“France is among the most affected countries”, recalls Franck Courchamps

More than 37,000 alien species have been introduced, voluntarily or not, by human activities throughout the world. In the batch, more than 3,500 have been scientifically documented as invasive alien species (IAS), which seriously threaten nature and man.

This Monday, the Intergovernmental Science and Policy Platform on Biodiversity and Ecosystem Services (IPBES), to be seen as the IPCC for biodiversity, publishes an inventory of invasive alien species in the world. For four years, 86 experts from 49 countries worked on this report, which reviewed more than 13,000 references.

The observation is clear: these biological invasions are among the five direct factors of biodiversity loss in the world. These invasive alien species “have been a major factor in 60% and the only factor in 16% of the global animal and plant extinctions we have recorded”, point out the authors. And if they harm nature, they also affect humans, causing economic losses and degradation of the quality of life.

France is not immune to the scourge. “Quite the contrary”, slips Franck Courchamp, research director at the CNRS, at the Laboratory of Systematic Ecology and Evolution of the University of Paris-Sud. The ecologist, one of the main authors of this new Ipbes report, responds to 20 minutes.

Was this multiplication of biological invasions, and the associated environmental and economic costs, a foregone conclusion?

What is very interesting with this report is the number of researchers who contributed to it and the number of references on which it was based. The result is an overview, as concise as possible, of these biological invasions, when we are no longer used to looking at specific cases of invasive alien species.

Indeed, this report arrives at impressive figures, both on the multiplication of these invasions and on the impacts linked to them. On the other hand, it is not so surprising. The report clearly mentions the causes of this trend: the acceleration of the global economy, the intensification and widening of changes in the use of land and seas, demographic changes, climate change…

In March 2021, in a study published in Nature, you estimated, with other French researchers, at 1.288 billion dollars the economic losses linked to invasive species between 1970 and 2017. This Monday, the Ipbes estimates the cost at 423 billion dollars each year. How to explain this discrepancy?

There are two reasons. First of all, our article was made from the first version of our database on invasive alien species. This is constantly updated as new studies appear. Thus, since our calculations of March 2021, we have gone from 1.288 billion dollars since 1970 to 2.000 billion today. Moreover, these costs were very small in 1970 before quadrupling every decade since. We then arrive, effectively, at this estimate of 423 billion dollars each year. But we are talking about an estimate. Studies show that it is largely underestimated, as there is a lack of data on this subject. Of the 37,000 known alien species, there are less than 1,000 for which there are studies on the economic cost they generate.

How many exotic species are there in France? How many are invasive?

There are 2,750 exotic species in France, some of which are indeed invasive. In mainland France specifically, one could easily cite at least fifteen which are very problematic: the Asian hornet, the tiger mosquito, the electric ant, the creeping water primrose, the nutria, the Louisiana crayfish, the Japanese knotweed, the rose-ringed parakeet, American mink, leaf ragweed. To my knowledge, however, there is no precise accounting of invasive species on our territory. We have never yet gone so far as to look in detail, out of the 2,750, which are invasive and which are just there without generating major impacts on ecosystems.

On the other hand, with other researchers, we worked on estimating the economic costs of IAS in France. Based on the most reliable data, covering 98 species (27 vertebrates, 14 invertebrates and 55 plants), we estimated them at between 1.2 and 10.6 billion euros over the period 1993-2018, i.e. a cost annual average of between 48 and 420 million euros.

In its report, the Ipbes ranks IAS in the five most important factors of biodiversity loss. What is their place precisely in France?

Ranking these threats does not make sense. It depends on too many parameters. Even on the scale of a country, this hierarchy of threats can change completely, depending on the region, the period, the ecosystem that is taken into account. These rankings are even counter-productive, by pushing the public authorities to concern themselves with one cause more than another.

One certainty, however: invasive alien species are in the top five factors of biodiversity loss in France. Our country is among the most affected by these biological invasions. We are at the crossroads of Europe, we have three coastlines, several borders. And then, France is also one of the world’s largest importers of consumer goods, not to mention the 70 million tourists who come to visit us each year. At the same time, with our overseas territories, we also have one of the greatest biodiversity in the world.

For Ipbes, the threat posed by invasive alien species remains underappreciated and underestimated by countries, with very few having national laws or regulations dealing specifically with the subject. Is France among the good or bad students?

She is not among the best students, in any case. The most effective and least expensive solution to combat biological invasions remains prevention. Admittedly, it’s easier to do on islands, like in Australia or New Zealand. But we could still draw inspiration from what the United States is doing. Their prevention programs are much more advanced than ours, with targeted interceptions of risky shipments at borders, carried out by experts.

But prevention is not everything. At the same time, biosecurity measures must also be implemented. In other words, monitor potential invasions and act as quickly as possible when they are observed, before an exotic species becomes established in a sustainable manner and it becomes impossible to eradicate it. However, we learn too little from our mistakes on this point. A very recent example is that of the electric ant, originating from South America, and the oriental hornet, which have just arrived in the south of France and against which nothing is being done. Like the Argentine ant or the Asian hornet. They have been allowed to establish themselves for several decades, and we can no longer do anything against them today.

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