Invasive species are costing the world at least €392 billion every year and have become a leading threat to the diversity of life on Earth, according to a UN assessment.
From invasive mice that eat seabird chicks in their nests to non-native grasses that helped fuel and intensify last month’s deadly fires in Hawaii, at least 3,500 harmful invasive species have been recorded globally in every region, spread by human travel and trade. Their impact is destructive for humans and wildlife, sometimes causing extinctions and permanently damaging the healthy functioning of an ecosystem.
Leading scientists say the threat posed by invasive species is under appreciated, underestimated and sometimes unacknowledged, with more than 37,000 alien species now known to be introduced around the world and about 200 establishing themselves each year.
While not all will become invasive, experts say there are significant tools to mitigate their spread and impact, protecting and restoring ecosystems in the process.
“Invasive alien species are a major threat to biodiversity and can cause irreversible damage to nature, including local and global species extinctions, and also threaten human wellbeing,” wrote Prof Helen Roy, Prof Aníbal Pauchard and Prof Peter Stoett, who led the research.
More robust protocols in detecting invasive alien species at point-of-entry to the State, as well as greater awareness and education around problematic species, are paramount in any effort to protect biodiversity in Ireland from significant threats, academics have said.
“Currently Ireland doesn’t have a management plan… we’re really on the back foot,” Prof Frances Lucy, head of the Department of Environmental Science at the Atlantic Technological University said following the publication of the report.
Prof Lucy said that greater efforts were needed to detect possible breaches of biosecurity at Irish borders. “We don’t have proper biosecurity protocol, or biosecurity legislation to keep species out,” she said.
Although it is sometimes difficult to detect how an invasive species end up in Irish ecosystems, checks at border points could prevent problematic species entering the country, according to Collie Ennis, a research associate at Trinity College Dublin’s zoology department.
“We’re an island nation, and we should be watching what’s coming in past our border,” he said.
“Our biosecurity should be stepped up a gear,” he added, advocating for a “proactive, rather than a reactive” approach to invasive species.
Prof Lucy also advocated for an education-based, bottom-up approach to changing the tide on invasive species – including around potential biosecurity breaches.
The assessment, produced by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), the leading UN body on biodiversity science, was produced by 86 experts – including scientists and Indigenous communities – over four and a half years, and was approved by governments this weekend in Bonn.
The findings follow a 2019 report that warned 1m species were at risk of going extinct, threatened by pollution, climate change, invasive species, the direct exploitation of organisms, and land-use change. While invasive species have contributed to 40% of all known animal extinctions, governments requested more research to better understand the problem.
Raising awareness is a “really important aspect of finding solutions” to the impacts of invasive species, according to Prof Laura Meyerson, an author of the UN assessment published on Monday.
“We really rely on people, on citizen science,” Prof Meyerson said, an academic at the University of Rhode Island. “We have to be creative and we have to be appealing, make people want to get involved… The public needs to realise how important they actually are, in being able to manage [invasive species] effectively.”
Dr Cathal Gallagher, the head of research and development at Inland Fisheries Ireland (IFI), said that early intervention is the “ideal situation” in stemming the proliferation of invasive species.
A new steering group, led by the National Biodiversity Data Centre and comprising of various other stakeholders, was established in early 2023 in an effort to formulate a plan in tacking the threat of invasive species, at the “at governmental level, and agency level”.
The top three invasive species include water hyacinth, an aquatic plant native to tropical South America that blocks waterways and damages fisheries, the flowering shrub lantana, and the black rat. Other examples include invasive mosquito species, such as Aedes albopictus and Aedes aegypti, that spread West Nile virus and the Zika virus.
Most invasive species reports were noted in the Americas with 34% of all reports, followed by Europe and Central Asia (31%), the Asia Pacific (25%) and Africa (7%). Three-quarters of reports were in terrestrial ecosystems, mostly woodlands and boreal forests. The authors found that the cost of biological invasions had risen 400% every decade since 1970 and projected at it would continue to soar in years to come.
“One of our real concerns is the loss of the uniqueness of communities of life. As we see more invasive species around the world, we start to see communities looking more similar. Of course, we have concerns about the functioning of those ecosystems and their resilience. Very sadly, the example of Hawaii is one to present as an example of ways in which we’re seeing this worsening and interactions among these global drivers of biodiversity loss,” said Roy.
The expert assessment found that there were a wide range of options to combat the spread and impact of invasive species, one of the targets agreed at biodiversity Cop15 last December in Montreal in this decade’s global targets.
Eradication programmes on islands, which are disproportionately affected by the spread of invasive species, have had an 88% success rate, according to the report.
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Examples include Redonda, a mile-long rock that is part of Antigua and Barbuda in the Caribbean, where native vegetation, birds and reptiles burst back into life once invasive black rats and feral goats were removed in 2017, transforming the barren grey rock into a green island once again.
But experts said the emphasis had to move towards the prevention of the spread of invasive species instead of costly eradication programmes.