The tiger mosquito, which again broke its feet in France this summer, is just one example. Of the invasive alien species (IAS), introduced voluntarily or not by human activities, in regions that were not theirs, there are thousands of others. More than 37,000, estimates the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (Ipbes) in a major report published on Monday. From animals to plants, including microbes.
The Ipbes is to be seen as the equivalent of the Intergovernmental Panel on Climate Change (IPCC) but on biodiversity, the erosion of which is the other major environmental crisis in progress. Like its predecessor, its mission is to provide decision-makers with assessments of the state of knowledge on these issues.
Intros at an unprecedented pace
Already in 2019, in its global assessment report, the Ipbes made IAS one of the five main direct drivers of biodiversity loss, alongside changes in land and sea use, direct exploitation species, climate change and pollution. In the process, the 143 member states of Ipbes asked him to dig into this threat of biological invasions in a dedicated report. That of this Monday therefore, written by 86 experts from 49 countries who worked on it for more than four and a half years and relied on more than 13,000 references.
First key message: these introductions of exotic spaces by man are happening today at an unprecedented rate, with 200 new ones listed each year. This in all regions and biomes of the world (even Antarctica). More than 37,000 in total is a conservative estimate, the authors say, because not all of them become invasive, they insist. Only those which are known to have established and spread and which have negative effects on nature and often also on people are considered as such, specifies the Ipbes. All the same, studies make it possible to classify more than 3,500 IAS as “harmful”. In the lot, 1,061 plants (6% of all alien plant species), 1,852 invertebrates (22%), 461 vertebrates (14%) and 141 microbes (11%).
Nature on the front line
water hyacinth is the most widespread. Native to the Amazon basin, it is considered invasive in 74 regions around the world. Lantana Camara, another exotic plant native to South America, and the black rat, native to tropical Asia, complete the podium.
The first affected by these biological invasions is nature itself. These pests attack species, compete with them for access to food resources, and sometimes go so far as to modify the ecosystems where they spread by transforming habitats. The water hyacinth is a perfect example: it covers expanses of water at high speed, thus forming a dense carpet which smothers native species, blocks light in the lower strata, eutrophic the middle… The Ipbes also cites the Nile Perch, a freshwater fish native to Ethiopia and introduced by man to the waters of Lake Victoria, where it has caused the disappearance of hundreds of native species. We could also talk about the zebra mussel, which spreads by clinging to the hulls of ships, thegiant african snail or burmese python qui invade Florida (but not only), red fox which is causing a lot of problems in Australia…
The list is long and the toll is heavy. IAS “have been a major factor in 60% and the only factor in 16% of the global extinctions of animals and plants that we have recorded, indicates Chilean professor Anibal Pauchard, one of the three co-chairs of this report. And at least 218 invasive alien species have been responsible for more than 1,200 local extinctions. The report points to other impacts, such as “biotic homogenization, whereby biological communities around the world become more similar,” or changes in soil and water properties.
A cost of 433 billion dollars per year…
But biodiversity is not the only victim. IAS also affect the services that nature provides to humans and degrade the living conditions of populations, insists the report. Those who depend most directly on nature, such as indigenous peoples and local communities, are the most affected. “More than 2,300 invasive alien species are present on lands managed by indigenous peoples”.
We obviously have in mind the impact on health. Diseases such as malaria, Zika and West Nile fever are, for example, spread by invasive alien mosquito species such as theAedes albopictus (tiger mosquito) and theAedes aegyptii. But IAS also often harm livelihoods and cripple local economies. Here again, the water hyacinth is a good example, which has caused fishing in Lake Victoria to decline, leading to the depletion of tilapia, a fish widely consumed locally. And it is very expensive. “In 2019, the global annual costs of biological invasions were estimated at over $423 billion.” Only 8% of this sum is used to stem these invasions, 92% going to repair the damage.
… And much more in 2050?
More than the gross amount, it is its evolution over the last 50 years that the Ipbes highlights. The costs have at least quadrupled every decade since 1970. A third (37%) of the 37,000 alien species known today have been reported since then as well, another sign that this threat is growing. The acceleration of the global economy, the intensification and widening of changes in the use of land and seas, demographic changes, not to mention climate change leave little doubt to the authors of the report. “Even without the introduction of new invasive species, those already established will continue to expand their range and spread to new countries and new regions,” said Briton Helen Roy, also co-chair of the report. With current trends continuing, the total number of alien species globally is expected to be 36% higher than in 2005.
It is this scenario of the status quo that the Ipbes urges States to avoid at all costs. There is still a long way to go. “The serious global threat posed by invasive alien species is underappreciated, underestimated and often unrecognized”, deplores its experts, with supporting figures. “While 80% of countries have targets related to the management of IAS in their national biodiversity plans, only 17% have national laws or regulations specifically dealing with these issues”, points out the report, which finds that 45% of countries are not investing in the management of biological invasions. The good news is that the solutions exist to stem these invasions. There is even little doubt about the best of them, points out Anibal Pauchard: prevention.