Janos Pasztor*
“The risks of inaction now clearly outweigh the risks of innovation—with responsibility.”
A cautionary tale from the past
In 2012, a large-scale ocean fertilization experiment was carried out off the coast of British Columbia, spreading iron oxide and sulfate into the Pacific Ocean to stimulate a phytoplankton bloom. The goal was to enhance salmon populations and sequester atmospheric carbon. However, some organizations thought that the project was carried out without sufficient international consent and transparency, and bypassed environmental safeguards.
The experiment triggered concerns as it was not conducted in a confined manner. In response, the Convention on Biological Diversity (CBD) reaffirmed its earlier moratorium on ocean fertilization (initially adopted in 2008), stating that such activities should be restricted to small-scale scientific research, conducted under stringent conditions and in line with international law.
Simultaneously, under the London Convention and its Protocol (LC/LP), key international parties governing ocean pollution adopted a resolution in 2008 on ocean fertilization, and then a broader resolution in 2013 to regulate marine geoengineering activities. This included a framework for risk assessments and permitting, laying the groundwork for international oversight of ocean fertilization. Though it did not become legally binding for all countries, it set a critical precedent.
These responses served as early governance milestones, designed primarily to prevent environmental harm from speculative and unvetted activities. But today, the context has changed dramatically—and with it, the conversation must evolve.
Why we need “everything”: the climate emergency escalates
Despite progress in clean energy technologies (solar photovoltaics are now among the cheapest sources of electricity) and electric vehicle adoption, global emissions are still increasing. The UNEP Emissions Gap Report 2024 warns that the world remains far off the trajectory needed to limit global warming to 1.5°C. Even under full implementation of current Nationally Determined Contributions (NDCs), the planet is on track for 2.6–3.1°C of warming this century. Currently average warming over the last 20 years is 1.3°C, and its impacts are already significant and often catastrophic. Avoiding the doubling of such warming therefore is key.
Meanwhile, geopolitical and geoeconomic instability and policy rollbacks in key regions have cast further doubt on the world’s ability to meet its climate commitments. These developments complicate the global response to climate change.
Against this sobering backdrop, the Intergovernmental Panel on Climate Change (IPCC) has made one thing clear: we must reduce emissions and remove carbon from the atmosphere at a large scale. Every pathway to net zero that limits warming to 1.5°C or 2°C includes some form of carbon dioxide removal (CDR)—whether nature-based (like reforestation) or technological (like direct air capture).
And here, the ocean, our planet’s largest carbon sink, has a role to play.
Marine CDR: Exploring the potential of the ocean
The ocean already absorbs roughly 25% of human-caused CO₂ emissions each year. Scientists are now investigating ways to enhance this natural carbon sink through marine CDR approaches. Among these, ocean fertilization, adding iron to stimulate phytoplankton growth, has attracted renewed attention.
Phytoplankton draw down carbon dioxide during photosynthesis, and when they die, some sink to the deep ocean, potentially storing carbon for decades, centuries and even longer. Recent modeling suggests that if done responsibly and at scale, ocean fertilization could remove 1–3 gigatonnes of CO₂ annually(1).
Other marine CDR options include artificial upwelling, alkalinity enhancement, and seaweed cultivation (the latter assuming that the harvested seaweed is sunk), all of which are being explored for their sequestration potential and environmental impacts.
While none of these methods is a silver bullet, the scale of the climate crisis requires a diversified portfolio of mitigation and removal strategies. The case for “everything”, as long as it’s done responsibly, is growing stronger by the day.
Beyond carbon: oceanry’s holistic approach to marine CDR
Recognizing the multifaceted challenges facing our oceans, organizations like Oceanry advocate for marine CDR strategies that deliver co-benefits beyond carbon removal. Oceanry emphasizes the development and deployment of techniques that not only sequester atmospheric CO₂ but also:
- Restore marine biodiversity: By enhancing habitats and supporting the recovery of marine species.
- Reduce ocean acidification: ocean acidification can be reduced locally and temporarily, helping to stabilize pH levels and protect calcifying organisms.
