Title: Assessment of scientific gaps related to the effective environmental management of deep-seabed mining

Authors: Amon et al.

Journal & Year: Marine Policy, 2022

Amon et al. ask two deceptively simple questions: What do we know about the ecosystems where DSM may occur? And what do we know about the impacts of mining and how to manage them?

Their review organizes answers around three mineral-rich habitat types — polymetallic nodules on abyssal plains, polymetallic sulfides at hydrothermal vents, and cobalt-rich ferromanganese crusts on seamounts — and evaluates the level of scientific readiness in each, by region and category.

One of the study’s most informative contributions is its comprehensive matrix of scientific readiness across habitat types and regions.

Presented in Figure 1 (p. 4), this map codes each category (such as bathymetry, species taxonomy, or sediment plume behavior) using a color gradient that ranges from “sufficient for evidence-based management” to “virtually no knowledge.”

Even in better-studied areas like the Clarion-Clipperton Zone (CCZ) many critical elements remain poorly understood.

For instance, although taxonomic surveys have identified thousands of new species, most are known from only a few individuals, and connectivity studies (which determine how species disperse and recolonize) are limited by the scarcity of genetic data and the challenges of tracking larvae in deep currents.

In contrast, regions like the Central Indian Ocean Basin and West Pacific are even less characterized. Baseline biological and ecological knowledge is extremely limited, especially for the smaller, less charismatic but ecologically crucial groups such as meiofauna and microbial communities.

For cobalt-rich crusts on seamounts, which may host long-lived coral and sponge assemblages, the dearth of biological sampling — estimated at under 5% of known seamounts — means that basic assessments of biodiversity, endemism, or ecosystem function remain speculative.

Beyond characterizing what lives in these regions, the study also examines what is known about the likely impacts of mining activities.

The authors identify five main impact categories: direct removal of habitat, sediment plumes, chemical toxicity, physical disturbances like noise and light, and cumulative, long-term effects.

While small-scale test mining has provided valuable insights, large-scale field studies for polymetallic sulfide and cobalt-crust extraction remain limited.

Current impact models often draw on analogs from other marine industries, highlighting the opportunity for DSM to pioneer more targeted, site-specific assessments.

Take sediment plumes, for example. Collector vehicles disturb surface sediments while suctioning nodules, creating clouds of particulate matter that can smother nearby ecosystems or interfere with pelagic species.

Additional plumes are generated when water, separated from mined materials onboard, is discharged back into the ocean.

While plume behavior has been modeled, key variables (discharge depth, turbulence, sediment chemistry) remain unknown or highly site-dependent.

Similar gaps exist for potential noise pollution in the mesopelagic zone and for metal bioaccumulation in fish and other mobile species.

Resilience — defined here as the ability of ecosystems to recover structure and function after disturbance — is another area of concern.

In nodule fields, some species may recolonize sediment within decades, but full restoration, including the regrowth of nodules themselves, could take millions of years.

At active hydrothermal vents, species often exhibit extreme endemism and reliance on chemosynthetic energy sources, making them uniquely vulnerable to disturbance.

In seamounts bearing cobalt-rich crusts, many resident species are long-lived and slow to reproduce, which suggests recovery timelines measured in millennia, not decades.

To supplement their literature review, the authors interviewed 42 global stakeholders, including contractors, scientists, ISA representatives, and civil society groups.

An overwhelming 88% stated that current scientific knowledge is insufficient to make environmentally sound decisions.

The top concern, cited by 71% of respondents, was the lack of comprehensive environmental baselines — not just at the seafloor, but throughout the water column.

This was closely followed by uncertainty about mining’s direct and indirect impacts.

The third most-cited gap was resilience and recovery potential, and the fourth was ecosystem function and services.

While mining proponents often argue that DSM could reduce pressures on terrestrial ecosystems, many stakeholders pointed out that the ocean’s contribution to global climate regulation, nutrient cycling, and biodiversity may be undervalued or poorly understood.

The long-term risks of altering these systems, especially in the face of climate change, remain difficult to quantify.

Rather than framing these uncertainties as an insurmountable barrier, the authors propose a pragmatic solution: a nine-stage roadmap designed to close knowledge gaps while allowing responsible development to proceed.

As outlined in Figure 2 (p. 13), the roadmap begins with defining strategic environmental goals and objectives — something the ISA has only partially achieved in the CCZ through its regional management plan.

The next steps include making contractor-collected data publicly available, synthesizing existing research, developing standardized sampling protocols, and increasing baseline and impact-focused studies.

Of particular interest is the recommendation for “test mining” under controlled conditions. This would allow regulators and scientists to quantify impacts across spatial and temporal scales, validate predictive models, and develop thresholds for acceptable change.

Crucially, the roadmap emphasizes concurrent development: environmental science and mining technology should evolve in tandem, not in isolation. In practice, this would mean that exploration and regulation are interwoven processes, not sequential ones.

The study is candid about the time and resources needed to realize this vision. Even under optimistic scenarios, most respondents estimated a timeframe of 6-20 years to fill critical knowledge gaps, depending on region and resource type.

These durations reflect the logistical difficulty of deep-sea sampling, the slow pace of ecological processes, and the limited number of researchers and vessels capable of operating in such environments.

The authors recommend that each mineral type and geographic zone be treated as its own timeline, with processes running in parallel where feasible.

To fund this effort, the paper suggests a multi-source model involving contractors, states, philanthropic organizations, and multilateral funds.

Contractors, in particular, are seen not just as beneficiaries of this data, but as essential contributors — both financially and scientifically.

Indeed, one of the roadmap’s implicit messages is that corporate environmental leadership could help set DSM apart from legacy extractive industries.

This paper does not argue against deep-seabed mining per se. Instead, it provides a rigorous framework for what responsible mining could look like in one of Earth’s last great wildernesses.

The findings underscore the importance of precaution, transparency, and collaboration.

For proponents of DSM, the message is clear: environmental credibility is not an optional extra — it is the foundation of a viable industry.

By investing now in closing key scientific gaps, stakeholders can ensure that the coming decades of ocean mining are informed by evidence, not assumptions.