A precautionary approach of two concurrent nodule mines has the potential to provide a major new revenue stream for the Cook Islands of around US$90 million (NZ$124m) per year, writes Gerald McCormack, Natural Heritage Trust.
In an article concerning the possibility of seabed nodule
mining in the Cook Islands (Cook Islands News, March 27), Te Ipukarea Society
wrote: “We are confident that further research will show that the goods and
services that the ocean provides humanity are actually worth many times more
than what we will get from mining, and for a much longer term.”
In discussing this claim I will focus on deep sea services
because with a precautionary approach to nodule mining the main impacts will be
in the deep sea rather than the surface waters.
The variety and global values of the main deep sea services
are presented in the 2020 Food and Agriculture Organisation (FAO) circular:
‘Economic value of ecosystem services from the deep sea and the areas beyond
national jurisdiction’ (Ottaviani 2020).
Although the circular is focused on the “areas beyond
national jurisdiction” (ABNJ), or International Waters, it also includes the
deep sea within “exclusive economic zones” (EEZs), which makes it inclusive of
the Cook Islands polymetallic nodule fields.
The FAO circular followed the 2005 Millennium Ecosystem
Assessment (MEA) classification of goods and services, which included
non-biological (abiotic) services as well as biological (biotic) services.
In evaluating all MEA ecosystem services the FAO circular concluded
that the non-biological (abiotic) services of fossil fuels and minerals
accounted for 59 per cent of the total value, and the biological (biotic)
services 41 per cent.
Te Ipukarea Society claim is pitting the value of the local
minerals ecosystem service against the other services. To focus on this issue,
I removed minerals (and fossil fuels) from the FAO table and refer to the
remainder as biotic services, although some have non-biological components.
The table shows the FAO estimated value of each service for
2014 along with its percentage of the total. These are global estimates and
below we will estimate the relevant Cook Islands’ contribution to the global
total and compare it to the estimated value of nodule mining.
The oceans cover 361 million square kilometres (km2) or 71
per cent of the earth’s surface. Ninety per cent or 325 million km2 is
designated as deep sea, defined as waters below 200 metres, which is the depth
of the Photosynthesis Zone of the ocean.
The Cook Islands’ EEZ is two million km2 (0.615 per cent of
the global deep sea area). Nodule mining will most likely occur in areas with
nodule densities of more than 10kg/m2 in the central South Penrhyn Basin (SPB).
This nodule-rich habitat has an area of about 300,000km2.
Considering the likely economic constraints, it has been predicted that more
than two concurrent mines would not be economically viable because of depressed
As a basis for discussion, I will use a scenario of two
concurrent mines together removing all the nodules from a nodule-rich area of
about 340 km2/year. This area is about 0.0001 per cent of the global deep sea
The FAO circular concluded that the global deep sea area of
325,000,000km2 provided biotic services with a value of US$177,904 million
(NZ$245,105m) per year. If we assume these biotic services are spread evenly
across the deep sea area, then the biotic services provided by the 340km2 of
our two concurrent mines scenario is 0.0001 per cent of the global value, namely
US$200,000 (NZ$275,547) per year.
In the Trust’s 2016 booklet on a precautionary approach to
nodule mining it was estimated, based on Hein et al. (2015), that each viable
mine would provide a national revenue of about US$45 million (NZ$62m) per year,
based on a 3 per cent royalty for an unprocessed resource plus corporate taxes.
Therefore, our scenario of two concurrent mines would
produce a Cook Islands revenue stream of about US$90 million (NZ$124m) per
year, which is 450 times greater than ecosystem biological services from the
same area valued at US$200,000 per year.
Table of deep sea services and their global values. SUPPLIED/21052818
Without experiments with proposed nodule collectors it is
not possible to estimate plume damage, but as an extreme, let us assume the
area of damage is twice the 2-mine area, which would raise the value of the
biotic services to about US$0.4 million (NZ$0.55m) per year, or 0.5 per cent of
the annual value of the nodules.
To this point in the discussion we have assumed it is an
either-or situation, whereby the Cook Islands cannot harvest the nodules and
also maintain the deep sea ecosystem services. However, my review of articles
on the likely negative impacts of mining on the various biotic services will
show this assumption is false.
The three minor services
Estimating the value of pharmaceutical provisioning service
was very difficult because so few deep sea drugs have been brought to market.
The FAO circular used the six deep sea drugs approved by the US Food and Drug
Administration (FDA) to estimate a value of US$2300 million (NZ$3166m) per year
for global pharmaceutical services.
However, if mining follows the precautionary approach, the
estimated value of pharmaceutical provisioning is irrelevant because there will
be no significant negative impact on this service.
Such an approach would ensure that samples of all animals
and microbes collected during the exploratory phase are made available for
pharmaceutical assessment. In fact, the seabed biological research facilitated
by the possibility of nodule mining will enable the country to gain the full
benefit of this service even if mining never occurs.