- Enhance ocean albedo: Phytoplankton blooms release aerosols which support in the formation of more and brighter low-level clouds. This reflects more incoming solar radiation back into space—a phenomenon known as the Twomey effect.
This integrated approach aims to address multiple environmental issues simultaneously, ensuring that marine CDR efforts contribute to the overall health and resilience of ocean ecosystems.
Remembering responsibility, risk, and the governance gaps
Still, ocean iron fertilization remains scientifically unvalidated on a large scale. If done in too hot waters or too close to the shore, there are risks such as harmful algae blooms or oxygen depletion. With a balanced research approach including a controlled environment, permanence and monitoring, the potential disruption of marine ecosystems can be better understood and mitigated.
Existing governance frameworks, the CBD and LC/LP, provided important early restrictions. But these were primarily reactive, developed to prevent unregulated activities rather than to support responsible innovation and necessary change.
The Carnegie Climate Governance Initiative (C2G) emphasized in various reports on governance, including on marine CDR. What’s needed now is a more enabling and anticipatory model of governance—one that supports legitimate scientific research while ensuring transparency, accountability, and environmental safeguards.
This includes:
- Clear criteria for evaluating research proposals;
- Rigorous environmental and social impact assessments;
- Mechanisms for international coordination and public consultation;
- Special attention to equity, including participation from developing nations and Indigenous communities.
Without such governance innovation, the world risks repeating the mistakes of the past—or missing a critical opportunity to build new solutions.
More recently, at a meeting of the LC/LP governing bodies in 2024, some countries (e.g., the UK and the USA) made helpful statements in the direction of also considering the benefits of leveraging the marine environment to boost the carbon sequestration, especially in the context of net zero objectives under the Paris Agreement.
A call to action: build governance to unlock safe solutions
The debate is no longer about whether ocean iron fertilization should be allowed or banned outright. It is about how to enable responsible research and development to better understand the risks, benefits and governance challenges, and then to govern a portfolio of climate responses with integrity, equity, and urgency.
We already have building blocks: the CBD’s emphasis on precaution; the London Protocol’s early permitting framework; the UN’s GESAMP Working Group 41’s draft ‘Ocean Interventions Assessment Framework’; and new proposals from actors like Oceanry. Now, we must build on them to:
- Update international frameworks to reflect climate urgency and enable responsible R&D;
- Support scientific collaboration with open data sharing and inclusive participation;
- Align marine CDR with ocean conservation goals, such as the UN Decade of Ocean Science and 30×30 marine protection targets;
- Ensure that governance of CDR methods is linked comprehensively to other climate governance (e.g., for emission reductions, adaptation and potential albedo modifications) to reduce moral hazard issues, and to broader sustainable development efforts (e.g., the Sustainable Development Goals);
- Design governance that can evolve with the science, technology, and geopolitics of the coming decades.
The risks of ocean fertilization are real, but so are the risks of inaction. The climate clock is ticking, and the ocean is a too important carbon sink to be left behind.
With better science, stronger governance, and shared purpose, ocean iron fertilization can be responsibly explored as part of a just and effective response to climate change.
The time to govern is now – proactively, not reactively.
Janos Pasztor
Former Executive Director of the Carnegie Climate Governance Initiative – C2G
Former UN Assistant Secretary-General for Climate Change
Geneva, 29 April 2025
Footnote:
¹ Estimates based on climate modeling suggest that large-scale and responsibly implemented ocean iron fertilization (OIF) could remove between 1–3 gigatonnes of CO₂ per year.
See:
- The Royal Society (2009). Geoengineering the climate: Science, governance and uncertainty. https://royalsociety.org
- IPCC AR6 Working Group III (2022). Climate Change 2022: Mitigation of Climate Change. Chapter 12, CDR methods.
- Fuhrman, J. et al. (2023). The role of ocean-based carbon dioxide removal in climate policy. Nature Climate Change, 13, 25–31. https://doi.org/10.1038/s41558-022-01533-8
