There are numerous unresolved questions that threaten the future of deep-sea mining, including engineering, legal and ecological issues, according to industry experts.

The panel, hosted by Hakai Magazine, said that so many details need to be better understood before deep-sea mining could be pursued.

On the ecological front, scientists need to understand what kind of impact deep-sea mining activity would have on the rest of the world, University of Victoria marine researcher Verena Tunnicliffe said.

"The deep sea is a very stable, very slow system, which just needs a small change in temperature and things get badly put off," Tunnicliffe said during the Deep Sea Mining Demystified webinar.

Deep-sea mining "will also affect the transport of toxins," Tunnicliffe explained. "This is one of the things that many scientists are worried about, the cumulative compounding effects of adding mining onto fishing pressures and climate change pressures."

Many of the scientific concerns are based on the understanding that the ocean stabilises planetary health, and the role of the deep-sea environment is still unclear.

Disturbing these delicate ecosystems could make it harder for the ocean to neutralise human impacts on the planet, Tunnicliffe said, noting that the ocean already absorbs two-thirds of excess carbon dioxide generated by humans.

Impacts from mining activities may also take much longer to be remediated in this unique environment, according to Tunnicliffe.

"Even disrupting a small amount of sediment has changed the behaviour of microbes in sediments for years and years," she said. "Thirty years later, microbial populations have not come back from just turning over the sediments" in experiments undertaken by German scientists.

Tunnicliffe also expressed scepticism at claims that deep-sea mining would only target areas with low levels of biodiversity.

In particular, she referred to claims by The Metals Company that sections of the Clarion Clipperton Zone (CCZ) were mostly uninhabited, saying "these areas are not a desert at all."

"We know almost nothing about the abyssal plain, in the specific area where nodules form. There are very low amounts of food coming in, and the nodules themselves form surfaces for organisms, which led to communities that have developed in this area," she said.

Mining complications

On the mining front, identifying mineral-rich areas may be more complicated than expected, Memorial University research chair in deep-sea geology John Jamieson said.

Mineral deposits occur in three types of deposits: hydrothermal vents, which can be rich in copper zinc, gold, and silver; cobalt-rich crusts, which can contain manganese, cobalt, copper, and nickel; and polymetallic nodules, which are potato-sized balls lying on the bottom of the ocean which contain copper, gold, zinc, and silver, among other metals.

While the location of polymetallic nodules has been identified in the CCZ, the location of hydrothermal vents is difficult to pinpoint, Jamieson said, and there may be severe regulatory challenges to come.

"The way it looks like regulations [on deep-sea mining] is evolving, it will likely be the case that there will be a ban on exploiting active vents," he said. "That leaves the inactive vents. The problem is - the way we find deposits on the seafloor is by hunting out the hydrothermal plume which spreads out for kilometres. If there's a dead vent site, there's no hydrothermal plume."

Though scientists have a general idea of how many active vents exist on the ocean floor, there is no such clarity on the number of dead vents, Jamieson said.

"It looks like we're going to try to avoid active vents not to destroy ecosystems," he said. "But we don't know where they are, or what lives on them - and there's probably a very specialised ecosystem that's on inactive vents."

The legal angle

Deep-sea mining could happen tomorrow in areas designated as part of national territory, said Klaas Willaert, a law professor at the University of Ghent who specialises in the international maritime regulations.

"A number of countries have quite advanced legislation in place" to kick-start deep-sea mining, he said.

International waters, which extend from the limits of the continental shelf surrounding national borders, are governed by the International Seabed Authority (ISA). The ISA is currently engaged in forming regulations on deep-sea mining.

"We already have regulations on the first two phases of exploration, but rules for exploitation and commercial extraction have not yet been adopted," Willaert said.

The ISA has until 2023 to draft these regulations, because the island nation of Nauru used a procedure to expedite the rules-making process. Nauru sponsors a subsidiary of The Metals Company, which is based in Canada.

"There's a lot of legal uncertainty," Willaert continued.  "The mining code would need to be agreed by June 2023. If this is not the case, we're getting into quite a risky and dangerous situation. Because if there is an application for exploitation activities, the ISA - despite not having published expectations - would need to consider this application for exploitation, and they would need to provisionally approve these expectations."

This throws the question of liability for destructive actions into uncertainty as well, he said.

"There's a lot of uncertainty as to what would happen if there was an accident or major damage to the environment," Willaert said.

For marine researcher Tunnicliffe, deep-sea mining should be a last resort.

"Mankind has a really lousy record of knowing what it's doing and what the results are going to be," she said. "Given the possibility that the deep-sea floor is already contributing to the stability and resilience of the planetary system, we need to get engineers a whole lot of funding to start solving iterative problems to fuel the green economy, without messing up more ecosystems."

Mining companies will soon have the technological know-how to mine the sea floor, Jamieson said.

"If you throw money at engineers, they'll figure it out," he said.

"There are a zillion reasons not to mine the sea floor, and fewer reasons to mine the sea floor," Jamieson said. "We still know so little. We have so much work to do before we can get there."

The full discussion can be found here:  https://youtu.be/LMCAXa5wHeQ?t=159