Climate change, no one stops the alien species: now they are heading for the Atlantic

They are advancing, favored by climate change. Taking advantage of the tropicalization of our seas. And, more often than not, competing on unequal weapons with native species. But now the last frontier of alien species who colonized the Mediterranean Sea, arriving there over the decades through the Suez Canal, is to cross the Pillars of Hercules. Thus arriving at the Atlantic Ocean. This is the hypothesis of a research coordinated by Cnr-Irbim, the results of which – published on Frontiers in Ecology and the Environment – open new and disturbing scenarios, supported by a set of distribution models developed for ten fish species. “That’s right – he nods Ernesto Azzurroof the Institute for Biological Resources and Marine Biotechnologies of the National Research Council of (CNR-IRBIM), among the authors of the study – These models illustrate how the climate changes are progressively weakening those climatic barriers that had hitherto limited thegeographical expansion of many alien species of the Mediterranean. And we asked ourselves: will these species be able to expand beyond the Strait of Gibraltar? “.

Few doubts, it seems: in the not too distant future, although still undefined, the “aliens” will extend their range of diffusion. Opening an ideal bridge betweenIndo-Pacific Oceanfrom which they come, andAtlantic, separated by millions of years. In a sort of disturbing return to Tethys, the great marine ocean that surrounded the lands that emerged millions of years ago. “We are facing a scenario of biotic homogenization with consequences that are difficult to predict”, he confirms Manuela D’Amen of the Higher Institute for Environmental Protection and Research Rome (Ispra).

And the first species to make the leap could be those that have already reached the westernmost sectors of the Mediterranean, such as spotted puffer fish (Lagocephalus Sceleratus), the flute fish (Fistularia commersonii) and the Golani sardine (Etrumeus golanii). They could be the pioneers of a new and extraordinary geographical expansion that requires researchers to reflect on the consequences of great climate change on biodiversity. And to follow them could be others among the more than one hundred fish species that entered the Mediterranean through the Suez passage76 of which have already established permanent populations, with often harmful effects on native populations, forced to succumb to new “competitors”.

“The opening of the Suez passage in 1896 – explains Azzurro – he re-established contact between the Red Sea and the Mediterranean, giving the green light to hundreds of exotic species, particularly tropical fish, which have managed to invade the Mare Nostrum. And the so-called Lessepsian migration, in deference to the French engineer Ferdinand de Lessepshas forever changed the history of the Mediterranean, with significant ecological and socio-economic impacts “.

Now, however, the question is even more relevant: exotic species, already an integral part of Mediterranean ecosystems, do not intend to stop. And – although their affirmation depends on a series of variables, not least the interaction with native species – the most probable scenario seems to suggest a future characterized by a rapid transformation of marine ecosystems and the services they offer to our societies. Because the species most suited to the current climatic context will tend to assert themselves at the expense of many native species. Our species, which is solely responsible for the current climate change through the emission of greenhouse gases into the atmosphere, is for them a precious albeit unwitting ally. “One more reason – the researchers conclude – to accelerate the implementation of climate policies, as agreed last year Cop26 and as claimed by the international scientific community “.