Balancing ocean protection and use

In recent years, the role of the ocean in climate policy has moved up both inter­national and German political agendas. Al­though the ocean was long viewed primari­ly as a victim of acidification and warming, it is increasingly being seen as part of the solution to the climate crisis. The need to actively remove CO₂ from the atmosphere has become a central topic of debate, par­ticularly since achieving net-zero greenhouse gas emissions became a central objective of climate policy. Various carbon dioxide removal (CDR) approaches are currently being researched and developed worldwide, including in Germany.

The ocean plays a crucial role in regulating the global climate because it naturally absorbs approximately 25–30 per cent of anthropogenic CO₂ emissions. Human inter­vention may further increase this removal potential. As the technical and socio-politi­cal costs of land-based CDR approaches become increasingly apparent, the ocean may offer new opportunities, especially as long-term strategies for carbon removal and storage continue to evolve in Germany, the EU, and globally.

Proposals for enhancing the ocean’s role as a carbon sink range from expanding sea­grass meadows to geochemical approaches. The latter seek to increase ocean alkalinity through the addition of sub­stances such as ground limestone or olivine, which react with seawater and bind CO₂. At the same time, marine conservation remains a key political issue at the national, European, and international levels. There is a strong coalition of stakeholders pushing to priori­tise this issue.

Obligations under UNCLOS

One of the most important conclusions of the ITLOS advisory opinion is that anthropogenic greenhouse gas emissions released into the atmosphere constitute marine pollution as defined in UNCLOS (para. 179 of the advisory opinion). In reaching this conclusion, the Tribunal broke down the definition of marine pollution set out in Article 1 of UNCLOS into its three constituent parts and stated that: (1) there must be a substance or energy; (2) this substance or energy must be introduced by humans, directly or indirectly, into the marine environment; and (3) such introduction must result or be likely to result in delete­rious effects. It was further noted in the ITLOS opinion that, although the three criteria must be understood as cumulative, the definition of marine pollution in UNCLOS is otherwise “general in that it encompasses whatever satisfies these criteria” (para. 161).

This finding means that Article 194 of UNCLOS applies, which requires states to take all necessary measures to prevent, reduce, and control marine pollution, irrespec­tive of its source. The Tribunal emphasised that Article 194 grants each state discretion in determining which measures are neces­sary.

Certain passages of the opinion suggest that ITLOS views “marine geoengineering” approaches (an umbrella term that includes all types of mCDR) not primarily as in­stru­ments for combating climate-related pollu­tion but as activities that may them­selves generate pollution. The Tribunal noted: “Article 195 of the Convention requires States, in taking measures to prevent, re­duce and control pollution of the marine environment, not to transfer, directly or indirectly, damage or hazards from one area to another or transform one type of pollution into another” (para. 231). The advisory opinion goes on to state: “Marine geoengineering would be contrary to article 195 if it has the consequence of transforming one type of pollution into another” (para. 231).

Activities such as ocean fertilisation would likely meet the three criteria for marine pollution established by ITLOS: (1) there is a substance (e.g. iron); (2) it is introduced into the marine environment through human activities; and (3) it could have harmful effects, such as algal blooms or nutrient depletion. The same may apply to various other mCDR approaches, such as increasing the alkalinity of the ocean. Con­sequently, states that deploy or authorise such technologies could potentially be in violation of UNCLOS.

At the same time, other parts of the ad­visory opinion may be interpreted as recog­nising mCDR as a means of protecting and preserving the marine environment. Article 192 of UNCLOS obliges states to protect and preserve the marine environment. Accord­ing to ITLOS, this obligation is broad and encompasses all forms of harm or threats to the marine environment, including those arising from climate change (paras. 385 and 388). In this regard, the statement reads: “Where the marine environment has been degraded, the Tribunal is of the view that the term ‘preservation’ may include restor­ing marine habitats and ecosystems” (para. 386). Because some mCDR approaches could support those aims – for example by restoring seagrass ecosystems or mitigating ocean acidification – they may be con­sidered permissible. The advisory opinion therefore remains ambiguous. It can be used to interpret certain marine CDR activi­ties both as a source of marine pollution and as a means of protecting the seas.

Implications for climate and ocean governance

This ambiguity is likely to influence numer­ous ongoing climate and ocean policy pro­cesses in Germany, the EU, and inter­nationally. Following the entry into force of the BBNJ Agreement in January 2026, future regulation of mCDR will likely be subject to stricter environmental requirements. The BBNJ stipulates that activities which may cause significant pollution or harmful environmental changes on the high seas can only be authorised following comprehensive environmental impact assessments. Interpretations of the ITLOS opinion that classify mCDR as pollution could be used to justify such assessments for all mCDR projects. Conversely, interpretations emphasising restoration and con­servation functions could be invoked to argue against stringent assessment require­ments.

The opinion may also shape inter­national debates regarding the incorporation of ocean carbon cycles into Nationally Determined Contributions (NDCs), national emissions inventories, and blue-carbon credit trading under the Paris Agreement. By confirming states’ obligations to reduce marine pollution caused by greenhouse gases while leaving open whether certain mCDR approaches contribute to that ob­jective, the opinion may strengthen argu­ments for including ocean-based carbon removal within climate governance frame­works. At the same time, it may encourage demands for more rigorous standards con­cerning monitoring, reporting, and verifi­cation, as well as stronger biodiversity safe­guards.

At the EU level, the Carbon Removal Certification Framework was adopted in 2024, and methodologies for certifying both land-based and marine CDR are currently under development. If mCDR technologies are to be integrated into EU climate policy, policymakers will need to address the legal and regulatory questions raised by the ITLOS opinion.

At the national level, Germany has emphasised the importance of CDR in its overall climate strategy and has initiated discussions on a long-term carbon removal strategy to counterbalance its residual emis­sions. Amendments to legislation governing marine field trials have recently expanded opportunities for testing mCDR technologies in German waters. Future permitting procedures will need to deter­mine whether specific mCDR activities should be classified as pollution or as measures supporting climate and marine protection.

Strategically navigating ambiguity

Germany and the EU should prepare for different actors to invoke the ITLOS ad­visory opinion in support of different ob­jectives. Some states and interest groups are likely to use the opinion to justify pre­cautionary regulation and stricter environmental requirements for mCDR. Others may interpret it as support for accelerating technological development and integrating mCDR into climate policy. These debates are already visible in discussions about the planned Intergovernmental Panel on Climate Change (IPCC) methodology report on CDR approaches. These debates show that different coalitions are already forming around the question of how mCDR should be assessed and regulated.

During the negotiations, Belgium, Germany, France, Austria, Palau, and Switzerland opposed the inclusion of a separate chapter on marine CDR processes in the report. They pointed to unresolved issues regarding effectiveness, scalability, environ­mental impacts, and legal admissibility. In contrast, some other countries – led by Saudi Arabia – called for all CDR technologies recognised by experts, including marine approaches, to be given equal con­sideration. mCDR is increasingly becoming a contested field of political and regulatory negotiation in which coalitions of states mobilise competing interpretations of scien­tific evidence and international legal obligations. Germany and the EU should therefore clarify at an early stage which interpretation they intend to support with­in future international climate and ocean governance processes.