Editorial: Ocean negative carbon emissions technologies and ecological risks

## Our Take: Navigating the Promise and Peril of Ocean Carbon Dioxide Removal

The recent surge in interest and investment surrounding ocean-based carbon dioxide removal (CDR) technologies is both encouraging and demands careful scrutiny, as highlighted in this week’s editorial concerning ecological risks. The concept – utilizing the ocean’s vast capacity to absorb and store carbon – holds undeniable appeal in the face of escalating climate change. Proposals range from ocean alkalinization and electrochemical methods to enhanced weathering and macroalgae cultivation. However, the editorial rightly cautions against a rush to deployment without thoroughly understanding the potential unintended consequences. The ocean is a complex, interconnected system, and interventions at this scale risk disrupting delicate balances with potentially cascading effects. For those seeking deeper understanding of the challenges in modelling these systems, Ocean Carbon Dioxide Removal: A Scientific Assessment provides a robust overview of current research and limitations. The editorial’s emphasis on rigorous, longitudinal studies is essential; we cannot afford to trade one environmental crisis for another. The sheer scale of carbon removal needed to meet global climate goals means these technologies are being considered with increasing urgency, but that urgency should not eclipse the need for meticulous assessment.

The challenge isn’t simply about proving the technical feasibility of CDR methods, but about anticipating and mitigating the ecological impacts. Ocean alkalinization, for instance, aims to increase the ocean's alkalinity, enhancing its ability to absorb CO2. However, altering ocean chemistry can affect marine organisms, particularly those reliant on calcium carbonate for shell formation. Similarly, large-scale macroalgae cultivation, while potentially beneficial for carbon sequestration, could disrupt local ecosystems and compete with existing fisheries. The editorial’s call for a precautionary approach, prioritizing ecosystem-based monitoring and adaptive management, is paramount. We need integrated data ecosystems that can rapidly assess the impacts of these interventions, allowing for course correction before irreversible damage occurs. The World Data Ocean’s mission is fundamentally about building that capacity; providing the validated, measurable data required for informed decision-making. This includes improved calibration of climate indicators and real-time monitoring of ocean conditions – resources which are, frankly, chronically underfunded despite their critical importance. For a detailed look at the state of ocean observation and data gaps, see Global Ocean Observing System (GOOS) Status Report.

Beyond the immediate ecological risks, the editorial also implicitly raises questions about governance and equity. Who decides where these technologies are deployed? How are potential impacts distributed across different regions and communities? The ocean is a shared resource, and any interventions must be undertaken with transparency and international collaboration. Furthermore, the focus on CDR should not detract from the primary imperative of reducing greenhouse gas emissions at the source. CDR should be viewed as a complementary strategy, not a substitute for ambitious mitigation efforts. The promise of a technological fix should not lull us into complacency regarding the fundamental need to transition to a low-carbon economy. We need to ensure that investments in CDR do not divert resources from proven mitigation strategies, nor exacerbate existing inequalities. The development of validated methodologies for assessing the lifecycle carbon accounting of these technologies, including embedded energy and material inputs, is critical for ensuring they deliver net-negative emissions.

Looking ahead, the crucial question is whether we can develop a framework for responsible ocean CDR that balances the urgent need for climate action with the imperative of ecological stewardship. The integration of artificial intelligence and machine learning into ocean monitoring and modeling offers unprecedented opportunities for predicting and mitigating potential impacts. However, these tools are only as good as the data they are fed, highlighting the ongoing need for robust, peer-reviewed ocean data collection and analysis. Can we develop the global governance structures and the scientific capabilities necessary to navigate this complex landscape, ensuring that ocean-based CDR contributes to a sustainable future, rather than creating new and unforeseen challenges? The answer will depend on a commitment to transparency, collaboration, and a willingness to adapt our strategies as new evidence emerges.