Threats from alien species are increasing


The lionfish (Pterois miles) migrated from the Indian Ocean to the Mediterranean via the Red Sea and is now decimating the local fauna there. © Canva / IPBES

Humans and climate change are disrupting the animal and plant world – literally. Because around 37,000 animal and plant species worldwide have already spread into new areas, as a report by the World Biodiversity Council IPBES now shows. This often has fatal consequences for the local flora and fauna; invasive species play a key role in around 60 percent of species extinctions worldwide. The non-native fauna and flora also causes annual costs of over 392 billion euros.

Humans have been helping to move animals and plants from one region of the world to another for centuries. The alien species reach their new home in the ballast water of ships, on ship hulls or with cargo, are spread through the animal and plant trade or are intentionally introduced, for example as farm animals. Even most of our crops belong to these “neobiota”. However, such species become a problem when they multiply rapidly after their arrival because they have no natural enemies in the new area. They then become an invasive species and can crowd out native species and even drive them to extinction.

200 more alien species every year

The current report of the UN Biodiversity Council (IPBES) underlines how serious – and underestimated – the problem of invasive species is. In it, 85 researchers from 49 countries have compiled the current state of knowledge on the spread and consequences of bioinvaders over a period of four years. According to this, there are now more than 37,000 alien species worldwide and around 200 new ones are added every year. While not all of these have a negative impact on the ecosystems of the newly settled areas, a good 80 percent of them do, as the IPBES report shows.

More than 3,500 animal and plant species are also considered invasive - they are spreading uncontrollably and threatening local biodiversity. These bioinvasors include more than a thousand plants, around 1,850 invertebrates and 461 mammals. “Invasive species are one of the five most serious causes of the global loss of biological diversity,” says co-author Hanno Seebens from the Senckenberg Biodiversity and Climate Research Center Frankfurt. According to the report, invasive species are responsible for around 60 percent of global animal and plant extinctions. “At least 1,200 extinction events of animals and plants can be directly traced back to 218 invasive species,” reports Seebens.

Islands particularly hard hit

Invasive species now exist in almost all regions and biomes of our planet: “34 percent of the effects of biological invasions are found in South and North America, 31 percent in Europe and Central Asia, 25 percent in Asia and the Pacific, and around seven percent came from Africa reported,” reports Seebens. Ecosystems on land are most affected, but native species in freshwater and the ocean are also increasingly being displaced by bioinvasors, including alien crustaceans, molluscs and fish species. The situation is particularly dramatic on many islands: on more than a quarter of them there are already more alien plants than native flora, as the researchers report.

The introduction or introduction of an invasive species can have serious consequences for the affected ecosystems, but also for us humans. For example, the Caribbean mussel (Mytilopsis sallei) causes enormous economic damage to Indian fisheries, the invasive common sand crab (Carcinus maenas) endangers commercially operated mussel beds in New England and invasive mosquito species such as the Asian tiger mosquito Aedes albopictus or Aedes aegyptii transmit diseases such as malaria and Zika and West Nile fever. On some islands, introduced rats and cats have already decimated the native birdlife and brought rare bird species to the brink of extinction.

What to do about it?

According to the IPBES report, the number of invasive species is increasing. In 2050 there could be around 36 percent more alien species than in 2005, according to the scientists' forecast. Because climate change and the increase in global trade and travel are promoting the spread of bioinvaders. There are certainly effective countermeasures: “There are management tools, control options and targeted measures that really work for almost every context and every situation,” explains Seebens.

“Prevention measures – such as strictly enforced import controls – are the best and most cost-effective option, but eradication, containment and control of invasive species are also effective in certain situations,” the researcher continued. But so far, according to the IPBES report, such measures have hardly been implemented. Although 80 percent of countries have embedded targets for dealing with invasive alien species in their national biodiversity plans, only 17 percent of countries also have laws or regulations that address them. 45 percent of all countries do not invest at all in the management of biological invasions.

Source: Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), IPBES Invasive Alien Species Assessment, 2023

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