Humans have visually documented about 1,470 square miles, or a mere 0.001 per cent, of the deep seafloor, according to a new study. That’s a little larger than the size of Rhode Island, the smallest state in the US.
The report, published recently in the journal Science Advances, arrives as nations debate whether to pursue industrial mining of the seabed for critical minerals.
Some scientists argue that so little is known about the undersea world that more research on the deep seafloor is needed to responsibly move forward with extractive activities. “More information is always beneficial, so we can make more informed and better decisions,” said Katy Croff Bell, a deep ocean explorer who led the study and is founder of the Ocean Discovery League, a group that promotes seafloor exploration.
Learning more about the deep sea is essential for understanding how climate change and human activities are affecting oceans, she said. But the study also highlights the fundamental excitement of exploration that drives many marine scientists. “You can just imagine what’s in the rest of the 99.999 per cent,” Bell said.
The era of visual documentation included in the study began in 1958, with the deep-sea submersible Trieste. The images collected since then let biologists discover new organisms and observe how they interact with one another and their environments, providing insights into ocean ecosystems.
Bringing deep-sea organisms to the surface to study is challenging. Adapted for high pressures, few animals, if any, survive the journey, so photos and videos are crucial. “There are some habitats you can’t sample from a ship,” said Craig McClain, a marine biologist at the University of Louisiana, US, who was not involved in the study. Getting seafloor visuals helps geologists, too. Before the advent of remotely operated undersea vehicles and crewed submersibles, researchers had a more limited approach: drop a big bucket off a ship, drag it along, haul it up and see what was inside.
“They’d just have a jumble of rocks and try to sort it out, with no context,” said Emily Chin, a geologist at the Scripps Institution of Oceanography, US, who was not involved in the new study. “It’s like people who study meteorites trying to understand a process on another planet.” Seeing seafloor rock outcrops in photos and videos has allowed scientists to learn how fundamental Earth processes work. It also helps companies assess potential sites for mining and oil and gas activities.
But getting to the seafloor is expensive, both in funds and time. Exploring one square kilometre of deep seafloor can cost anywhere from $2 million to $20 million, Bell estimated. The dives can take years to prepare for, and just hours to go wrong. And once a dive is underway, it progresses slowly. A rover tethered to a ship has a limited radius of exploration, moving at a crawl, and relocating the ship is tedious. With so many barriers, Bell wanted to know how much seafloor we have seen, and how much is left to explore.
Bell and her collaborators collected more than 43,000 records of deep-sea dives and assessed the photos and videos that have been collected, estimating how much seafloor area the dives documented. All together, they estimated that between 2,130 and 3,823 square kilometres of the deep seafloor have been imaged. That works out to about 0.001 per cent of the entire deep seafloor.
“I knew it was going to be small, but I’m not sure if I expected it to be quite that small,” Bell said. “We’ve been doing this for almost 70 years.”
The study also found that high-income countries led 99.7 per cent of all deep dives, with the US, Japan and New Zealand topping the charts. Most dives were within 200 nautical miles of those three countries. That means that dives are being led by a small group of countries, potentially biasing what is researched, the authors said.
“There are many people around the world that have deep sea expertise,” Bell said. “They just don’t have the tools to be able to do the kind of research and exploration that they want to do.”
NYTNS