Marine Minerals

Marine mining can cause a range of both direct and indirect impacts on the marine environment. Some of these potential impacts are insignificant and/or reversible. But others are potentially significant and could cause irreversible impacts on different components of the marine ecosystem the table below 3452  summarises the full range of potential impacts, which need to be considered, but which will not necessarily result from any individual mining operation. Ways to mitigate these potential effects are discussed in the best practice section.

Potential environmental impact

Benthic impacts
  • Mortality of organisms on the seafloor, and within the seabed, of the direct mining area
  • Loss of sensitive and/or unique habitats if these exist in the area to be directly mined
  • Removal of habitat which underpins marine communities such as through the direct removal of a vent
  • Permanent change in the composition of marine habitats, such as through the removal of hard substrate which species such as cold-water corals require for attachment
  • Smothering of benthic organisms outside the mining area by a sediment plume generated by tailings deposition 

Water column impacts
  • Reduced ability of visual predators to feed due to increased turbidity of seawater
  • Clogging of gills of fish and disruption of filter feeders from high levels of sediment in the water column
  • Reduction in primary productivity through reduced light levels

Marine mammals, seabirds
  • Acoustic impacts from seismic surveys and other production equipment interfering with the way marine mammals locate prey, navigate and communicate
  • Lights causing seabirds to collide with vessels (bird-strike)
  • Increased risk of ship strike
  • Entanglement, injury or drowning in equipment
  • Subsurface activity and lighting potentially interfering with the feeding and reproductive behaviour of marine mammals and seabirds 3458

Disruption of sedimentary and coastal processes
  • Physical changes to the habitat within the mined area
  • Changes to the seabed bathymetry affecting wave patterns, surf breaks, coastal stability and the sediment budget – dependent on vicinity of the mine site to shore, existing processes and the level of mining proposed

Changes to natural character, landscape and amenity
  • Reduction in the ‘naturalness’ of landscapes and the coastal environment due to the introduction of human-made structures, vessels and equipment  
  • Reduction in recreational amenity 

Biosecurity
  • Increased biosecurity risk from introduction of overseas equipment acting as vectors for marine pest species

Other
  • Other ecological impacts resulting from increased light, noise and vibration in the deep ocean environment. These are poorly understood  and dependent upon the spatial scale of the mining and the transient nature of methods used
  • Accidents, such as oil spills and loss of equipment, having adverse impacts on the marine environment
  • Exclusion zones around mining areas disrupting shipping and fishing activity
  • Reduction in fish stocks and spatial displacement of commercial fisheries
  • Disruption of marine traffic routes through exclusion zones around the mining area
  • Degradation of areas and resources of importance to iwi and hapū
  • Destruction or degradation of historic heritage (such as shipwrecks and other marine archaeology)

The following sections describe each type of environmental impact and environmental impacts of particular minerals types in more detail:  

Benthic and water column impacts

Seabed mining inevitably results in significant physical changes to the area that is being mined. The removal of rock or sediment from the seabed, will result in the mortality of all species living on or in the sediment layer, and those living immediately above. Mining may also change the topography of the seabed, and associated hydrodynamics of the area, as well as the composition of the substrate. As a consequence, the original community may be unable to re-establish after mining activity ceases, and be replaced by different species better adapted to the new environment. The significance of this change is dependent on whether the affected species and communities are unusual, rare and/or play a particularly important role in the food web and broader ecosystem functioning.

Deposition of sediment tailings into the marine environment is likely to extend the environmental footprint of the mining activity over a wider area than just the active mine site. Smaller particles may become suspended in a plume, which can travel some distance with ocean currents before settling out. Water-borne sediment is known to be a particular problem for suspension feeding organisms, such as sponges and corals, as the fine particles can clog their filtering apparatus. It can also affect the gills of fish. In addition, such sediment can affect primary productivity, by reducing light levels and thereby the ability of phytoplankton to grow.

When sediment settles, it can smother benthic organisms, and also change the nature of the substrate making it unsuitable for attachment by invertebrates such as corals. The distance and direction the sediment plume will travel, depends on its composition (i.e., grain size) and on oceanographic conditions (e.g., direction, frequency and velocity of currents).

