Why is deep-sea mining bad for the environment?

Sending industrial mining equipment thousands of feet below the surface of the ocean to begin mining the deep sea could have widespread environmental consequences, some of which we can predict, and others we are still working to understand. 

For this reason, more than 30 countries have agreed to a ban, moratorium or precautionary pause on deep sea mining. However, an impasse over the proposed moratorium at the International Seabed Authority, the group tasked by the United Nations to cover policy on deep sea mining, could help mining operations take a step forward. 

Here’s why we will continue to oppose this dangerous mining — taken from a report I co authored with Environment America’s Kelsey Lamp, and Frontier Group’s Tony Dutzik and James Horrox called “We don’t need deep sea mining.” 

Deep sea ecosystems are remote, fragile and slow growing.

The deep ocean seabed is a vibrant, biodiverse place, teeming with complex ecosystems and thousands, possibly millions of species, including deep-sea corals, anemones, sponges and many more that scientists are only now beginning to learn about. 

The extreme conditions and relative inaccessibility of the regions of ocean of most interest for commercial mining have led to a lack of scientific research on this last great wilderness. Hence, the study of the habitats, species and ecosystems that will be impacted by mining is still a developing field. One 2023 study, for example, identified more than 5,000 as-yet-unnamed marine species in the Clarion-Clipperton Zone (CCZ) alone — a remote 1.7 million-square-mile area in the north-central Pacific targeted by mining companies for operations. 

Many of the species likely to be harmed by deep-sea mining are long-lived, have slow growth rates and are slow to reproduce. Certain corals, for example, live between 450 and 4,265 years, and some sponges up to 11,000 years – the oldest living creatures known to science. 

Mining operations seek to harvest ferromanganese nodules, which themselves grow only a few millimeters every million years. These nodules support deep-sea life, and since the species that live on them are long-lived and slow to reproduce, mining these areas will mean the ecosystems they support, and in particular the sessile organisms that live on the nodules themselves, will be effectively gone forever.

Photo by NOAA | Public Domain

Test mining showed long-term damage to the ecosystem. 

A study by the German project Disturbance and Recolonization (DISCOL) plowed a several-square kilometer area of ocean floor in the Pacific with experimental mining equipment and monitored its recovery. The study found that it took seven years for the area to recover to the same density of bottom life as before, but even then, some species had permanently disappeared. Looking at just one site, moreover, this study does not account for the fact that the damage would be multiplied by the cumulative impacts of multiple mining operations.

The first seabed mining test site, on the Blake Plateau off the Carolina coast in the Atlantic, offers an even gimmer warning. Despite the fact that experimental mining occurred in 1970, more than 50 years ago, the signs of mining were quite visible when scientists revisited the site earlier this year. In fact, John Hocevar, the longtime director of Greenpeace’s oceans campaign, described the findings as showing “No recovery.” 

There are likely negative effects we can’t foresee, and couldn’t fix. 

Not only is the deep ocean home to thousands of as-yet-unnamed marine species, some of which are the slowest growing on earth, there are many aspects of this remote wilderness that scientists know little about. 

For example, scientists recently published new findings that suggest polymetallic nodules could produce oxygen. As my colleagues wrote: “If correct, it means there is a whole new source of oxygen on this planet hitherto completely unknown to science. Not only would this revolutionize our understanding of how deep-sea ecosystems work, but it could also be a major milestone in the evolution of our understanding of the origins of life itself.” 

Are we really about to exploit a great wilderness without understanding its importance to the health of the ocean and the whole planet? 

Creating an industrial zone in the deep sea would cause wide-ranging damage throughout the ocean. 

Deep sea mining will clearly disrupt the places where the mining is set to take place — but the impacts would not remain isolated. 

Extraction of ferromanganese nodules from the seabed would likely be carried out by remotely operated vehicles and mining machines equipped with cutting and suction tools to vacuum up nodules from the seafloor. Propelled by caterpillar tracks (like those of tanks or bulldozers) and weighing up to 250 metric tons, these giant machines drive across the seabed, cutting or sucking up the nodules, which are then piped up to the surface with pumps or riser systems and transferred to a surface vessel for processing. This highly destructive process would impact large areas of sensitive habitat.

The impacts of mining will not be limited to the mining sites, however, nor the harms it inflicts confined to the species directly associated with these localized habitats. The process of mining the sea floor generates sediment plumes with the potential to affect sea life well beyond the area being mined. 

1. Plumes of discharge and sediment. Mining machines would create “collector plumes” on and close to the ocean floor. Processing the materials supplied by the mining robots would also create “discharge plumes” pumped back into the ocean (pictured below). These plumes carry harmful substances, sediment and other pollutants, and midwater plumes in particular can potentially carry contaminants significant distances beyond the mining sites.
   
   A 2021 modeling study estimated that a nodule mining operation in the CCZ could discharge 120,000 metric tons of sediment and 61,000 metric tons of fines each year. The midwater plumes created by those discharges could travel more than 1,000 kilometers in every direction from the mining site over the course of a single 20-year mining operation, the study predicts, potentially spreading sediment over an area of several million square kilometers. This sediment would likely contain toxic substances as byproducts of industrial mining, and do serious harm to marine animals – filter feeding organisms in particular – along with other impacts.
2. Changes to ocean temperatures. Streams of warm water discharged during the extraction process can increase the temperature of the surrounding water, and the process of transporting the mined ore to the surface vessel for processing, as well as the processing itself, can warm the upper parts of the water column. Research has suggested that these discharges of warm water in the deep ocean in particular will harm or kill the creatures subjected to them, many of which depend on cold and stable temperatures.
   
3. Noise and light pollution. Introducing noise – from surface vessels, mining vehicles and other machinery – to naturally silent habitats could have serious impacts on species that use sound or echolocation to communicate, hunt prey and evade predators.
   
   Just as deep-sea organisms have evolved to live in the silence of the deep ocean, so too have many evolved to live in a naturally dark environment. Most of the organisms that live in the deepest parts of the ocean are adapted to the darkness and have reduced visual capacities and highly sensitive vision, and could therefore be easily disturbed by artificial light, such as from collector vehicles and equipment.

Deep-sea mining techniques and their impacts.Photo by U.S. Government Accountability Office | Public Domain

All this damage would be unnecessary: We don’t need to mine the deep sea. 

The growing demand for critical minerals is being used to justify deep-sea mining, including the minerals needed for building batteries, solar panels and other clean energy technologies. 

We don’t need deep-sea mining to transition to clean energy. There are many ways the U.S. and the world can ensure that we have the critical minerals we need without doing lasting damage to the world’s last great wilderness – including by making better use of minerals we have already extracted from the Earth.

In fact, the world currently trashes more of some critical minerals in discarded electronic waste each year than would likely be supplied annually by a proposed ramp-up of deep-sea mining in the central Pacific over the next decade.

We make, use and toss an unconscionable quantity of short-lived gadgets, and addressing that is clearly where we should be focused — with policies like Right to Repair, banning the worst kinds of disposable gadgets, and pushing manufacturers to make longer lasting products.