Scientist warns deep-sea mining could lead to extinction of CNMI’s biodiversity
- Admin
- Dec 5, 2025
- 4 min read
By Mar-Vic Cagurangan
The waters of the Northern Marianas harbor extremely high biodiversity, including endemic species, which will face extinction should seabed mineral extraction take place in the region, a deep-sea scientist at the University of Hawaii in Manoa warns.
“That’s an important consideration,” Dr. Jeffrey Drazen said, noting that the proposed deep-sea mining off the CNMI’s shore would entail a process that might cause long-term damage to the marine habitat.
Drazen discussed his research on the impact of deep-sea mining on ecosystems during a webinar hosted by the environmental group Tano Tasi Yan Todu on Dec. 2.
The group, which comprises scientists, educators and activists, hastily organized the online forum amid the looming deadline
for submission of public comment on the Bureau of Ocean and Energy Management’s call-out for industry interest in deep-sea mining.
The U.S. government is seeking to explore deep-sea mining in federally managed waters offshore the Northern Mariana Islands in line with the Trump administration's bid to facilitate domestic production of critical minerals, ensuring secure supply chains for U.S. defense, infrastructure and energy sectors.
The bureau’s request for information represented the initial steps that could potentially lead to leasing the seabed for mineral exploitation in the CNMI’s outer continental shelf.
Drazen said the emerging industry has set its sights on cobalt or polymetallic crusts atop the seamounts in the Northern Marianas’ exclusive economic zone.
“Mining in this case is not just sucking these loose nodules off the mud, but they're grinding the crust off of the rocks at the seamount, and they're doing that to a depth of about 5 or 10 centimeters,” he said.
“Most of the companies that are interested in doing this right now are targeting the flatter seamounts, which are called guyots, because it will be easier for their mining vehicles to operate in those, but that does not mean that steeper sides won't be mined,” Drazen said.
In terms of engineering, he added, the cobalt or polymetallic crusts are currently the lowest hanging fruit.
“The areas that are being licensed, at least in international waters today for cobalt crust mining, are much smaller than the areas for nodule mining, and we're anticipating that impacts could be something like 250 sq km over 15 years,” Drazen said.
He noted that previous research indicated low resilience in seamount ecosystems, which, like the abyssal plains, also contain nodules on which about half of the diversity lives.
“Do keep in mind nodules do occur on seamounts and could also be mined. Particularly on the deep flanks of those seamounts, you can find nodules,” Drazen said.
“It's important to realize that nodules take millennia to form, so mining them removes potentially a habitat that just will not come back over evolutionary timescales,” he added.
Drazen said the animals living directly on the nodules "will not recover because their habitat will take millions of years to regrow."
Offering a glimpse of the potential environmental risks from crust mining, Drazen cited previous research by a Japanese team that conducted a mining dry-run to study the impact of seamount disturbance.
“We're finding now—and our sampling is sparse—that some of these animals have relatively small ranges,” Drazen said. “So because of the extensive nature of mining in particular areas of the ocean, that then presents an extinction risk for some of this biodiversity.”
During the study, the Japanese team used a grinding vehicle to create tiny tracks, covering about a couple of hundred square meters, Drazen said.
“Some animals were alive between the grinding heads on the collector vehicle. It was definitely not commercial-scale mining," he said. "What they found was that mobile animals in the region seemed to avoid the area even 13 months after the mining activity occurred.”
Grinding activities also released metals and created noise that disturbed marine life.
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“There have been a number of fishing activities on very deep seamounts down to depths of a little over a thousand meters in places like Australia, New Zealand, the North Atlantic, the Hawaiian island chain, and natural recovery from these fishing trawl impacts usually is incomplete after about 20 to 60 years,” Drazen said.
Regarding ecosystem function risks, Drazen explained the impact of mining on dark oxygen production, citing a paper by British scientist Andrew Sweetman, who found that polymetallic nodules actually produce oxygen on the deep-sea floor.
"We normally associate oxygen with the process of photosynthesis in lighted environments, and this was the production of oxygen abiotically, potentially, without the presence of light," Drazen said. "He takes these chambers, he pushes them into the seafloor, and normally all the animals living in those sediments breathe and use up all the oxygen, and the oxygen concentration declines over time."
Drazen said Sweetman's discovery was entirely unexpected, but the result remained uncertain and several questions were left unanswered.
"How much oxygen production is occurring? Under what circumstances? How is this happening? There are lots of unknowns going on with this," Drazen said.
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