Some coastal and continental shelf areas are used by fish as nursery grounds and feeding areas. Changes to the benthic fauna, following large-scale removal of sand, may result in cumulative impacts higher up the trophic levels, including changes to feeding patterns of fish. 3463  For example, research has shown that juvenile red snapper use sandy shoal areas to feed on small crustaceans commonly found in such material. 3464  In addition, destruction of benthic communities in one area may have implications for those elsewhere. For example, a 2008 report on the Kaipara Harbour raised concerns about the impact that mining may be having on tuatua populations there. In particular, it was thought that the tuatua beds located in and around the sand extraction area may be an important brood-stock for other populations found in the harbour. 3465

These impacts will be sequential, during the long production phase, as adjacent areas are progressively mined. Recovery potential, once mining has ceased, will depend on a range of factors. These include whether the affected species are reliant on the specific features of the habitat which have been removed and whether there are remaining communities in adjacent areas that provide a source for re-colonisation. As many deep-sea species are slow-growing and long-lived, recovery of the benthic communities could take considerable time; in some cases recovery may never occur.

The major challenge for marine mining is the lack of baseline data on what marine species are associated with prospective mining areas. 4567 There is even less understanding of the interactions between different species and trophic levels, the ecological significance of any impacts, and recovery and recolonisation potential.

In a recent decision of TTRL there were a number of hard stone rocky reefs that were identified within the mining area and in close proximity which would be affected by the sediment plume. Concerns were also raised about the ability of shell-fish/filter feeders to survive if there were higher rates of turbidity in the water. 

Marine mammals and fish 

Underwater sound may have acoustic impacts on marine mammals as well as other fauna. 3466  Vessel and mining equipment, including underwater pumps, riser and sinker activity and the vessel-based processing plant, produce varying levels of underwater noise. Generally, such activities are of a short duration. The possible consequences vary from none (affected animals may leave the area) to acute injury (ear drum damage) to serious (death, which depend on noise level encountered, species and habitat. 3467  There may also be cumulative effects from repeated exposure.

Survey and support vessels create a risk of ship strike. The risk will depend on the speeds of the vessel involved, with greater speeds creating greater risk. During surveying, the vessels tend to move slowly (typically operating at around 5 knots) and special flags are flown to warn other vessels of the slow movement. 3468 Subsurface activity and lights may affect marine mammals by interfering with their navigation. 4568  

In the final decision of the Kaipara Harbour sand mining application in 2006 a new condition was inserted relating to increased vessel traffic in the area: “Vessels used by the Consent Holder will, to the extent practicable, travel at a speed that results in no, or minimal, wake when within 300 metres of dolphins”. 3470  In addition an Advice Note was inserted: “Sightings of Maui’s dolphins will be reported by the Consent Holder to the WWF Sightings Network. Where practicable detail on the sighting including GPS coordinates, number of dolphins, and date and time of sighting, will be provided”. 3471  This new condition recognises the impact sand mining activities can have on marine mammals, particularly rare species.

Lights at night on vessels can attract and disturb seabirds and may cause them to collide with the above sea surface structure. Subsurface activity and lights may affect marine mammals by interfering with their navigation. 3472  Other effects include, eco-system effect from a loss of primary productivity and thus a loss of food for some sea-birds. Penguins in the area are also impacted by turbidity in the water and this can lead to an inability to hunt in the area. 

The following table provides some examples of the potential impacts of various activities on marine mammals: 3473

Mining activity

Example of potential impact

Potential level of impact

Boat-towed surveying equipment
  • Behavioural change

Low – for example, no behavioural changes were observed during research work in the Bay of Plenty and Hauraki Gulf 3477

Reconnaissance drilling and sampling
  • Behavioural changes

Proximity dependent

Suction sampling
  • Avoidance and habitat degradation

Proximity dependent

Sonar mapping
  • Habitat degradation Behavioural changes and avoidance of the area

Low 3480

Shallow seismic surveying (low intensity sub-bottom profiling)
  • Behavioural changes
  • Displacement from habitat
  • Changes in vocalisation

