Mining the seabed: impacts on marine life remain a concern
An application to mine the seabed in New Zealand’s South Taranaki Bight was withdrawn earlier this year. John Bensalhia reports on developments
Recent findings have highlighted the environmental risks posed by seabed mining. In December 2025, scientists from the Natural History Museum in London, the UK National Oceanography Centre and the University of Gothenburg reported on their research into the effects of seabed mining in a remote area of the Pacific Ocean. The findings were assembled after a comparison of biodiversity two years before and two months after test mining took place.
The study's lead author and PhD student at the Natural History Museum and the University of Southampton, Eva Stewart, explained that the mining machine involved in the work removes around 5cm of sediment, which is home to many animals. The National Oceanography Centre's Dr Guadalupe Bribiesca-Contreras added that a further risk to animals in the area was the pollution caused by mining.
The report made the point that even for a comparatively small-scale study, the findings were serious enough to pose difficulties for large mining companies. Dr Patrick Schröder, senior research fellow at the Environment and Society Centre at think tank Chatham House, commented that current technologies for harvesting are “too damaging to permit large-scale commercial exploration... These were only tests and the impact was significant. If they did that at large scale, it would be even more damaging.”
Earlier this year, Australian company Trans-Tasman Resources withdrew its application to mine the South Taranaki Bight's seabed, after New Zealand's Fast Track expert panel released a draft decision to decline consent. The project would have involved extracting up to around 50 million tonnes of seabed in order to mine approximately five million tonnes of vanadium-rich titanomagnetite concentrate.
The panel declined the application on a number of grounds, including the potential harm done to marine ecosystems and species such as pygmy blue whales and penguins.
The Fast Track panel acknowledged that the mining project could bring both regional and national benefits in terms of employment opportunities, workforce skills development and diversification of the economy. However, when weighed against the environmental consequences of mining, these benefits were “out of proportion.”
Again, one of the biggest concerns raised by the panel was the adverse effect on the local environment, in particular the credible risks posed to Māui dolphins and other marine mammal species, such as kororā/little penguin and fairy prion. Benthic ecosystems would also be in danger from the “geomorphological changes associated with tailings backfill” such as flow liquefaction and related runout.
Another environmental hazard is the noise caused by the mining, as the panel argued that an assessment of the integrated mining vessel and crawler was not enough of a realistic worst-case scenario. The panel was not satisfied that noise levels could be sufficiently controlled during the project, noting another potential source of material harm to sensitive species. Likewise, the panel was unconvinced that sediment plume could be controlled enough during mining. It raised concerns over the uncertainty over the “scale and extent of the sediment plume and deposited sediment resulting from the project, in circumstances where those matters are critical to assessing the project’s effects on the environment and on existing interests.”
Concerns over the natural character of the environment were raised during the review. The panel felt that work from the mining operation would cause too much change to the level of natural character both within the project area and parts of the coastal marine area. Notable changes would arise from seabed morphology (as a result of pits and mounds), water clarity and the continual movement of sediment. The effects of the work carried out were judged by the panel to likely be felt not only for decades, but for centuries.
The panel also discussed the challenges posed to local economies and activities, including adverse effects on Māori commercial and customary fishing and negative impacts on local diving spots.
The outcome was welcomed by Greenpeace Aotearoa, with a spokesperson saying “seabed mining is simply too destructive to go ahead”.
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Image: South Taranaki Bight. Credit: Shutterstock
