[spqr0a1]

Unfortunately this sort of mining has long-term impacts on deep sea ecology. It causes substantial loss of species diversity and activity even 26 years later, with this paper estimating recovery will take at least 50 years for a small test patch. https://www.science.org/doi/10.1126/sciadv.aaz5922

[elil17]

Things are a little more complicated than that.

1. Surface mining also has environmental consequences which have to be weighed against the costs of deep sea mining. An area impacted by surface mining can recover in just a decade, but it takes intensive environmental restoration efforts on the part of humans (https://news.ucsc.edu/2021/05/mine-remediation.html). If similar techniques could be developed for deep sea applications, it could reduce the impact of deep sea mining.

2. Researchers are developing robots with advanced propulsion systems which could dramatically reduce the disturbance to sea-floor sediment by mimicking the ways that rays move. (https://interestingengineering.com/culture/new-autonomous-su...) Of course, this is still an active area of research, and it would probably take regulation to force deep sea mining companies to adopt these measures.

3. Nodules are much easier to process, reducing the carbon footprint of deep sea mining vs. surface mining by up to 80% for some metals. (https://www.sciencedirect.com/science/article/pii/S095965262...) This study even tries to account for the secondary effects of mining such as the different impacts that surface and deep sea mining have on carbon sequestered in the ecosystem.

4. Surface mining is more harmful to humans than deep sea mining is because it can leach dangerous chemicals into fresh water supplies. (https://www.usgs.gov/special-topics/water-science-school/sci...)

The effects of deep-sea mining on ocean ecology are much less well understood than the effects of surface mining. While I do think there's good reason to be optimistic about the benefits of deep-sea mining, especially if it can displace surface mining, we shouldn't assume we understand what will happen. I hope the industry continuous to be forced by regulators to move forward cautiously and allow time for environmental studies to take place.

edit: These people are trying to build a deep sea miner that doesn't destroy the seafloor: https://impossiblemetals.com/

[ulrashida]

Sea floor mining is widely ridiculed by both environmental and mining professionals as having more risk than equivalent and better understood efforts on land. At least its close cousin, space mining, has the benefit of taking place off planet. I hope we never see this activity occur commercially in our lifetimes: we barely have gotten a handle on surface and underground mining, why do we run off to scrape the ocean as well?

On 1: The study you have referenced refers to the difficulties of remediating historical abandoned sites, often run under inadequate regulations typically in the 1850's - 1960's. Modern sites are no joke to remediate, but regulators are beginning to pick up on what causes problems to occur and how to ensure these costs are factored into the mining operation. The difficulty of applying effective regulations to international undersea areas is enormous.

On 2: That's great -- lots of things could happen to improve technology in both terrestrial and submarine mining.

On 3: Carbon footprint is not everything when determining the appropriateness of mining. The study cited by the Science article assumes tailings deposition at sea -- mines are not permitted to do this. The article also swans repeatedly over how "high grade" nodules are, but makes no direct reference to their actual grade. The underlying paper suggests a grade of 1.3-1.4 weight percent which is on the bottom end of mid-grade.

On 4: This point can not be concluded without further study. While terrestrial mining has had more historical impacts to humans, this does not allow for comparison on future terrestrial mining vs. a relatively unknown ecosystem impact from aquatic mining. Mining is also not assessed on purely anthropocentric impacts. We've begun to appreciate that systems are interconnected and humans are only one receptor. Enormous caution is required, certainly more than "lower emissions = good".

[orbital-decay]

>Surface mining also has environmental consequences which have to be weighed against the costs of deep sea mining.

What will actually happen is both types will be happily used at the same time, so there's little point in weighting one against the other.

Any other rationalization misses the fact that this is an extremely poorly understood environment (especially if we do compare with surface mining). It's never a good idea to tinker with unknown at scale without understanding it first, let alone commercializing it. Mining history is practically written in mistakes like that.

[cgh]

Point 4 is mostly confined to old abandoned sites, as mentioned in your link. Modern tailings aren’t left to leach acid all over the place, at least not in North American mines. I get that all bets are off in eg Africa, however.

[legulere]

The nodules themself offer a habitat with its hard crust compared to the soft sea-floor. As it takes millennia for the nodules to form this means the habitat for those organisms is basically lost.

[stubish]

I wonder how large a patch we could mine over 50 years, and if it is a meaningful fraction of the ecosystem? The planet is almost covered with deep sea ecology. Plumes and water contamination could significantly increase the affected area, which I'd hope for these studies to be watching for.

(how much affected by drag net fishing might give a ballpark figure)