'Humans seek cobalt and gold from the oceans — but climate change is a false reason for seabed mining'

Lisa A. Levin is Distinguished Professor of Biological Oceanography and Marine Ecology at the Scripps Institution of Oceanography and the University of California, San Diego. Speaking from COP29 at Baku to Srijana Mitra Das at TE, she explains the risks posed to the deep blue sea:

Lisa Levin is sitting in the middle of a thick throng of scientists, policy makers, leaders and activists in a COP29 hall at Baku, Azerbaijan. Despite the crowds milling about, you can discern both Levin’s expertise in her field — and her empathy for it. She says, ‘I’m a benthic ecologist, a scientist of the depths — I study animal lives, communities and ecosystems on the sea floor. I’m also an oceanographer — my research has extended from intertidal and coastal waters to the deep ocean. I study ecosystems that occur along our long continental margins and deep waters — one of those is oxygenminimum zones which are natural but are now expanding due to climate change.’

Levin’s face takes on a wry expression when she mentions human-induced global warming. ‘The other involves methane seepage. Chemo-sensitive communities develop where methane seeps from the sea floor — this is also being affected by climate change.’

The impacts of global warming, from storms to droughts, are evident on terrestrial Earth . But what is happening in our planet’s deep waters? Levin explains, ‘The deep-sea isn’t well-explored. We know 5% of the ecosystems that live there. To determine what their responses to global warming could be, we use natural gradients that occur, for instance, in oxygen or carbon dioxide — we know this will raise the temperature of the deep-sea floor, which is mostly cold. Animals there have narrow thermal tolerances — they only survive well in a small range of temperatures. When the water warms, the animals try to move to colder water — so, they could travel deeper or change their latitude. Hence, a redistribution of species is expected. Many island nations rely on certain fish, like tuna, as a major source of income — if those move away, they will lose this earning.’

As the crowd bustles about, Levin continues, ‘Warming can also release frozen methane from below the sea surface. It changes the solubility of gas in the ocean — as a result, the ocean loses oxygen or deoxygenates. Warming also makes waters more stratified — vertical mixing is less likely. This means the interior of the ocean loses oxygen because while it is consumed by microbes and animals, it’s not as easily replaced when the waters are more stratified. Both these phenomena are causing a loss of oxygen in the global seas. So far, in the post-industrial era, we’ve lost 2% of this,’ Levin emphasises, ‘But this is not evenly distributed and some areas have lost 30% to 40%.’ What happens in the ocean doesn’t just stay there — Levin adds ocean warming greatly impacts climate on land.

Climate change, of course, is unfurling as we speak but there are other immediate threats the deep-sea faces. Levin has written of the ocean as ‘the last great wilderness’ on Earth but she now emphasises just how much peril confronts these hitherto undisturbed expanses.

‘Right now, the deep-sea is relatively pristine except along our continental margins — there is a lot of bottom fishing, trawling and longlining there. There is great damage already from that — this destroys the sea floor and wrecks any threedimensional structures made by animals. Lost fishing gear traps animals — that is ‘ghost fishing’ — and there’s bycatch. There is a huge amount of debris underwater too — every time I dive, I see cans, plastic bags, bottles, shoes, so many things. These pollutants add to the contamination from land, including chemicals and microplastics dumped into our rivers, winding into the deep-sea.’

Industrial activities centred in these waters also pose hazards. Levin comments, ‘Oil and gas drilling in deep water have been done for decades now. In many places, this is being phased out as fossil fuels are reduced but in others, especially developing countries, this is just beginning as oil companies are planning new activities there. The regular effects of such drilling include noise and seismic impacts which can be very damaging to marine mammals. However, when there is a blow-out of the rig, as happened in the Deepwater Horizon off the Gulf of Mexico in 2010, the effects are devastating,’ Levin says with a firmness both wry and sad. ‘The oil spilled is very toxic to marine life — but so are the dispersants and chemicals used for cleaning up.’

Yet, these perils don’t deter more humans from eyeing these waters. Marine mining is now proposed, literally, as a silver bullet to several ends. Levin outlines, ‘People are seeking to mine ocean nodules and plains for cobalt, nickel and copper, hydrothermal vents for gold and silver, manganese crust on sea mounds for cobalt and nickel and in coastal waters, phosphate mining is sought for fertiliser. All these in volve very destructive practices that will wreck life on the sea floor — they will release sediment plumes and toxins and produce noise, light and vibration disturbing to marine organisms.’

A ferocious irony underpins proposed deep-sea mining. Levin explains. ‘Climate change is being proposed as the motivation for this — these materials go into electric car batteries too and it’s said electrification of the transport system might require them. However, that’s a false claim — battery technology is changing from cobalt and nickel and there are enough supplies on land to provide in the short term. There is also better recycling and reuse of existing metals, so we don’t need to mine so much. Climate change is a false justification for seabed mining,’ Levin emphasises.

She then explains her current endeavour. ‘At COP29, I’m talking about the deep ocean and its role in climate regulation as well as the importance of biodiversity and its connection to climate. We’ve just had a session on balancing deep ocean biodiversity, carbon cycling, resource extraction and resilience. Some climate mitigation activities proposed are actually damaging tobiodiversity in a way that could affect the services species provide for climate regulation. People often treat climate and biodiversity as separate issues — but these are very closely connected, especially in the ocean.’

When asked about her research on invertebrate life histories in the seas, the scientist’s eyes soften and she laughs very gently. She says, ‘I used to work a lot on this, especially larvae and their development and resulting population structures. Invertebrates are wonderful — they have many ways of surviving and reproducing. Their stories tell us about the connectivity of marine populations — and their resilience.’

This strength has been tested so far only by nature. As the human desire to reshape the oceans grows, scientists like Levin are determined to convey what a huge threat that poses — and how much extraordinary life under water could be destroyed.