The Overlap Between Mining Concessions and Deep-Sea Species Found Nowhere Else

The term "biodiversity hotspot" is often associated with tropical rainforests or coral reefs. The deep ocean has its own equivalent: areas where OBIS records — drawn from thousands of research cruises, remotely operated vehicle deployments, and sediment core studies — reveal unusually high concentrations of documented species, many found nowhere else on Earth.

What Deep-Sea Biodiversity Looks Like

The deep sea — defined as water depths below 200 metres — is the largest living space on Earth by volume. It is also among the least sampled. The species richness that has been documented, despite limited sampling effort, is striking: estimates of total deep-sea species count range from 500,000 to over 10 million, most undescribed.

Biodiversity in the deep ocean clusters around:

Hydrothermal vents — where chemosynthetic bacteria support entire ecosystems independent of sunlight.

Cold seeps — where methane and hydrogen sulphide seeping from seafloor sediments support chemosynthetic communities, with tube worms, ice worms, and rich microbial mats.

Seamounts — underwater mountains that concentrate nutrients in upwelling currents and provide hard substrate for suspension feeders. Seamount summits host high proportions of endemic coral, sponge, and fish species.

Abyssal plains — the vast flat expanses at 4,000–6,000 metres depth that are the primary target for polymetallic nodule mining. Despite their apparently featureless surface, nodule fields host a remarkable diversity of small invertebrates in densities of thousands per square metre.

OBIS: The Ocean Biodiversity Information System

The Ocean Biodiversity Information System is the global open-access repository for marine species occurrence data. As of 2026, OBIS holds over 120 million occurrence records for more than 170,000 species.

In the deep-sea context, OBIS records are disproportionately concentrated in a small number of well-studied locations — the result of decades of research cruises and ROV deployments that are expensive and geographically limited. This creates a significant sampling bias: areas with good OBIS coverage are not necessarily the most biodiverse; they are the most studied.

This means OBIS hotspots underestimate deep-sea biodiversity. A location with zero OBIS records is not a species desert — it is likely unstudied.

IUCN Red List Status in the Deep Sea

The International Union for Conservation of Nature's Red List has assessed fewer than 1% of estimated deep-sea species. Among those assessed:

• Critically Endangered (CR) deep-sea species include several seamount endemics and vent organisms where the known population consists of a single vent field or seamount summit
• Endangered (EN) species include deep-sea corals, some shark species, and several bivalves from vent and seep communities
• Vulnerable (VU) includes a broad range of deep-sea fishes and invertebrates where population data are sparse but declining trends are inferred

Abyssal Claims displays OBIS hotspot data colour-coded by IUCN category, allowing users to filter by threat level and see where the highest-risk species are geographically concentrated relative to ISA mining concessions.

The Sampling Problem and Mining Risk

Recovery timescales. The DISCOL experiment, conducted in the Peru Basin in 1989, physically disturbed 10 km² of nodule field and monitored recovery over 26 years. The 2015 reassessment found that sediment community diversity and abundance had not recovered to pre-disturbance levels after more than a quarter century.

Connectivity. Many abyssal invertebrates have extremely limited larval dispersal — they reproduce locally and cannot recolonise disturbed areas from distant populations.

Unknown unknowns. Because the abyssal plain has been sampled at an infinitesimal fraction of its total area, the number of undescribed species in any given mining zone is genuinely unknown.

Explore Biodiversity Hotspots

Abyssal Claims maps OBIS hotspot records across the deep ocean, with IUCN category filtering. Enable the Biodiversity Hotspots layer and use the filter panel to highlight Critically Endangered and Endangered species records. Overlay Mining Concessions to see where the highest-risk biodiversity concentrations fall within or adjacent to active exploration contracts.

The At-Risk Claims panel in the Legend tab ranks concessions by their overlap with documented endangered species observations — providing a prioritised view of where the conflict between mining and biodiversity is most acute.