For humanity to kick its fossil fuel habit, we’re going to need a lot more wind turbines, solar panels, and batteries. Building all of that green energy infrastructure will likely require billions of tons of metals and minerals, raising the question of where we’re going to get them. One surprising possible answer? The bottom of the sea, where key green energy metals, including nickel, cobalt, and rare earth minerals, can be found in abundance.

But as companies inch closer to actually mining the ocean’s depths, a growing chorus of scientists and environmental advocates are pushing back, warning that such activity could cause irreversible harm to ecosystems we’ve barely begun to understand. Last month, the NGO MiningWatch Canada, along with the Ocean Foundation’s Deep Sea Mining Campaign, published a report calling for a moratorium on regulations that would permit companies to begin mining the Pacific seafloor until the risks are better understood and until all alternatives have been “fully explored and applied.” The International Seabed Authority — a U.N. body with a mandate to oversee resource extraction on the ocean floor — is scheduled to issue draft regulations later this year.

Mining regulations on land “are tailored to our understanding of how the ecosystem works,” said MiningWatch Canada’s Catherine Coumans, who served on the editorial team for the report, which summarizes the findings of more than 250 peer-reviewed studies. In the deep ocean, Coumans said, “we’re creating regulations for an ecosystem that we don’t understand.”

The report focuses specifically on mining “polymetallic nodules,” potato-sized rocks containing manganese, nickel, cobalt, copper, and rare earth minerals that litter a vast expanse of the Pacific seafloor known as the Clarion-Clipperton Zone at depths of 12,000 to 18,000 feet. A number of companies and countries are interested in harvesting these nodules and extracting the metals inside them, which play important roles in green energy technologies, particularly lithium-ion batteries.

But extracting polymetallic nodules from the seabed would come at a price: As the report notes, deep-sea ecosystems are slow to recover, in some cases taking decades to bounce back from a minor disturbance. The removal of polymetallic nodules — which host diverse communities of microbes and marine invertebrates, and serve as a foraging ground for deep-sea fish, many of which are new to science — would permanently alter the environment. The plumes of sediment kicked up by mining activities, meanwhile, could alter light and nutrient availability in the water above the deep sea, with cascading impacts on ocean life, including, potentially, fisheries that many Pacific Island economies rely on.

“The science very comprehensively came down on the side of: This is going to have a huge impact on a large number of species,” Coumans said.

While the report calls for a deep-sea mining moratorium on the grounds that the environmental impacts could be severe, opponents to deep-sea mining are also skeptical that the industry will be necessary to meet the mineral demands of the green energy transition, as proponents often claim. Our mineral needs are unquestionably vast: A recent report by the World Bank found that in order to limit global warming to the Paris Agreement target of 2 degrees C (3.6 degrees F), production of key battery metals including lithium, cobalt, and graphite will likely have to increase by nearly 500 percent by mid-century. But as that report points out, creating new extractive frontiers isn’t our only option for obtaining these minerals.

“My view on this,” said Alex David Rogers, a peer reviewer on the new deep-sea mining report and the science director at the nonprofit REV Ocean, “is we should be looking for more sustainable ways to green our energy system.”

A more sustainable strategy for meeting the mineral demands of the clean energy transition would likely include extending the lifetime of green technologies through additional repair, refurbishing, and reuse. As the World Bank report notes, batteries that no longer have a high enough charge capacity to power an electric car might still be useful for grid energy storage. Old wind turbines, meanwhile, can be refurbished at the end of their lives by replacing worn out components like gearboxes but retaining the original tower structure in order to save on new building materials.

Once green technologies have outlived any useful purpose, we should also be recovering the resources inside them to the fullest extent. While certain metals like aluminum (used in wind turbines and solar panels) are routinely recycled today, others, like rare earth minerals and lithium, almost never are. We’ll need new technologies to efficiently recover these metals from spent batteries and the rare earth magnets found inside wind turbine generators, as well as new collection systems in order to get our e-waste to recycling facilities in the first place.