Deep sea fisheries made up 5.3 per cent of all global biotic
services. Although our oceanic fishery is small compared to Kiribati and
countries to the west, it is our second most important revenue stream. This
industry could be negatively impacted by the release of nutrient-rich
bottom-water or sediment at the surface.
The Trust has been recommending a precautionary approach
whereby any sediment be returned to near the seabed (below 4000m). Van der
Grient and Drazen (2021) were more conservative in concluding sediment might
need to be released “deeper than 1500m to avoid both the commercial species and
their vertically migrating prey”.
Their conclusion is consistent with the NIWA (2016)
conclusion that nodule mining seabed activities would be very unlikely to
impact oceanic fisheries, because of the great depth and the lack of
upwellings. The Trust continues to promote a near-seabed release of sediment
until more research supports a shallower depth.
The third minor service was research and education. Rather
than a reduction in this service, the greatly increased opportunity for
research and education during the exploratory phase will greatly increase the
value of this service, regardless of whether or not mining ever occurs.
Carbon sequestration service
The FAO circular concluded an immense 90 per cent of the
deep sea biotic services is counteracting climate change by carbon
sequestration, the removal of carbon dioxide from the atmosphere.
In putting a dollar value on deep sea carbon sequestration,
the report used the EU trading value of carbon plus a more nebulous “social”
value of climate impacts. The global valuations were US$4000 million ($5505m)
per year and US$156,000 million ($215,000) per year, respectively. We can use
this FAO global valuation of US$160,000 million ($220,000) per year for carbon
sequestration as a basis for discussion.
Globally, in pre-industrial times the ocean released more
carbon dioxide than it absorbed. However, with the increased burning of fossil
fuels and the making of cement, the concentration of carbon dioxide (CO2) in
the atmosphere has greatly increased and this forces the oceans to absorb more
and more carbon dioxide.
Although the global oceanic absorption of atmospheric CO2 is
immense it is not spread uniformly across the ocean. Takahashi et al. (2009)
developed a global map showing the exchange of carbon dioxide through the ocean
Concerning our area, it showed that around the central South
Penrhyn Basin at ~15°S absorption is equal or slightly above the release of CO2
to the atmosphere. To the south, absorption increased to a maximum of -24 units
around 30-40°S, and to the north CO2 release increased to a Central Pacific
high of +24 around the Equator.
A ship operated by DeepGreen Metals, a company seeking to mine parts of the Pacific ocean seabed for polymetallic nodules. Photo: DeepGreen Metals
We can conclude that the central Cook Islands ocean is not a
significant absorber of atmospheric CO2.
About 80 per cent of the dissolved carbon in the ocean is
held in the deep sea, and although the central Cook Islands absorbs little or
nothing at the surface, our deep sea is still an immense reservoir of dissolved
This carbon dioxide was absorbed into the near-freezing
waters around Antarctica, which Murata et al. (2019) concluded absorbed about
40 percent of all oceanic absorbed CO2. The Antarctic Bottom Water (AABW)
carries that absorbed CO2 down to the seabed and northward through the Cook
Islands to eventually form the bottom water for the whole Pacific.
Nodule mining will not have any significant impact on the
level of dissolved carbon in the kilometre-high AABW as it moves northward over
our seabed nodules. The AABW sequestered carbon will remain sequestered in the
current for hundreds of years.
Orcutt et al. (2020) reported the conclusions of scientists
who met in 2018 to discuss the likely impacts of seabed mining on the services
provided by microbes.
For nodule mining, they concluded that the “proposed mining
of these nodule-bearing sediments and resulting resuspension of particles and
organic matter will have a trivial impact on the ecosystem service of carbon
sequestration” for two reasons: (1) “these sediments contain extremely low
quantities of organic matter (< 0.5 per cent)”; and (2) the organic matter
is “likely to be highly processed” making it not particularly available for
microbial remineralisation, which means it will be redeposited on the seabed
Orcutt’s first reason definitely applies in our situation
because Okamoto (2003) reported 4 percent organic matter in the sediment of
central South Penrhyn Basin. The reason for such “extremely low quantities of
organic matter” is the very low productivity of the surface waters and the very
low level of descending organic matter to the seabed.
In this analysis of carbon sequestration within our area I
have excluded calcium carbonate skeletons which eventually settle on the seabed
to be sequestered as carbonate sediment.
Our abyssal nodules are below the Carbonate Compensation
Depth (CCD), which is the depth by which all descending calcium carbonate is
dissolved. As a result, there is no calcium carbonate sediment associated with
In summary, a precautionary approach in our scenario of two
concurrent nodule mines has the potential to provide a major new revenue stream
for the Cook Islands of around US$90 million ($124m) per year, without any
significant reduction in the deep sea biotic goods and services.
These biotic services, worth about US$400,000 per year
($551,007) for an area twice the size of the two mined areas, would continue to