From murder hornets to Zika-spreading mosquitos, invasive species are behind 60 per cent of extinctions: report

Non-native species – displaced either by global trade and travel or by climate change – pose “a severe global threat” to local biodiversity, food security as well as public health, a new report has found.

This “underappreciated, underestimated, and often unacknowledged” threat from invasive alien species imposes a global economic cost of more than US$423 billion annually and plays a key role in most plant and animal extinctions, according to a report from the Intergovernmental Platform on Biodiversity and Ecosystem Services published on Monday.

More than 37,000 alien species have been introduced worldwide as a result of human activity – transported from one location to another in ships’ ballast water, for instance. Of these, 3,500 were found to be harmful and invasive as they wreaked havoc on local animal and plant species.

Caribbean false mussels have displaced clams and oysters in the Indian Ocean, while rats and brown snakes are wiping out bird species in the Pacific. European shore crabs have damaged commercial shellfish beds in New England and Canada, the report said.

Mosquito species, migrating further north as the planet warms, have spread malaria, Zika and West Nile Fever to previously unaffected areas, underscoring the public health risk.

The Florida Everglades is teeming with the destructive offspring of erstwhile pets and houseplants, from five-metre (16-foot) Burmese pythons and walking catfish to Old World climbing fern and Brazilian pepper.

In the 19th century, English settlers brought rabbits to New Zealand to hunt and for food. When they multiplied like, well, rabbits, officials imported ferocious little carnivores called stoats to reduce their numbers.

But the stoats went after easier prey: dozens of endemic bird species that were soon decimated, from baby Kiwis to wrybills.

New Zealand and Australia – where a similar bad-to-worse saga involving rabbits unfolded – are “case studies” of how not to control one imported pest with another, said Elaine Murphy, a scientist at New Zealand’s Department of Conservation.

More often, however, invasive species are accidental arrivals, hitching rides in the ballast water of cargo ships, the containers in their holds, or in a tourist’s suitcase.

Murder hornets capable of wiping out entire bee colonies in a single attack are thought to have arrived in the US from Asia as stowaways in freight.

The Mediterranean Sea is full of non-native fish and plants, such as lionfish and killer alga, that journeyed from the Red Sea through the Suez Canal.

Largely due to huge volumes of trade, Europe and North America have the world’s largest concentrations of invasive species, defined as those that are non-native and cause harm and have relocated due to human activity, the IPBES report showed.

As global warming continues to make new areas habitable for alien species and international trade and travel returns to pre-pandemic levels, countries need to bolster border biosecurity, strictly enforce import controls and deploy early detection systems, the report said.

Policymakers also need to double down on the “vital” Kunming-Montreal Global Biodiversity Framework, which aims to curb the invasion of aggressive alien species by at least 50 per cent by 2030.

“Invasive alien species have been a major factor in 60 per cent and the only driver in 16 per cent of global animal and plant extinctions that we have recorded,” said professor Anibal Pauchard, co-chair of the assessment.

Among the alien species, around 6 per cent of plants, 22 per cent of invertebrates, 14 per cent of vertebrates, and 11 per cent of microbes were known to be invasive, the report added, pointing out that indigenous communities and those dependent on nature for livelihoods were most at risk.

The most damaging effect was recorded on islands. The report found that the number of alien plants exceeded native plants on more than 25 per cent of all islands. Land, particularly in forested and cultivated areas, was more vulnerable to these invasive species compared to freshwater and marine habitats.

“It would be an extremely costly mistake to regard biological invasions only as someone else’s problem,” Pauchard said.

While the damage inflicted varies from place to place, “these are risks and challenges with global roots but very local impacts, facing people in every country, from all backgrounds and in every community”.