Staff Reporter
THE Sandpiper Marine Phosphate Project still requires a separately assessed land-based beneficiation component, while a contemporary full-project feasibility assessment must establish current costs, expected realised product prices, financing, market arrangements and the proportion of value that would be retained in Namibia, according to an independent review by fisheries management scientist Dr Carola Kirchner.
Kirchner argues that these economic considerations cannot be separated from the environmental uncertainty surrounding the proposed marine phosphate mining operation, saying that if Namibia is expected to accept certain disturbance of its marine environment while the full ecological consequences remain difficult to quantify, the corresponding national benefits should be substantial, demonstrable and sufficiently durable to justify the risk.
“At present, I do not believe the evidence has demonstrated that,” Kirchner said.
Dr Carola Kirchner, an independent fisheries management scientist, said the debate around marine phosphate mining had increasingly been framed as a choice between claims of unacceptable environmental damage and assertions that scientific studies had established that there would be no significant impact.
Kirchner said the debate around marine phosphate mining had increasingly been framed as a choice between claims of unacceptable environmental damage and assertions that scientific studies had established that there would be no significant impact.
She said neither position adequately reflected the available evidence.
“The environmental impact of physically dredging the seabed is certain,” Kirchner said, while the overall magnitude, duration and cumulative consequences for Namibia’s marine ecosystem and living resources remained uncertain.
The proposed operation would remove seabed sediment and organisms, generate sediment plumes and redeposition, and disturb an ecosystem that supports Namibia’s marine living resources.
Kirchner said the key scientific questions were how extensive those effects would be, how long they would persist and how they could interact over the proposed 20-year life of the mine.
She reviewed the 2022 Environmental and Social Impact Assessment (ESIA) and its specialist studies with particular focus on whether the economic benefits claimed for Namibia would be sufficient to justify the environmental risks and uncertainties.
The assessment shows that dredging would remove seabed habitat and organisms living within it. However, the extent to which the affected ecosystem would recover remains uncertain.
The ESIA refers to recovery observed after offshore diamond mining, but also acknowledges that recolonised communities may differ from the original communities and that recovery could take longer than the approximately 20-year life of the proposed mine, or may not occur within a meaningful period.
The project therefore proposes undredged corridors and residual sediment to support recolonisation, while recommending that benthic baseline information, much of which dates from 2013 and 2014, be updated before dredging begins.
Kirchner said this was appropriate environmental management but also demonstrated that recovery of the Sandpiper seabed had not been established experimentally.
Sediment-plume modelling is among the more substantial studies undertaken for the project. The modelling predicts an individual plume of roughly 1–5 square kilometres at a particular time.
However, the ESIA estimates an overall zone of influence of about 513 square kilometres, with more than 5 mm of fine-sediment deposition over approximately 412 square kilometres and more than 10 cm of deposition over about 151 square kilometres.
Kirchner said the distinction between an individual plume and cumulative deposition over 20 years was important.
“The former may indeed be local and temporary. The latter cannot be described simply by referring to the size of a plume at any one moment,” she said.
The studies also examined the mobilisation of trace metals from disturbed sediment. Elutriation tests generally found that only a small proportion of several metals entered the dissolved phase, suggesting that immediate bioavailability may be limited.
However, Kirchner said toxicity testing had focused largely on surface material, while mining would disturb deeper sediment and ore.
Further toxicity testing using fresh sediment and additional assessment of deeper material were recommended by the specialist review.
She said this did not demonstrate that deeper material was toxic, but meant the available evidence could not establish that it was not.
The ESIA reports approximately 100 parts per million of uranium in the phosphate-bearing sediment and describes the concentration as low and comparable with other mined sedimentary phosphate deposits.
Kirchner said published literature indicated that marine phosphorites were naturally enriched in uranium and that concentrations around 100 ppm did not appear unusually high for marine phosphorite.
However, she said comparisons with other deposits did not by themselves demonstrate ecological safety.
The more important question was what could happen to uranium, thorium and associated radionuclides when phosphate-bearing sediment was dredged, suspended in seawater and redistributed.
The ESIA acknowledges limited information on marine radioactivity and its potential effects on marine organisms and proposes including uranium, thorium and radionuclides in future baseline monitoring.
Kirchner also raised concerns about the availability of the project-specific source cited for the approximately 100 ppm uranium figure, saying she had been unable to obtain the Bateman 2011 report and therefore could not independently assess its sampling design, analytical methods or representativeness.
On hydrogen sulphide, the available evidence was comparatively stronger. A 2014 verification survey covering 26 sites in and around the proposed mining area found indicators suggesting low hydrogen-sulphide flux from the sampled sediments.
However, the specialist assessment said hydrogen sulphide in deeper sediment layers could not be excluded and noted that, if released, the highly toxic substance could affect organisms beyond the immediate dredging area.
The assessment similarly found no clear evidence of anoxia in sampled sediments, although the environment is naturally oxygen-poor. It considered the risk of nutrient-driven phytoplankton blooms and subsequent oxygen depletion low because pore-water volumes were small and dilution was expected to be substantial.
Kirchner said these findings supported a relatively low expected risk but also showed that some uncertainties would only be resolved through additional baseline work and monitoring.
She identified potential food-web effects as another important limitation.
The northern Benguela ecosystem is interconnected, with benthic and pelagic components supporting species that transfer energy through the food web. Kirchner noted that bearded gobies, for example, consume jellyfish and seabed-associated material and are prey for fish, seabirds and seals.
