The 265 meters of the former French flagship were sent to the bottom by the Brazilian navy on Friday, after a long politico-legal imbroglio. The Foch, which passed under the Brazilian flag in 2000, thus ended its interminable career, more than sixty years after its construction in Saint-Nazaire (44). The grave of the aircraft carrier, whose hull was described as badly degraded by the military, is an abyssal plain 5,000 meters deep. It is located 350 kilometers off the port of Suape, in the east of the country, under waters under Brazilian jurisdiction.
“Exceptional fauna and flora” in the abyss
The potential environmental consequences of such a decision are causing environmental groups to rise up, although it is still difficult to assess them with precision. “By touching the bottom of the ocean, the Foch will have an impact on the local environment, that’s for sure,” says Brest oceanographer Paul Tréguer, founder of the European University Institute of the Sea (IUEM). “We know, thanks to explorations by underwater robot, that the abyssal plains are not a desert but contain exceptional fauna and flora adapted to these extreme conditions. Receiving a load of 25,000 to 30,000 tonnes on your back will generate innumerable mortality among these molluscs, algae and crustaceans”, adds Jacky Bonnemains, spokesperson for the Robin des Bois association.
And what will happen, in the long term, to the asbestos that makes up the insulation of several kilometers of pipes? Of these PCBs that coat the electrical sheaths? Mercury from thousands of neons? Paints with toxic compounds, which cover hectares of partition? Residual hydrocarbons and lubricants? For the Robin des Bois association, “corrosion and erosion will lead to decomposition of the wreck and a slow, pearly release of all the substances that will be ingested by fish and whales for decades. This is a long-term disaster”.
“Less oxygen and therefore less oxidation”
The great depth at which the Foch will erode “is still less unfavorable than if it had been sunk on the continental slope”, nuance Christophe Logette, director of the Center for Documentation, Research and Experimentation on Accidental Pollution of water (Cedre), in Brest. “There is less biodiversity at this depth and also less oxygen. The oxidation action on the aircraft carrier will therefore be more limited,” he continues.
Another subject of debate: asbestos. In the open air, the fibers that we breathe are dangerous, but in water, asbestos refossilizes easily, described scientists from Cedre in 2009. Jacky Bonnemains has the opposite opinion. He explains that with the effects of pressure, corrosion and underwater currents, “it is impossible for asbestos to remain intact”.
The Robins des Bois spokesperson insists that the Foch, as a “toxic boat”, “should have been treated on land under rational conditions”. The aircraft carrier joins, according to him, the wrecks of military ships sunk during the two world wars, among the “time bombs” which release hydrocarbons regularly. Acting on a possible leak from the Foch would also be difficult at this depth, according to Christophe Logette: “By sinking the boat, the damage has been done, if I may say so”.
What impact for Guyana?
Could French Guiana, neighboring Brazil, be affected? “The Foch has become an underwater dump. According to the ascending currents, the toxic residues will go up to the coast of Guyana and the Caribbean islands”, says Jacky Bonnemains. Paul Tréguer relativizes the importance of the impact that the pollution of the Foch could have, on the scale of the ocean. “At a depth of 5,000 meters, where the Foch lies, the volume in which the various pollutants diffuse is immense”.
