we share and grow knowledge and work together across all societies and economies

Dr Andy Sheppard, Chief Research Scientist for Biosecurity at CSIRO, Australia’s national science agency, co-led chapter five of the report, titled ‘Managing biological invasions: approaches, effectiveness, and contraints’.

Dr Sheppard explains why invasive species are of urgent concern, providing key insights from the newly released report with a focus on Australia.

The Summary for Policy Makers of the full report is available on the IPBES website.

All quotes below are available for use by media and attributable to Dr Andy Sheppard, Chief Research Scientist for Biosecurity, CSIRO.

What is the significance of the Invasive Alien Species report?

"Australia has close to 3000 invasive alien species estimated to cost Australia approximately $25 billion every year in losses to agriculture and management costs.

"Invasive alien species are a growing and significant problem around the world. Globally, they are in the top 5 drivers of biodiversity loss, alongside land and sea-use change, direct exploitation of organisms, climate change, and pollution.

“However, in Australia, they are number one – they are the leading cause of biodiversity loss and species extinction."

What does the report tell us?

"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, according to the report.

"Of the more than 37,000 introduced alien species globally over 3,500 have become invasive, causing negative impacts on biodiversity, local ecosystems and species.

"Invasive alien species make up 6 per cent of all alien plants; 22 per cent of alien invertebrates; 14 per cent of alien vertebrates; and 11 per cent of alien microbes, posing major risks to nature and to people.

"People with the greatest direct dependence on nature, such as Indigenous Peoples and local communities, ethnic minorities, migrants, poor rural and urban communities are at even greater risk from invasive species - for example - by being disproportionately impacted by invasive alien vector-borne diseases.

"More than 2,300 invasive alien species are found on lands managed, used and owned by Indigenous Peoples globally impacting their livelihoods, quality of life and cultural heritage; for example, through reducing land access and the high costs of management."

What are examples of invasive alien species of particular concern in Australia?

"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.

"Our most harmful invasive invertebrate is red imported fire ants, because they affect human health, the environment and agriculture. From a purely agriculture perspective fruit flies top the list, however, there remain many exotic species yet to arrive like Khapra beetle that could be equally devastating.

"Most of Australia’s current and likely future weeds are already here with African grasses, prickly acacia, lantana and blackberry top of the list.

"Nationally, the impacts of invasive alien species are primarily in ecosystems heavily converted for agricultural production, such as the wooded grasslands of southeast Australia. With that said, all biomes in Australia are experiencing invasive alien species impacts."

How can we address the issue of invasive alien species?

"Although the spread and impact of invasive alien species are on the rise, damage can successfully be prevented and mitigated through effective management.

"The Assessment provides evidence, tools and options to help governments achieve an ambitious new Convention on Biological Diversity global goal on invasive species.

"A number of approaches can be used to prevent and manage biological invasions.

"Prevention is the best, most cost-effective option. 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 (Halyomorpha halys).

"Eradication programmes are applicable when invasive alien species populations are small and slow-spreading. They have a success rate of 88% when conducted on islands. Eradication of alien plants presents more of a challenge because seeds can lie dormant in the soil.  

"Invasive alien species can be contained and controlled, particularly in closed systems. The successful control of European rabbits in Australia using viruses being a classic example 

"The use of biological control for invasive alien plants and invertebrates has been successful in more than 60% of documented cases. An example of this is the introduction of a rust fungus (Puccinia spegazzinii) to control bitter vine (Mikania micrantha) in the Asia-Pacific region.

"Ecosystem restoration can also improve the results of management of invasive alien species and increase the resistance of ecosystems to future biological invasions."

What needs to happen next to make this a reality?

"Invasive alien species do not respect borders. To achieve success Australia needs to work with other governments in our region and across sectors, NGOs and with Indigenous Peoples and local communities on coordinated action.

"Prevention is better than cure. The Assessment shows it is most cost-effective to invest to reduce the arrival and establishment of invasive alien species. But we can’t stop them all so biosecurity needs effective preparedness and response capability.

"Last year, Australia supported bold commitments in the Kunming-Montreal Global Biodiversity Framework, to prevent species extinction, protect 30 per cent of our unique biomes, reduce the establishment of invasive alien species by at least 50 per cent and reduce the impacts of them in priority sites by 2030.

"If we want to make this goal more achievable, we can’t afford any delay."

What’s an example of an Australian success story in managing an invasive species?

"Australia’s greatest invasive alien species management success has been the successful biological control of European rabbits.

"Since the 1950s Australia have introduced two viruses, both of which we have proven only harm rabbits. This has cut rabbit numbers by a factor of seven and saved Australian agriculture over $70 billion, but still, rabbits are Australia’s number one most costly pest.

"The greatest challenge remains keeping future invasive alien species and diseases out of Australia, and only working in the region and with our trading partners can this be achieved."

Status and trends

  • >37,000: alien species established worldwide
  • 200: new alien species recorded every year
  • >3,500: invasive alien species recorded globally, including 1,061 plants (6% of all alien plant species), 1,852 invertebrates (22%), 461 vertebrates (14%) and 141 microbes (11%)
  • 37%: proportion of known alien species reported since 1970
  • 36%: anticipated increase in alien species by 2050 compared to 2005, under a “business-as-usual” scenario (assumes past trends in drivers of change continue)
  • >35%: proportion of alien freshwater fish in the Mediterranean basin that have arisen from aquaculture


Sea spurge infestation at Darby River. Sea spurge grows along Australia's southern coastline
Rabbits around a small dam in the 1930s. ©  M W Mules, CSIRO
Female cane toads can lay up to 35000 eggs at a time. Photo by Ruchira Somaweera
Feral cats have contributed to the extinction of 27 native species. Photo by Andrew Cooke
Myrtle rust threatens many native trees and shrubs. Photo by Louise Morin
Red fire ant ©  Liliana Ballesteros
European rabbits are the second costliest invasive species.

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