Manganese or polymetallic nodule mining

OPINION: Precautionary principle and best practise should be rigorously applied when dealing with deep sea mining, and this is what local discussion should focus on.

The Te Ipukarea Society (TIS) article “Threats of serious damage” on October 17 was illustrated with the possible negative impacts of the three main types of deep seabed mining: seafloor massive sulphides at hydrothermal vents; cobalt-rich crusts on seamounts; and manganese or polymetallic nodule mining on abyssal plains. This is misleading because the Cook Islands is proposing only one type of seabed mining: manganese or polymetallic nodule mining.

The inclusion of information about other types of mining in very different environments is a distracting red herring. It is unfortunate that the Cook Islands discussion about the possible impacts of nodule mining is being hijacked by what could happen in entirely different situations.

The Saturday article text focused on deep sea mining (DSM) impacts on fisheries. They stated “It is therefore vital that we recognise and fully understand the unavoidable impacts DSM will have on this region and the consequences of those impacts on the rest of the ocean systems, specifically the Cook Islands fisheries.”  And further, the “impact of DSM, not only on the deep seabed but throughout the midwater column, our shallow water shorelines and our beaches.”

TIS makes it very clear that the negative impacts of deep sea mining on our fisheries and beaches are unavoidable. What evidence do they present?

Their only evidence for this conclusion is the 2016 84-page NIWA (National Institute of Water and Atmospheric Research) report to SPC (Pacific Community). In particular, TIS states that the NIWA report “highlighted sediment plumes and ecotoxicity as ‘consistently important, and uncertain, threats to fisheries’ in the Pacific.” Is this seven-word quote from p.79 a fair summary of the NIWA report?

The main conclusion on the effects of nodule mining on fisheries is on p.39. The NIWA authors concluded: “It was felt unlikely that there would be a shift (of fish) caused by seafloor extraction or the extraction plume in the geographic range of any fish, whether tuna, billfish, or bycatch species.” Furthermore, “toxic chemical release would be less in MN (Manganese Nodule) operations, on account of the mining operation being more a dredging of nodules, rather than a physical crushing…”.  And, “In MN operations any release at the seafloor would be too deep for an effect on fisheries, and release through Processing Returns could be more widely dispersed than if done over a seamount.”

The NIWA authors clearly do not conclude that nodule mining will have unavoidable impacts on our fisheries.

A more detailed study of the assessment tables in the NIWA report show that for consequences on a 5-point scale with 0 (zero) Negligible and 1 (one) Minor, nodule mining had 1 (one) for the 14 or 16 concerns. While for risk on a 30-point scale with 1-6 being low risk, nodule mining rated a 1 (one) for the same 14 concerns. The two exceptions concerned the Return of Processing-fines at the surface on the geographic range of tuna, and released toxic chemicals moving into the biological system. Both concerns rated a 1 (one) or minor for consequence, and a 3 (three) or middling-low for risk. It is very clear why NIWA concluded that nodule mining was unlikely to have any negative impact on tuna fisheries.

Nevertheless, the precautionary principle and best practise should be rigorously applied, and this is what local discussion should focus on. While the NIWA report concluded that the negative consequences of Returning Processing-fines at the surface was minor, other evidence makes it clear that disposal of bottom water or sediment at the surface is a matter of concern. Without elaborating the evidence here, I repeat my request that pure deep-bottom water be returned to 500-1000 metres or a depth of similar nutrient content, and sediment be exported or returned to near the seabed.

Although the NIWA assessment indicated that seabed plumes will not affect fisheries they are of concern to seafloor animals. We should take our lead from the senior author of the NIWA 2016 report, Malcolm Clark. He is a NIWA principal scientist leading research in deep-sea habitats and assessing the ecological risk of fishing and mining activities.

One of his research projects involved using a benthic disturber to measure the effects of sediment plumes on the Chatham Rise where there is a proposal to mine phosphorite nodules. This type of research could be done in the Cook Islands under the exploratory phase licences and be available for independent assessment to feed into the Environmental Impact Assessment before any mining is approved.

Written by Gerald McCormack, Director, Cook Islands Natural Heritage Trust | Published in Editorials