Invasive alien trees are sucking up South Africa’s freshwater and fuelling its wildfires. The invasive polyphagous shot hole borer beetle is killing its trees, while another invasive alien, the water hyacinth, is throttling dams.
Invasive alien species have accelerated the extinction of more than 60% of the world’s plants, animals and insects, according to a major new report on Invasive Alien Species and Their Control, by 86 experts from 49 countries, including SA.
People have introduced alien species to regions where they don’t belong, intentionally or by accident, and nearly a tenth (3,500) of the world’s 37,000 alien species have become harmful invasives.
Now they are a rapidly rising threat to human wellbeing as well as nature, a new assessment report for policymakers by the UN-backed Intergovernmental Platform on Biodiversity and Ecosystem Services finds.
Invasions are like cancer, which can be successfully treated in the early stages.
— Conservationist Dr Guy Preston
“Invasive species are as big a long-term issue as climate change and habitat destruction, destroying our life-support systems and exacerbating poverty, human health challenges and human misery.
“They are equally a disaster for the other species with whom we share this planet,” said SA conservationist Dr Guy Preston, a retired deputy director-general of environmental affairs.
“Invasions are like cancer, which can be successfully treated in the early stages, and potentially terminal if left for too long,” he warned.
The economic cost of invasive aliens, estimated at $423bn (R8bn) a year in 2019, is only the tip of the iceberg, agreed the co-chairs of the report at a recent media launch.
Land is the hardest hit (about 75% of impacts), followed by freshwater (14%) and marine habitats (10%), they found.
Ezemvelo KZN Wildlife scientific manager Dr Sebataolo Rahlao, a co-ordinating lead author, gives the following example of how invasive aliens affect people’s lives: “In SA, municipalities are spending lots of money trying to get rid of gum species in high altitude areas which are devastating water security. That money would have been allocated to other societal issues [like] poverty alleviation and job creation.”
Indigenous peoples and local communities — who are at greater risk of harm from invasives because of their direct dependence on natural resources — contributed to the comprehensive assessment report.
Monica Medina, Wildlife Conservation Society CEO and president, said the new report was a red alert to address all causes of the extinction crisis. “Invasive alien species are adding stress to fragile ecosystems already facing a plethora of other threats,” she said.
The researchers drew on more than 13,000 references and the report — approved by the 143 member states of IPBES in Bonn, Germany, on Saturday — took 4.5 years to complete.
Biological invaders affect native species negatively 85% of the time, and islands are the most vulnerable, said the co-chair of the new report, Prof Anibal Pauchard, of Chile’s Institute of Ecology and Biodiversity.
Preston said: “The invasive mice that are eating alive the seabirds on Marion Island is an example. It is estimated that 19 of the 28 species of seabirds that breed on Marion Island will be driven to local extinction by mice.
“How do we put a price on the value of the largest flying bird, the Wandering Albatross, if invasive rodents are the tipping point that drive it to extinction?”
No community or country, not even Antarctica, can escape the damages of invasive aliens, said Pauchard. “It would be an extremely costly mistake to regard biological invasions only as someone else’s problem.”
Invasive alien species also ratchet up health risks, as flagged by Preston: “Covid is an invasive organism, along with many other human-health diseases — Ebola virus, West Nile virus, cholera, HIV/Aids, Sars, bird flu, swine flu, Dengue ... even influenza.”
Climate change and invasive alien plants interact in a way that’s likely to worsen the effects of both, said report co-chair Prof Helen Roy, from the UK.
She said: “For example, invasive alien plants ... often result in more intense and frequent fires, such as some of the devastating wildfires experienced recently around the world, releasing even more carbon dioxide into the atmosphere.”
Preston flagged invasive species as the “biggest long-term threat” to SA’s water security and biological diversity and the biggest threat in terms of wildfires.
“It is in our own enlightened self-interest that we take real care to avoid moving species into areas in which they did not evolve — and control existing invasive species,” he said.
Would you like to comment on this article?
Sign up (it's quick and free) or sign in now.
Please read our Comment Policy before commenting.