Low

Vessel activity
  • Avoidance
  • General habitat degradation
  • Behavioural changes

Potentially high

Active mineral extraction
  • Habitat degradation
  • Avoidance
  • Behavioural responses
  • Potential for indirect effect due to the negative effects on prey

Potentially high

Disruption of sedimentary and coastal processes

Mining may affect the physical environment by altering the bathymetry, which in turn can change the velocities of currents and sedimentary processes. 3485  In relation to sand mining, there are what are known as ‘closed’ systems, with little or no new sand entering the sediment cycle, depending on the size of the system. If sand is removed from these systems, there can be less available to be deposited on the beach, and erosion of the coastline may result as seabed reserves are depleted.

In 2009 the High Court upheld a decision by the Environment Court to reverse the former Auckland Regional Council’s decision to decline consent to McCallum Bros Limited. The consent was to renew dredging consents in the Mangawhai-Pākiri embayment at a rate of 76,000m3 per annum, an increase of 6,000m3 per year above the previous 20 years. The Environment Court had granted consent for 14 years on the basis that the total input of sediment into the system meant that the proposed extraction was not unsustainable. It also concluded that shoreline retreat and erosion could not be attributed to sand extraction over the last 80 years. 3487  This indicates that sand mining activities should be directed to areas where the amount to be extracted is less than new inputs into the system.

In ‘open’ systems new sand is constantly entering the cycle. This can include sand that is being transported along the coast from other areas by marine currents, sand being carried down rivers into the sea, and sand being produced by erosion of nearby coastal cliffs and headlands. In some areas, such as along the west coast of New Zealand, sand may also be transported into coastal areas from further out on the continental shelf. If the amount of sand removed from open systems by mining, is less than the quantity of new sand entering the system from outside sources, coastal erosion is much less likely to occur. Ultimately, to avoid erosion, it is desirable to maintain a positive sediment budget. 

The extraction of sand from the Pouto shoreline in the Northland Region, has occurred for many decades, but has now been abandoned due to possible effects of the mining on shoreline erosion. 3489  Several companies extracted sand from Pouto, particularly during the late 1970s. In 1992, Mt Rex was granted the sole resource consent for the continued extraction of sand, and this expired in 2004 and was not renewed. The resource consent allowed for a maximum of 60,000 m3 to be extracted per year. Monitoring of the Pouto shoreline began in 1990, at the request of the Department of Conservation. The monitoring confirmed that the shoreline was eroding, and therefore that it was not appropriate to continue to extract large quantities of sand immediately adjacent to the shoreline. 3490

Changes to natural landscapes, character and amenity values

Seabed mining can potentially impact on natural landscapes, character and amenity, particularly when it is close to shore or in the foreshore area. This includes unwelcome visual impacts from barges and tugs operating in the marine area, particularly in those areas which are undeveloped and normally little used by vessels. However, the significance of these impacts are directly related to the location of the mining operation, and the level of “naturalness” of the background environment, as highlighted by the Sea-Tow Limited v Auckland Regional Council case discussed below.

In 2006 there were appeals against the former Auckland Regional Council’s decision to refuse consent for the continuing extraction of sand from near-shore areas of Mangawhai-Pākiri Bay by Sea-Tow Limited. Sea-Tow had applied for consents to enable extraction of 27,000 cubic metres of sand per year for 20 years. McCallum Bros applied for consents to enable extraction of 49,000 cubic metres of sand per year for 20 years. Both extractions were to continue activities authorised under previous expired consents and were for discretionary activities. 3492  Parties within the meaning of section 274 of the RMA variously claimed that extraction of sand from a closed system such as this would result in degradation of the natural character of the beach. The Court held that the Hauraki Gulf is not a wilderness waterway. It is frequented by pleasure boats, shipping and other craft. Although a barge and tug passing regularly may not be an attractive view to residents or leisure users of the beach, their presence at sea could not be deemed markedly out of place. It held there were no more than minor adverse visual effects. The Court also held that there would not be any significant adverse effect on natural character. This was largely related to the expectation that the resource would not be depleted because the system was not closed. 3493

Biosecurity

Vessels and mining equipment brought into New Zealand from overseas can act as vectors for non-indigenous pest species. Non-indigenous species are unlikely to survive independently of the vessel in deep offshore waters, but may be transferred to and invade shallow coastal habitats. 3494  This topic is discussed in more detail elsewhere on this website.

