Environmental Impact Assessment in deep sea mining. Environmental Impact Assessment (EIA) is an integral component of planning, development, and management of various industrial activities. It is widely implemented in many national jurisdictions and industrial developments. However, the application of EIA and related environmental management frameworks remains underdeveloped for deep-sea mining.

Conducting EIAs for deep-sea mining is challenging due to the fragile and unique nature of deep-sea ecosystems, insufficient scientific knowledge, and technological limitations. The deep sea remains poorly understood, with limited baseline data on its biodiversity and environmental conditions. Many species are slow-growing and highly sensitive to disturbance, and the long-term impacts of mining activities, such as habitat destruction, sediment plumes, and noise pollution, remain difficult to predict. The extreme conditions of the deep sea, including high pressure and low temperatures, make data collection and monitoring costly and technically demanding. Governance issues also arise, as the formulation of EIA standards for seabed mining beyond national jurisdictions requires complex international coordination between actors with contradicting interests. Furthermore, the potential for irreversible and cumulative impacts on marine ecosystems underscores the need for stronger monitoring, scientific research, and precautionary measures compared to terrestrial projects.

Legal framework 
The United Nations Convention on the Law of the Sea (UNCLOS) outlines general duties for states to safeguard the marine environment (Articles 145, 192) and specifies in Article 206 that planned activities with the potential to cause significant harm must undergo an assessment of their potential effects, with findings duly reported. UNCLOS does not specify detailed requirements for conducting such assessments, leaving the exact interpretation ambiguous.

The International Seabed Authority (ISA) plays a central role in developing the legal framework for EIAs in deep-sea mining, viewing EIA as essential for minimizing environmental impacts. The ISA aims to fulfill obligations such as implementing a precautionary approach and ensuring effective protection of the marine environment, as required under UNCLOS Part XI, Article 145 . Although processes and forms remain incomplete, the EIA regulations of ISA define governing bodies, licensing frameworks, and permitting processes.

Examples of EIA for deep sea mining 
Deep-sea mining remains in the exploratory phase, with no fully developed commercial projects; however, several contractors operating under the ISA framework have conducted EIAs for exploratory and pilot-scale mining activities:
 In 2018, the German Federal Institute for Geoscience and Natural Resources and Global Sea Mineral Resources submitted an Environmental Impact Statement for testing a nodule collector vehicle in the Clarion-Clipperton Zone.
 In 2020, the Government of India submitted an Environmental Impact Statement for technical trials in the Indian Ocean.
 In 2021, Nauru Ocean Resources Inc. submitted an Environmental Impact Statement for technical trials in the Clarion-Clipperton Zone.

ISA process for EIA 
Since its establishment, the International Seabed Authority (ISA) has implemented measures to assess the environmental impacts of deep-sea mining activities at various stages, in line with its obligations under Article 145 of UNCLOS. ISA has provided guidelines to contractors for conducting environmental impact assessments related to mineral exploration in the Area. These guidelines outline general procedures for collecting baseline data and conducting monitoring during and after exploration activities.

Prospecting phase 
During the prospecting potential mining areas, no prior contact to the ISA is necessary in theory. However, all three mineral deposits in the area are covered under the ISA Exploration Regulation which obligates relevant parties to notify the ISA of its intention to initiate prospecting activities. For the next phase of exploration applicants are required to submit a 5-year work plan as well as a preliminary assessment of possible environmental impacts. The submission is confidentially assessed by the Legal and Technical Commission (LTC) of the ISA. The LTC then provide recommendations consisting of a list of activities that may be conducted during the exploration phase.

Exploration phase 
During the exploration phase, contractors, sponsoring States, and other relevant parties are mandated to collaborate with the ISA in establishing and executing monitoring and evaluation programs to address the environmental impacts of deep-sea mining. In accordance with the LTC Recommendations, exploration contractors planning activities classified by the ISA as potentially causing significant harm to the marine environment must submit Environmental Plans. This includes an Environmental Impact Statement (EIS) at least 12 months before commencing such activities, a Closure Plan, and a Monitoring Plan. Following a consultation and review process from LTC, the Secretary General, members of the ISA, and other stakeholders, the LTC will proceed with evaluating the application for the approval of a plan of work and submit its recommendation to the Council on whether to approve or reject the application.

Exploitation phase 
Under the current draft exploitation regulations, contractors awarded an exploitation contract must submit a feasibility study at least 12 months before commencing commercial production. Based on the feasibility study, contractors may need to amend their approved plan of work if a "material change" occurs. Additionally, contractors can independently request modifications to their plan of work, with any "material change" requiring a formal approval process by the ISA.

Challenges to developing EIAs

Uncertainty and data shortcomings 
Conducting comprehensive EIAs for deep-sea mining is particularly challenging due to the limited availability of data. The remote location and challenging conditions of the deep sea—such as high pressure and low temperatures—make exploration costly and reliant on advanced technologies. Within both national borders and in international waters the deep sea is poorly studied, and specific locations are entirely unexplored. Especially the understanding of deep-sea ecosystems, their connections to other parts of the ocean, and their function within Earth's systems. Limited data leaves the potential impacts of mining and strategies for mitigating them largely speculative.

Criticism of EIA procedures 
The ISA's EIA procedures have been criticized for lacking comprehensiveness and procedural rigor:
 Management of uncertainty: The decision-making process has been criticized for lacking procedural and institutional measures to address uncertainty. Applicants for exploration contracts are not required to identify or address uncertainties in their project plans.
 Influence on decision-making: Mechanisms to ensure EIAs influence decision-making have been criticized for being inadequate, illustrated e.g. through how applicants can secure a 15-year exploration contract before completing an EIA, and amendments to the contract requires the consent of both parties.
 Institutional capacity: The ISA has been criticized for lacking the capacity to manage extensive environmental responsibilities. High personnel demand for EIA processes, an overstretched LTC, and limited Council meetings hinder decision-making in a growing deep sea mining regime.
 Frameworks: The EIA guidelines of ISA have been criticized for being overly generic and failing to address the specific challenges unique to deep-sea mining.

References 

 Environmental impact assessment