A boat crossing a river with water hyacinth (Pontederia crassipes), an invasive alien species in countries such as Egypt, Kenya, South Korea or Mexico.
Photo: © Canva

Danger from invasive alien species underestimated

Invasive alien species are a major threat to biodiversity, playing a key role in 60 per cent of global plant and animal extinctions. Too often ignored until it is too late, invasive alien species are a significant challenge to people in all regions and in every country.

The severe global threat posed by invasive alien species is underappreciated, underestimated and often unacknowledged, the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) warns in September 2023. According to a new report by IPBES, more than 37,000 alien species have been introduced by many human activities to regions and biomes around the world. Over 3,500 of these are harmful invasive alien species, seriously threatening nature, nature’s contributions to people and good quality of life.

Alongside dramatic changes to biodiversity and ecosystems, the global economic cost of invasive alien species exceeded USD 423 billion annually in 2019, with costs having at least quadrupled every decade since 1970.

The experts emphasise that not all alien species become invasive – invasive alien species are the subset of alien species that are known to have become established and spread, which cause negative impacts on nature and often also on people. About  6 per cent of alien plants, 22 per cent of alien invertebrates, 14 per cent of alien vertebrates and 11 per cent of alien microbes are known to be invasive, posing major risks to nature and to people. People with the greatest direct dependence on nature, such as Indigenous Peoples and local communities, are found to be at even greater risk. More than 2,300 invasive alien species are found on lands under the stewardship of Indigenous Peoples – threatening their quality of life and even their cultural identities.

The report shows that 34 per cent of the impacts of biological invasions were reported from the Americas, 31 per cent from Europe and Central Asia, 25 per cent from Asia and the Pacific and about 7 per cent from Africa. Most negative impacts are reported on land (around 75 per cent) – especially in forests, woodlands and cultivated areas – with considerably fewer reported in freshwater (14 per cent) and marine (10 per cent) habitats . Invasive alien species are most damaging on islands, with numbers of alien plants now exceeding the number of native plants on more than 25 per cent of all islands.

The IPBES experts point to the generally insufficient measures in place to tackle these challenges. While 80 per cent of countries have targets related to managing invasive alien species in their national biodiversity plans, only 17 per cent have national laws or regulations specifically addressing these issues. This also increases the risk of invasive alien species for neighbouring countries. The report finds that 45 per cent of all countries do not invest in the management of biological invasions.

Future biological invasions, invasive alien species and their impacts can be prevented through effective management and more integrated approaches, the experts say.

Prevention measures – such as border biosecurity and strictly enforced import controls – are identified by the report as having worked in many instances. Preparedness, early detection and rapid response are shown to be effective at reducing rates of alien species establishment, and to be especially critical for marine and connected water systems. 

Eradication has been successful and cost-effective for some invasive alien species, especially when their populations are small and slow-spreading, in isolated ecosystems such as islands. The successful eradication programmes depend on, amongst other elements, the support and engagement of stakeholders and Indigenous Peoples and local communities, the experts point out.

When eradication is not possible for different reasons, invasive alien species can often be contained and controlled – especially in land-based and closed water systems, as well as in aquaculture. Successful containment can be physical, chemical or biological – although the appropriateness and effectiveness of each option is dependent on the local context. 


Read more on the IPBES website

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