Other impacts

There may be other ecological impacts, which are not yet fully understood, resulting from increased light, noise and vibration in the marine environment. 3495  There is also the risk of accidents leading to spillages and loss of equipment within the marine environment.

Mining activities can displace other marine users, such as shipping and commercial fishing, as there are likely to be exclusion zones around the area of mining activity. This is only likely to cause significant problems if large areas are excluded, or if there are multiple mining operations undertaken in one region at the same time. If fishers are excluded from a significant portion of a quota management area, this could increase fishing pressure on the balance of the area. In addition, fish behaviour may be affected, with fish moving away from the area of mining influence. 3496

Mining may negatively impact on areas and resources of importance to Māori. These could include kaimoana areas, wāhi tapu or urupa sites which lie on or under the seabed. This may be through the direct impacts of the mining activity on the seabed, through accelerated coastal erosion caused by the removal of sand from the system, or through the wider impacts of the sediment plume.

The Environment Court heard appeals against the former Auckland Regional Council’s decision to grant replacement consents for sand extraction in the Kaipara Harbour in 2006. The Oruawharo Marae Trust opposed the applications on the grounds that continued sand extraction would have a negative adverse effect on Māori cultural and spiritual values, and that the extraction site was wāhi tapu, among other matters. The Court held that the concerns raised by the Trust, did not of themselves provide a basis for declining or recommending against the granting of consents, and that monitoring and review conditions were satisfactory. 3498

Phosphate

Phosphate mining involves the removal of hard phosphate nodules from an otherwise (mostly) sedimentary environment. This means that suitable hard habitat, needed by sessile organisms such as corals, is removed. In addition, as a number of these organisms create habitat themselves (biogenic habitat), it has direct repercussions for associated species potentially resulting in a significant shift in community structure.

Once the phosphate nodules have been removed, the finer non-phosphatic sediments and seawater used to produce the slurry for the phosophorite nodule extraction and will be discharged on or near the seafloor, resulting in a sediment plume. The range of potential impacts from phosphate mining is described in more detail in the case study below.

Seafloor massive sulphides

Active deep-sea vents, where SMS are found, are associated with highly unusual and productive communities that rely on sulphur compounds as an energy source. These communities were only discovered in 1977 3499  and remain poorly understood. The environments around active vents, and the communities they support, are dynamic and subject to irregular flows of hot fluid.

Mining of SMS will leave permanently altered areas at the mine site, with surrounding areas potentially impacted by the sediment plume. The spatial scale of the impacted zone is dependent on the volumes of mined material, and the bottom current regime. 3500  In areas of active hydrothermal venting, species may be adapted to natural changes in the environment, and therefore be able to re-colonise more rapidly than other deep-sea communities, dependent upon there being a viable source of recruits nearby. 3501

Example of SMS mining system and related sources of potential environmental impacts (Source: Secretariat of the Pacific Community, 2013A)

A major minerals research programme in New Zealand, led by GNS Science, aims to gain a better understanding about how these minerals are formed. The programme is also considering the development of effective exploration and extraction practices. This research is currently examining SMS mineralisation along the Kermadec Arc and in Frontier regions, including the Colville Ridge and Kermadec Ridge. 3502  The work should assist with building a deeper understanding of how these minerals form and the environments surrounding them.

