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Defining the environmental impact assessment process for deep-sea mining

Holly Niner and Kirsty McQuaid

One Ocean Hub, University of Strathclyde, UK

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  • environmental impact assessment,
  • deep sea
Target Group
  • Researchers
  • English

The International Seabed Authority recently held a consultation on a series of draft ‘Standards and Guidelines’ which set out how impact assessment of deep-sea mining projects should be undertaken.

The documents are a component of the Mining Code intended to operationalise the exploitation regulations and outline the process and criteria by which projects will be appraised for acceptability and granted permission. Members of the One Ocean Hub from the University of Plymouth reviewed and responded to this consultation. Several key areas of concern were raised relating to the weak definition of ‘best practice’ and poorly defined compliance processes.


Deep seabed mining involves the extraction of minerals, those commonly targeted include polymetallic nodules (nodules), cobalt crusts (crusts), and seafloor massive sulfides (SMS) associated with hydrothermal vents. Interest in extraction is growing driven by expansion of global blue economies and through perceived demands for materials to fuel the renewables transition.

The extraction of these minerals equates to removal of habitat and organisms many of which are sensitive to anthropogenic disturbance and slow to recover. Indirect impacts arising from deep-sea mining include the smothering of habitat and biota outside of the mine-site by sediment plumes, the spread of nutrients or toxins via plumes and other forms of disturbance (e.g. light, noise). Accordingly, deep-sea mining inevitably leads to biodiversity loss, with recovery unlikely on meaningful human timescales. However, the significance of this loss remains unknown given the untested technology and the lack of understanding of deep-sea ecosystem functioning. For example, we do not yet understand the role that deep-sea biodiversity plays in delivering vital ecosystem services, and how this links to fundamental issues of health and human rights.

The UN Convention on the Law of the Sea (UNCLOS) establishes the mandate of the International Seabed Authority (ISA) to “organise and control activities in the Area, particularly with a view to administering the resources of the Area.” ‘The Area’ refers to the seabed beyond the 200 nm limits of national jurisdiction. UNCLOS requires that the ISA manage mineral-related activities of the Area for the benefit of humankind as a whole – where both the Area and its resources are considered “the common heritage of mankind”. Central to the mission of the ISA is the “effective protection of the marine environment” and management that allows development of the Area’s resources to contribute “to agreed international objectives and principles, including the Sustainable Development Goals (SDGs).” Whilst the ISA does not govern seabed mining within nations’ exclusive economic zones (EEZs) within 200nm limits, deep-water mineral extraction is also being pursued in these areas. Management here is likely to reflect the progression of that developed and implemented by the ISA – the evolution of this is being carefully watched.

The ISA is currently developing regulations for commercial-scale deep-seabed mining – ‘The Mining Code’. This relates to both exploration and exploitation of minerals. If these regulations are to meet the mandate of the ISA to protect the marine environment, scientific and growing societal consensus is that progression of the deep-sea mining industry should be precautionary while understanding of its consequences is developed. Despite concerns that the industry is unable to meet the demands for conservation and sustainability set by UNCLOS, mining concessions have been granted to Contractors (both private companies and government bodies) and there are recent indications that deep-sea mining is set to take off in the near future.


Our submission to the ISA addressed the following issues: best practice, including expert judgment, minimum standards and socio-economic assessments; and issues of process, including thresholds, stakeholder consultation, and data sharing.


In their current draft form the Standards and Guidelines heavily reference best practice as the model that impact assessment should follow. Despite this reliance on best practice, the documents fall short of stating exactly what constitutes best practice and who decides what best practice looks like. The documents also indicate that best practice can be distilled from existing industrial practice including other offshore industries such as oil and gas.  However, Environmental Impact Assessment (EIA) and associated environmental consenting processes for marine industry have been critiqued for a tendency to focus on compliance or audit as opposed to meeting stated (and mandated) aims of environmental protection. While there are undoubtedly lessons to be learned from existing EIA practice, it is important to recognise that under current forms of ‘best practice’ marine ecosystem health has continued to decline. A blind reliance on precedent and existing practice risk continuing and exacerbating these trends of decline.

There are numerous areas outlined within the Standards and Guidelines where best practice is inferred as important but fails to outline what this constitutes. Further, there are other areas where best practice is equally important if the mandate of the ISA is to be met, but the documentation falls short of considering methodologies for their inclusion within impact assessment. We outline our key areas of concern over best practice in the following text.


The Standards and Guidelines outline a heavy reliance on expert judgement given anticipated high degrees of uncertainty in assessment. Again, detail is lacking in the documentation over how this should be undertaken and what might constitute best practice. It is not clear who and how ‘experts’ will be selected, the methods to be followed and how data should be included within impact assessment. To avoid bias and to ensure equitable, fair and robust decision-making a considered and methods-driven approach to the control and use of expert elicitation will be essential.


The draft Guidelines for the establishment of baseline environmental data outline what data should be collected and how. However, they do not outline a consistent approach for the prioritisation of data collection i.e. what is the essential information required for impact assessment. This unconstrained guidance leaves the selection of what is measured to the Contractor’s discretion, which could lead to huge inconsistency among Contractors with respect to methods and target receptors.

In our response to the consultation, we argue that a set of standards and/or obligatory minimum requirements should be established to support targeted question-driven and efficient data collection. This consistency is required to aid comparability of baseline data and to develop an understanding of the impacts of the nascent industry (on site and at scale). These could draw on existing standards and initiatives such as the Essential Ocean Variables and those being developed under the UN Ocean Decade including the Marine Life 2030DOOS, and Challenger 150.


The need for socioeconomic assessment of the potential impacts of deep-sea mining is stipulated in the exploitation regulations. However, the draft Standards and Guidelines do not contain any guidance for the collection, analysis and inclusion of social and economic baseline data, including that of ecosystem services and fall short of acknowledging the potential risks to cultural or spiritual connection to the deep sea.

