It's in your nature
Very expensive invasive alien species
Audio 02:38
The Aedes aegypti mosquito, or tiger mosquito.
REUTERS/Paulo Whitaker
By: Florent Guignard Follow
4 mins
Invasive alien species are plants and animals that have become harmful to the ecosystems where they have established themselves.
Harmful to biodiversity, health and the economy.
Their cost has been quantified: 1,300 billion dollars in 50 years.
Advertisement
They are most often stowaways.
The Asian hornet arrived in France in a shipment of Chinese pottery, before colonizing almost the entire country in a few years, to the great misfortune of the bees that this invasive alien species (IAS) attacks.
The tiger mosquito, carrier of tropical diseases such as dengue or chikungunya, arrived in Europe by landing in an Italian port at the bottom of a tire.
These are just two of the 880 invasive alien species recorded worldwide.
Animal or plant species introduced voluntarily or involuntarily in a territory and whose distribution and impact proves to be problematic.
The rise of IAS has accompanied that of globalisation.
These plants, animals and even fungi have benefited from the increased trade and infrastructure built by humans.
The breaker snake
This is the remarkable case of black rats and house mice, followers of cargoes of foodstuffs.
“
In some African or Asian countries, there was a gradual increase in paved roads during the 20th century
,” explains Christophe Diagne, research fellow at IRD, the Institute for Research and Development, in Montpellier, in the south of France.
“
Rodents climb into the trucks in search of food, then are dropped most often involuntarily throughout the journey, to establish year after year stable populations which will favor the invasion inland. .
»
Faced with these IAS, the islands are particularly vulnerable.
This was the case of the island of Guam, American territory in the Pacific Ocean invaded in the last century by the brown tree snake, on the island of Guam, in the Pacific.
“
There were no natural predators on this island and its population was able to slowly develop, until it exploded
,” says Christophe Diagne.
“
He then eradicated a very large part of the native species of birds.
And since he is in a new environment and cannot find the usual trees he used to climb in his original habitat, he began to climb on the electric poles, often causing them to fall, with huge cuts of running from several hours to several days caused by these snakes.
»
Invaders are expensive
Invasive alien species are defined according to their impact on biodiversity, but also human health, agriculture or infrastructure.
And the bill is salty, according to a French study by the IRD, the CNRS and the National Museum of Natural History, published last year in the journal
Nature
.
Between 1970 and 2017, IAS cost $1.288 billion.
A figure which the authors point out is underestimated due to the lack of precise data in certain territories and for certain species.
Nearly 1,300 billion dollars in half a century, which represents an average of 27 billion per year.
But for 2017 alone, the latest available, the bill reached more than 162 billion, more than the GDP of 50 African countries.
The evils are known: destruction of crops or electric cables, spread of parasites or diseases, the impacts of IAS are multiple.
"
These are reservoir species for pathogens
," says Christophe Diagne, the first author of the study.
When they arrive in an environment where the pathogen did not exist, both animal and human populations, which are naive for this species of pathogen, can be affected.
»
green cancer
Conversely, IAS can say thank you to humans, most often directly or indirectly responsible for their proliferation.
In Tahiti, we thought we were doing the right thing by planting a beautiful tree from Latin America,
Miconia calvescens, in a garden.
He did some great damage.
The Tahitians called it "Green Cancer".
"
More than half of the island has been invaded by this tree
," says Christophe Diagne.
“
And since it's a big tree that covers the other plants around it, it blocked the light from reaching those plants.
We started with a simple desire to introduce a very beautiful ornamental plant, to end up with a dramatic consequence since certain local species in Tahiti simply no longer exist.
»
Everywhere biodiversity is collapsing, and it would be more profitable to fight against invasions than against their effects.
Christophe Diagne also pleads for more restrictive legislation as the disease worsens each year.
We could also have spoken of the first invasive species in the world.
The human species, which colonized the planet to destroy it slowly.
"Rabbits, do they b...really like rabbits?" »
In any case, this is what the Australians were able to observe in the 19th century, with the explosion of the population of rabbits imported from Europe, thanks to the mild climate of Australia which allows reproduction all year round.
The damage is considerable for agriculture and the environment.
The Australians then decide to introduce foxes to hunt them.
But they attack marsupials, koalas or kangaroos.
Later, in the 20th century, a disease, myxomatosis, will be introduced.
It is present today on almost the whole planet.
Newsletter
Receive all the international news directly in your mailbox
I subscribe
Follow all the international news by downloading the RFI application
google-play-badge_FR
Wildlife
Flora
Biodiversity
Environment