Manganese nodule mining

The excavation of manganese nodules would disturb parts of the seabed. Potentially large amounts of sediment, water and many organisms would be dug up with the nodules (depending on the method proposed), and the destruction of the deep-sea habitat could be substantial. 3503  Nodules take millions of years to form, so that these habitats would be permanently lost from large areas of seabed following mining. 3504

The environmental impacts from exploration and mining for manganese nodules are highlighted in the figure below and summarised as: 3505

  • Destruction of the benthic community in mining area including organisms living in the crevices of the nodules which would be permanently lost.
  • Removal of the nodules leaves behind a sediment plain suitable only for a subset of the original benthic community. Nodules will not reform for millions of years.
  • Mobilisation of sediment into the water column, which is potentially a major concern for the affected ecosystem, as currents at that depth are often very slow, as is the settling velocity of the disturbed material.
Example of seafloor manganese nodule mining system and related sources of potential environmental impacts (Source: Secretariat of the Pacific Community, 2013B)

Cobalt crust mining

Seamounts studied to date, show that there is an abundance of life associated with some of them, including corals and sponges and huge aggregations of fish. Seamounts have been described as “underwater oases”, and they can be important habitats for migrating species. Mining in the vicinity of these structures will destroy any corals and sponges which grow on the seamounts. This removal of habitat-forming species is significant, and recent studies indicate that recovery times would be decades to centuries. 3506

The environmental impacts from exploration and mining for cobalt crusts are highlighted in the figure below and summarised as: 3507

  • Removal of material from the summit of seamounts, and scraping the crusts of underlying rocks will kill sessile marine life
  • Plumes from the mobilised sediment will impact life in surrounding area
  • Rock surfaces left behind will be re-colonised over timeframes that are largely unknown (but likely to be slow)
Example of seafloor ferromanganese crust mining system and related sources of potential environmental impacts (Source: Secretariat of the Pacific Community, 2013C)

Methane hydrate

The methane gas is trapped at such pressure that when released at the surface it expands 160 times, presenting both a massive technological challenge for extraction and a hazard. 3508  There is the potential for collapsing of areas of the seabed following the extraction of the methane. Such areas of collapse would devastate any marine life in the mining area.

There is still much work to be done on the potential environmental impact from methane hydrate extraction activities. Scientists from GNS Science, NIWA, and the universities of Otago and Auckland have begun a government-funded project for the Hikurangi Margin. NIWA will provide detailed information on the stratigraphic and geological architecture of the reservoirs and surroundings, and establish an ecological and biological baseline of potential exploration sites. These studies will be critical for management and environmental protection of any mining sites. The aim is to assess optimal sites by 2015, with test drilling scheduled by 2018. 3509

  1. Extracted from Secretariat of the Pacific Community, 2013

  2. Adapted from Secretariat of the Pacific Community, 2013, various Environment Court cases and EEZ marine consent processes

  3. Thompson K, 2012, Maui’s and mining: A review of marine mineral mining activity on the West Coast of New Zealand and its potential impacts, page 27, Prepared for Department of Conservation Auckland Area Office, Department of Conservation, Auckland

  4. Thompson K, 2012, Maui’s and mining: A review of marine mineral mining activity on the West Coast of New Zealand and its potential impacts, page 27, Prepared for Department of Conservation Auckland Area Office, Department of Conservation, Auckland

  5. Haggitt T, S Mead and M Bellingham, 2008, Review of environmental information on the Kaipara Harbour marine environment, Prepared by ASR/CASL for Auckland Regional Council, Auckland Regional Council Technical Publication No.354, Auckland

  6.  NIWA, 2012, Expert risk assessment of activities in the New Zealand exclusive economic zone and extended continental shelf , Prepared for the Ministry for the Environment, National Institute of Water & Atmospheric Research Ltd, Wellington

  7. NIWA, 2012, Expert risk assessment of activities in the New Zealand exclusive economic zone and extended continental shelf , Prepared for the Ministry for the Environment, National Institute of Water & Atmospheric Research Ltd, Wellington

  8. De Lange, W, 2014, pers. comm., 6 August 2014

  9. Oruawharo Marae Trust v Auckland Regional Council NZEnvC A113/2006

  10. Oruawharo Marae Trust v Auckland Regional Council NZEnvC A113/2006

  11. NIWA, 2012, Expert risk assessment of activities in the New Zealand exclusive economic zone and extended continental shelf , Prepared for the Ministry for the Environment, National Institute of Water & Atmospheric Research Ltd, Wellington

  12. Thompson K, 2012, Maui’s and mining: A review of marine mineral mining activity on the West Coast of New Zealand and its potential impacts, Table 5, Prepared for Department of Conservation Auckland Area Office, Department of Conservation, Auckland

