99.999% of the ocean floor has not been directly observed by humans

It has been said many times: scientists have acquired far more knowledge about space than about the oceans. Yet the ocean floors represent 71% of the Earth's total surface and approximately 93% of them are deep seabeds, that is, located at a depth of more than 200 meters, recalls New Scientist . “While the majority has been mapped using satellites and ship-borne sonar, a tiny fraction has been directly observed,” the British weekly continues. More precisely, 99.999% of the seabed has not been directly observed by humans.

Only 2,130 km ² , one-tenth the size of Belgium, representing less than 0.001% of the deep ocean floor, has actually been explored, according to a new study published in Science Advances . To arrive at this estimate, Katy Croff Bell and her colleagues at the Ocean Discovery League studied data collected during 43,681 deep-sea dives with manned or robotic submersibles. “Visual observations are essential for studying the deep sea,” explains Cosmos . They “provide geographical context for samples collected there, allow for observations of the behaviors and interactions of marine life, and allow for more precise studies of biodiversity,” the authors write.

Thanks to this survey work, oceanographers have created a map of the areas already explored. It “ shows that diving has been concentrated near a few countries, notably the United States, Japan, and New Zealand ,” reports the journal Nature . This represents a major bias in our already very fragmented knowledge of the ocean floor, as Katy Croff Bell explains to New Scientist. She makes a comparison with land:

“If you have only explored North America, Japan and New Zealand, how can you possibly know what the savannah is in Africa and the forest in Southeast Asia?”

In addition, the researchers found that dives were becoming increasingly shallow: those deeper than 2,000 meters accounted for 58.4% of dives in the 1960s, compared to 25.9% in the 2010s. This is despite the fact that three-quarters of the seabed is between 2,000 and 6,000 meters deep.

For the study's lead author, it is essential to launch deep-sea observation campaigns. Because "the limited exploration of such a vast region is becoming a critical issue both scientifically and regulatoryly, given the threats to the deep ocean floor, including both climate change and the potential exploitation of mineral resources," reports Cosmos.