In the future, we may also develop new clean energy technologies that are less resource-intensive. Tesla, for instance, is reportedly working on cobalt-free batteries to power the next generation of EVs. Alternate wind turbine designs might one day reduce the industry’s reliance on rare earth magnets, or chemists could cook up new recipes making these magnets a bit less “rare” in terms of their composition. However, as Christopher Sheldon, practice manager with the Energy and Extractives Global Practice of the World Bank noted in an email to Grist, “if material substitution were to take place due to changes in sub-technology deployments, the demand for other minerals needed to replace them would most likely rise.”

What’s more, even with new technologies and significantly more recycling, we’re almost certainly going to need more mining, not less, to satisfy the resource demands of the green energy transition. Going forward, the World Bank report emphasizes the need for “climate-smart mining” strategies that minimize deforestation, land degradation, and resource use in the extraction and processing of minerals.

“Resource-rich developing countries should think about developing policy frameworks that encourage the development of greener mining projects,” Sheldon said, noting that such policies could even be integrated into the climate commitments these nations make under the Paris Agreement. The World Bank, Sheldon added, is committed to helping developing nations create policies “to encourage the mining sector to better manage mining waste and integrate more renewable energy into mining operations.”

Deep-sea mining isn’t part of the World Bank’s climate-smart mining initiative, Sheldon said, nor has the organization taken a comprehensive look at the issue. However, he says that the group recommends any nations considering deep-sea mining “proceed with the highest degree of caution to avoid irreversible damage to the ecosystem” and “ensure that appropriate social and environmental safeguards are in place as part of strong governance arrangements for this emerging industry.”

Saleem Ali, a professor of energy and the environment at the University of Delaware, feels that the best way to develop those safeguards is through the International Seabed Authority’s ongoing rulemaking process. Environmental decision-making, he says, “needs to approach the matter with greater nuance than a blanket call for a moratorium.”

“The deep sea ecosystem is indeed precious and this report highlights conservation needs very well,” Ali told Grist in an email, referring to the new MiningWatch Canada report. But he felt the environmental regulations the International Seabed Authority is developing are largely in line with what the new report calls for. “Ultimately, the citizens of small-island developing states who have the most at stake with this effort should have a more pronounced voice as should those communities which are impacted by terrestrial mining for the same minerals.”

Some of those small island states want to see mining move forward. On Monday, officials from the Cook Islands, Nauru, and Tonga issued a letter reaffirming their support for deep-sea mining as a strategy for fighting climate change. All threenations, which are acutely vulnerable to rising sea levels, host companies that have been granted seabed exploration contracts by the International Seabed Authority.

“We are proud that Pacific nations have been leaders in the deep-sea minerals industry from the start,” the letter states. “We are people of the ocean, and we understand better than most how important it is to use its resources in a responsible way.”

In addition to potentially boosting island nations’ economies, would-be deep-sea mining companies are also playing an active role in improving our understanding of the environmental risks of their industry, by funding scientific research in places that few others will.

“We are just at the beginning of understanding ecosystems’ functions on the deep abyssal plain,” deep-sea ecologist Andrew Thaler said, referring to deep-sea plains like the Clarion-Clipperton Zone. “I don’t think anyone would challenge the assertion that we need to learn a lot more. The counterpoint to that argument is the only people doing this research at scale are the folks interested in mining it.”

While Thaler, like Ali, isn’t sold on the idea of a mining moratorium, he says it’s important to ensure that any future deep-sea mining activities proceed slowly, with adaptive management plans and robust monitoring “so that we can make decisions on the fly that will adapt to any perceived new harms as they’re uncovered.”

Benthic ecologist Cindy Van Dover of Duke University echoed that sentiment.

“We do not yet know enough to say that there will be no significant ecological harm,” Dover said in an email to Grist, “but good environmental regulations, impact assessments, monitoring, compliance, and enforcement can help us get to some answers to critical questions.”

At the same time, however, Dover shares one of the key concerns voiced by deep-sea mining opponents: That “we will not be able to fix it once we break it.”

“Assuming we can recognize that we broke the system and caused serious harm, the best solution I can think of is to stop all mining and allow the deep-sea the time it needs to heal itself, ” Dover said. But Dover isn’t optimistic that would happen. “Once an economic and probably strategic engine such as deep-sea mining is in place, I am not sure that there will be the will to stop it.”