While there are still large knowledge gaps relating to ecosystem services provided by the deep sea, it is generally considered to be important for essential processes supporting climate regulation, nutrient cycling and food provision among others and including cultural connection. We advise that the ISA needs to establish the standards for best scientific practice in the collection and analysis of this information to robustly assess impacts (both on site and at scale). In line with our advice with respect to baseline environmental data, these Standards will be essential to ensure consistency in data collection and impact assessment across Contractors and projects to understand the impacts of the industry.


In addition to concerns over the poor definition of best practice, we identified several areas where the process for EIA is weak. This leaves room for ambiguity, ad hoc interpretation and implementation of best practice, risking poor adherence to the mandate of the ISA for environmental protection.


Impact thresholds are a critical component of impact monitoring and assessment, by setting boundaries for acceptable limits of disturbance. In their current form, the draft Standard and Guidelines for impact assessment encourage Contractors to develop their own thresholds until such time as the ISA establishes them. While this is a pragmatic way forward to avoid consenting delays for Contractors, a lack of data to develop thresholds for the Area is clearly stated as a reason for the ISA not developing them. Such an ad hoc approach runs the risk of inconsistency in management and the establishment of a precedent of environmental damage.

Central to the majority of EIA processes and tests of impact acceptability is the mitigation hierarchy and this has also been adopted by the ISA within their Standards and Guidelines. The mitigation hierarchy stipulates that impacts follow the stepwise process of avoidance and minimisation whereby impacts are reduced as far as possible. After these steps are exhausted remediation is then considered, followed by the last resort of offsetting unavoidable losses through the creation of equivalent, additional biodiversity. By including the full mitigation hierarchy these documents put forward both restoration and biodiversity offsets as relevant to the seabed mining context. With residual biodiversity losses unavoidable given the extractive nature of deep-sea mining, and the challenge of restoration of deep-sea environments likely impossible on meaningful human timescales, offsets are considered inappropriate to manage the impacts of the industry. Accordingly, avoidance and minimisation of impacts are the only viable means of constraining biodiversity losses from deep-sea mining. As a result, caution in progression of the industry is recommended to allow for the integration of knowledge as it develops, such as through the careful monitoring of impacts to ensure that acceptable thresholds of environmental damage are not breached.


In our response we argue that tests of impact significance should be assessed at all relevant scales and against relevant international law, including the requirements of the Common Heritage of Humankind under the law of the sea and international human rights law. This is particularly relevant when considering the potential disruption to deep-sea ecosystem services that may in turn restrict abilities for nations and communities to meet aims of no hunger (SDG 2) and health and wellbeing (SDG 3). The interdependencies of a healthy ocean, human rights and blue economies are discussed here.


Stakeholder consultation is a central component of fair and robust EIA. For an industry such as deep-sea mining involving the extraction of benefits that have been allocated as the common heritage of humankind, and where assessment of significance relies heavily on expert opinion, it is particularly important to ensure that all knowledge and viewpoints are considered. The current iteration of the Standards and Guidelines does not outline best practice for appropriate and comprehensive stakeholder consultation across all phases of EIA.

Specifically, key questions remain around how those who have been historically missed or marginalized from consultation can be included or notified of opportunities for consultation. We suggest consultation is required and advertised appropriately (with appropriate timescales) to ensure that all those interested in the exploitation of the Area are provided an opportunity to meaningfully participate. We also highlight the importance of considering whether capacity building efforts are necessary to support participation in consultation exercises by all affected parties.

The One Ocean Hub has previously made a submission to the ISA on the importance of transparency and respect for international human rights standards in relation to stakeholder engagement, notably with regard to those human rights that may be potentially negatively impacted by environmental damage caused by deep-seabed mining.


The ISA is mandated through the UN Convention on the Law of the Sea to implement mechanisms to promote capacity building, training and technical assistance to developing States. This is reflected in their Strategic Plan for 2019-2023, as well as the High-Level Action Plan for the same period. As a key factor relating to capacity development, data sharing supports and encourages collaboration amongst researchers and maximises benefits arising from investment in data collection, by both Contractors and the scientific research community. The provision of data should be an Industry Standard, not a guideline as is the case with the current documents, given the mandate of the ISA in relation to capacity building and data sharing. A standard format for data sharing (i.e. best practice) provided by the ISA would reduce the burden on data centres to transform data for further use. Additionally, this would support assessment of cumulative impacts at a regional scale that may arise from multiple operations.


Transparent decision-making is essential for the governance of the common heritage of humankind to demonstrate that the mandate set by UNCLOS is being met. Within the documentation, responsibility for the definition of best practice and process is largely deferred to Contractors, who are also the same entities seeking to profit commercially from the industry. This presents a conflict of interest and with a reliance on assessment on a project-by-project basis, also highlights the need for scientific capacity within the ISA to critically appraise each contract. Standards and Guidelines are critical to this, to ensure that practice and process are scientifically robust and executed on a level playing field.

While there has been much work carried out by the ISA to develop the draft exploitation regulations and accompanying Standards and Guidelines for seabed mining, there are many outstanding issues that require further attention. The scientific community advise precaution in progression of the industry yet there is increasing pressure to complete the draft regulations at pace. Research carried out under the One Ocean Hub seeks to highlight the connections between people and the deep sea, through understanding ecosystem services, their distribution, governance, legal framing and links to human wellbeing. Combining this research with that also being conducted to develop an understanding of how the social sciences and arts can assist in the integration of a variety of knowledge systems will assist future discussions and the ISA’s development of the mining code to meet the demands set by UNCLOS for the management of the deep sea.