In business, they say the best opportunities are the ones no one has yet seized. And what bigger opportunity than an area of ocean floor half the size of Australia, covered with 21 billion tons of precious metal-rich nodules? The problem is that these “treasures” are located 5000 meters below the surface, in an environment so hostile that we know better than the surface of the Moon. Yet deep-sea mining is presented as a necessity to support the global energy transition. But what happens after we scrape away these nodules?
A team led by professor daniel jones of the National Oceanography Center asked exactly this question, returning to the site of an extraction experiment conducted in 1979. The team's findings, published in Nature, They are surprising: after 44 years, the traces left by the mining machine are still perfectly visible, like fossils of an industrial age imprinted in the abyssal mud.
The Legacy of a Seabed Mining Experiment
The area in question is the Clarion Clipperton Zone (CCZ), a vast abyssal plain in the Pacific between Hawaii and Mexico. At 5000 meters below the surface, where the pressure is 500 times that of the atmosphere, this expanse of mud It hosts billions of tons of potato-sized polymetallic nodules rich in cobalt, copper, manganese and nickel.
In 1979, a 14-metre-long experimental machine began a small mining operation on the seabed and raked the area for four days, collecting nodules and transferring them via a conveyor belt to a crusher. More than four decades later, Professor Jones and his team have returned to examine the results of this experiment.
Forty-four years later, the mine tracks themselves look very similar to when they were first created, with an 8-metre-wide strip of seabed cleared of nodules and two large grooves in the seabed where the machine passed.
What is particularly striking is the unalterability of these scars. In an environment where time flows at a completely different pace than ours, almost half a century has not been enough to erase human traces.
A fragile and interconnected ecosystem
The associate professor Adriana Dutkiewicz of the University of Sydney, who was not involved in the research, highlights the exceptionality of these deep-sea ecosystems. Polymetallic nodules are not simple stones; they are finite resources that grow by accretion around a nucleus at an incredibly slow rate: approximately 0,001 millimeters every 1000 years.
This means that Many of the nodules on the ocean floor are between 12 and 15 million years old. I smile when I think that while we humans consider anything a few thousand years old to be “ancient,” we are now contemplating mass-collecting objects that began forming when our ancestors were just coming down from the trees.
But there is more: these nodules are not simply mineral resources for mining activities in the seabed; they are the habitat of highly specialized biological communities. Dutkiewicz he explains:
Seafloor ecosystems and nodules are inextricably linked.
Among the inhabitants of these extreme environments we find giant unicellular organisms with calcareous shells (called 'foraminifera'), sea cucumbers, fish and many other species that can only live on the hard surfaces of nodules. What do we do? Clean up everything?
Seabed mining, the slow recovery of the deep
Doctor Mark Hartl, member of the research consortium SMARTEX (Seabed Mining and Resilience to Experimental Impact), raises fundamental questions about the effects of ocean floor mining.
There are so many unanswered questions. For example, we know that nodules produce oxygen. If they are removed, will this reduce the amount of oxygen in the deep sea and affect the organisms that live there?
The researchers observed some of the first signs of biological recovery in the study area, but it is important to put these findings into context. The explored area is tiny (0,4 square kilometers) compared to the size of a commercial operation (about 400 square kilometers). Dutkiewicz warns that the recovery rate reported by the authors will be much, much slower after a large-scale commercial operation. And without the nodules, it will be a completely different ecosystem.
And he uses a pretty good analogy to explain the concept:
It's a bit like having a garden. You can weed a large area, and the weeds will come back much more slowly, rather than weeding just a small area, where the weeds grow almost the next day.
The study's co-author, Dr. Adrian Glover of the UK's Natural History Museum, stresses that their findings do not provide a definitive answer on the social acceptability of seabed mining, but they do provide the data needed to make more informed policy decisions.
In a world increasingly hungry for metals to fuel the green transition, we must ask ourselves: are we willing to sacrifice ecosystems millions of years old to satisfy our hunger for resources? And if we do, what scars will we leave on the ocean floor for future generations? Because, as this study shows, in the abyss the wounds remain open for a very, very long time.