  13. De Lange, W, 2014, pers. comm., 6 August 2014

  14. De Lange, W, 2014, pers. comm., 6 August 2014

  15. Haggitt T, S Mead and M Bellingham, 2008, Review of environmental information on the Kaipara Harbour marine environment, Prepared by ASR/CASL for Auckland Regional Council, Auckland Regional Council Technical Publication No.354, Auckland

  16. The Friends of Pakiri Beach v The Auckland Regional Council and Anor HC AK CIV-2006-404-3544 [26 March 2009]

  17. Haggitt T, S Mead and M Bellingham, 2008

  18. http://www.nrc.govt.nz/upload/3465/Natural%20Character%20of%20the%20Coast.pdf

  19. Sea-Tow Limited v Auckland Regional Council A066/06

  20. Peart R and K Mulchay, 2010, Appendix One

  21. NIWA, 2012, Expert risk assessment of activities in the New Zealand exclusive economic zone and extended continental shelf , Prepared for the Ministry for the Environment, National Institute of Water & Atmospheric Research Ltd, Wellington

  22. Suhr, 2008, 113

  23. NIWA, 2012, Expert risk assessment of activities in the New Zealand exclusive economic zone and extended continental shelf , Prepared for the Ministry for the Environment, National Institute of Water & Atmospheric Research Ltd, Wellington

     

  24. Oruawharo Marae Trust v Auckland Regional Council A083/06

  25. Secretariat of the Pacific Community, 2013A

  26. Secretariat of the Pacific Community, 2013E

  27. Secretariat of the Pacific Community, 2013E

  28. http://www.gns.cri.nz/index.php/Home/Our-Science/Earth-Science/Ocean-Floor-Exploration/Oceans-Research/Geological-Exploration-of-the-EEZ

  29. Bollmann M, T Bosch, F Colijn, R Ebinghaus, R Froese, K Güssow, S Khalilian, S Krastel, A Körtzinger, M Langenbuch, M Latif, B Matthiessen, F Melzner, A Oschlies, S Petersen, A Proelß, M Quaas, J Reichenbach, T Requate, T Reusch, P Rosenstiel, J O Schmidt, K Schrottke, H Sichelschmidt, U Siebert, R Soltwedel, U Sommer, K Stattegger, H Sterr, R Sturm, T Treude, A Vafeidis, C van Bernem, J van Beusekom, R Voss, M Visbeck, M Wahl, K Wallmann and F Weinberger, 2010, World ocean review: Living with the oceans, Maribus, Hamburg. 

  30. Allsopp M, C Miller, R Atkins, S Rocliffe, I Tabor, D Santillo and P Johnston, 2013, Review of the current state of development and the potential for environmental impact of seabed mining operations, University of Exeter, Exeter, available at http://www.greenpeace.to/greenpeace/wp-content/uploads/2013/07/seabed-mining-tech-review-2013.pdf

  31. Secretariat of the Pacific Community, 2013E

  32. Allsopp M, C Miller, R Atkins, S Rocliffe, I Tabor, D Santillo and P Johnston, 2013, Review of the current state of development and the potential for environmental impact of seabed mining operations, University of Exeter, Exeter, available at http://www.greenpeace.to/greenpeace/wp-content/uploads/2013/07/seabed-mining-tech-review-2013.pdf

  33. Secretariat of the Pacific Community, 2013E

  34. http://www.niwa.co.nz/publications/wa/water-atmosphere-2-february-2011/oceans-treasure

  35. http://www.niwa.co.nz/publications/wa/water-atmosphere-2-february-2011/oceans-treasure

  36. Thompson K, 2012, Maui’s and mining: A review of marine mineral mining activity on the West Coast of New Zealand and its potential impacts, page 27, Prepared for Department of Conservation Auckland Area Office, Department of Conservation, Auckland

  37. NIWA, 2012, Expert risk assessment of activities in the New Zealand exclusive economic zone and extended continental shelf , Prepared for the Ministry for the Environment, National Institute of Water & Atmospheric Research Ltd, Wellington

Last updated at 11:26AM on January 10, 2018