The fisheries specialist assessment acknowledges that indirect food-web effects and trophic cascades are possible, but describes them as possible rather than verifiable.
Kirchner said no Sandpiper-specific trophic study appeared to have quantified predator-prey relationships, benthic-pelagic coupling or changes in energy transfer following dredging.
She said this did not prove that a major trophic cascade would occur, but meant conclusions about limited food-web effects were largely based on ecological inference rather than measurements from the project area.
The ESIA also concludes that the proposed mining area is not an identified important spawning or nursery ground for the principal commercial hake and monk fisheries.
Kirchner said, however, that finding no evidence that the area was uniquely important for spawning was not the same as demonstrating that disturbance there would be biologically irrelevant.
Fish could respond to noise, increased suspended sediment, altered feeding conditions and changes in prey availability through avoidance or redistribution.
She said such behavioural responses had not been directly tested at Sandpiper and that conclusions therefore relied substantially on species distributions, existing literature, comparable activities and assumptions about the spatial extent of disturbance.
Kirchner further pointed to changes in Namibia’s small-pelagic fisheries information since the ESIA was prepared.
The ESIA relies substantially on fisheries information from a period when Namibia’s pilchard stock was severely depleted. A 2014 verification survey also used bottom-trawl gear and was not designed to sample sardine, anchovy and other small pelagic species.
The 2025 Ministry of Fisheries and Marine Resources/Namibian Fisheries and Marine Resources Institute small-pelagic survey estimated total sardine biomass at approximately 887,739 tonnes, although with a coefficient of variation of 40%.
Kirchner said the newer information did not demonstrate that phosphate mining would harm the recovering pilchard resource, but showed that older fisheries information should not be regarded as the final assessment of current risk.
She recommended an updated species-specific assessment examining current spatial overlap, sediment-plume exposure and potential food-web effects on recovering small-pelagic resources.
Kirchner also cautioned against equating geographical coexistence between fishing and mining with ecological coexistence.
Although the proposed mining area would occupy only a fraction of Namibia’s exclusive economic zone, fish move, eggs and larvae drift, and food webs extend beyond mining boundaries.
“Sediment plumes and deposition do not recognise licence-area lines,” she said.
She added that demonstrating that fishing vessels could operate around a mining area was not the same as demonstrating that ecological processes supporting fisheries would remain unaffected.
The cumulative effects of repeated disturbance over the proposed 20-year mining period also require consideration, according to Kirchner.
The cumulative-impact assessment concludes that Sandpiper’s contribution would be marginal compared with overall activities in Namibia’s exclusive economic zone.
However, Kirchner said ecological importance was not necessarily proportional to the percentage of the EEZ occupied by an activity.
What mattered was which habitats were disturbed, which species used them, how frequently disturbance occurred, how recovery proceeded and whether different effects interacted.
She said the project would combine seabed removal, repeated sediment plumes, cumulative deposition, noise, changes to benthic communities and potential effects on fish and food-web processes over two decades.
The individual effects could each be assessed as low or moderate, she said, while the ecological consequences of their combined and repeated occurrence remained much harder to quantify.
Kirchner also questioned the significance attached to the approximately 27 or 28 specialist studies conducted for the project.
She said the number of reports should not be confused with the number of independent lines of evidence, as some studies were updates of earlier assessments, while others reviewed previous studies or relied on the same baseline information.
Some project-specific documents cited in the ESIA were also not readily publicly obtainable, while some sources cited in the ESIA did not appear in its final reference list, she said.
“The number of reports should not be confused with the number of independent lines of evidence,” Kirchner said.
She stressed that a finding of “no significant impact” should not be interpreted as meaning “no impact”.
An environmental impact assessment significance rating is based on a methodology that considers factors including probability, spatial extent, duration, magnitude and receptor sensitivity.
The ESIA itself identifies adverse effects, including physical removal of benthic habitat, sediment deposition and disturbance, while concluding that these effects are acceptable or manageable.
It also recommends additional baseline studies and monitoring.
Kirchner said the environmental clearance requirement for an updated environmental baseline covering biological communities, radionuclides, water-column and sediment characteristics was an important safeguard.
At the same time, she said, it demonstrated that the environmental knowledge base was not complete.
Kirchner concluded that the Sandpiper debate should not be framed as a choice between environmental catastrophe and environmental harmlessness.
“There is good evidence supporting some of the ESIA’s conclusions,” she said, but pointed to old baseline information, incomplete sampling of some ecosystem components, uncertainty over long-term benthic recovery, limited direct testing of deeper material, unresolved trophic effects and newer fisheries information as areas requiring further consideration.
She said the question ultimately came down to whether the expected national benefits justified the remaining environmental uncertainty.
Kirchner’s earlier review of the project’s economic case found that the available evidence did not establish that Sandpiper was uneconomic, but that the scale and durability of the claimed national benefits remained insufficiently demonstrated.
She said the project still required a separately assessed land-based beneficiation component, while a contemporary full-project feasibility assessment would need to establish current costs, expected realised product prices, financing, market arrangements and the proportion of value retained in Namibia.
“If Namibia is being asked to accept a certain disturbance of its marine environment while the full ecological consequences cannot be quantified with confidence, then the corresponding national benefit should not merely be possible,” Kirchner said.
“It should be overwhelming, demonstrable and sufficiently durable to justify the environmental risk Namibia is being asked to carry.”
At present, she said, the evidence had not demonstrated that.
