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Ocean-based carbon dioxide removal may not be effective

Recent research on carbon dioxide removal has raised significant concerns about the effectiveness of nature-based methods for removing carbon dioxide (CO2) from the ocean.

This study highlights that a limited understanding of basic ocean processes is hindering progress in marine carbon dioxide removal (CDR), and the ongoing commercialization of some approaches is seen as premature and misguided.

Carbon dioxide removal and climate

Carbon dioxide removal is vital in combating climate change. As carbon dioxide levels rise due to human activities, the planet’s temperature increases, leading to severe weather, rising sea levels, and disrupted ecosystems.

Removing carbon dioxide from the atmosphere can help stabilize global temperatures and reduce the impact of climate change. Effective carbon dioxide removal methods can complement emissions reductions, ensuring a comprehensive approach to mitigating climate risks.

This process is crucial for achieving international climate goals, protecting biodiversity, and sustaining human health and well-being. Investing in carbon dioxide removal technologies and strategies is essential for a sustainable and resilient future.

Nature-based carbon dioxide removal

In a new paper, scientists from several leading institutions, including the University of East Anglia (UEA) and the University of Tasmania’s Institute for Marine and Antarctic Studies, have reviewed the effectiveness of four nature-based carbon removal techniques that utilize marine biological processes.

The methods include shellfish cultivation, seaweed farming, coastal blue carbon (using the restoration of seagrass, saltmarsh, and mangrove forests), and increasing whale populations through “re-wilding.”

The experts concluded that while these activities offer significant non-climatic benefits, they cannot provide a meaningful contribution to carbon dioxide removal. According to the researchers, these methods risk being “dead ends” for effective climate mitigation.

Challenges with marine-based carbon dioxide removal

To limit global warming to less than 2°C, both emissions reductions and substantial carbon dioxide removal are necessary.

Achieving this goal requires developing and massively scaling up multiple techniques to remove billions of tons of CO2 annually within the next 30-50 years.

However, the researchers argue that many new methods, particularly ocean-based CDR, are being proposed without sufficient checks and balances.

Insufficient understanding and oversight

The experts warned that the ocean-based approaches reviewed are being promoted without a thorough understanding of the fundamental science.

“Here, we focus on four ocean-based CDR methods that, in our opinion, are being advocated, not only by scientists, but also in many cases by the private sector, without due diligence on the underpinning fundamental science,” wrote the study authors.

“Proponents of these methods have an incomplete or incorrect grasp not only of how the ocean carbon cycle functions, but also the massive up-scaling needed to provide significant climatic benefits,” said Dr. Phil Williamson.

“Such upscaling brings other ocean processes into play that could cancel out the effectiveness of the proposed CDR approach. In each case, misunderstanding and knowledge gaps affect the credibility of carbon offset schemes.”

Modest contributions to carbon dioxide removal

Professor Philip Boyd, lead author from the University of Tasmania, pointed out that the non-climatic benefits of these actions could greatly exceed their modest or non-existent contributions to ocean-based carbon dioxide removal.

“Those advocating these approaches have given insufficient attention to basic constraints relating to ecosystem functioning and the ocean carbon cycle, for example, ignoring the many processes returning CO2 to the atmosphere, as well as the challenges of implementation at a climatically significant scale, the (in)security of carbon storage, and the many difficulties in reliable quantification of climatic benefits,” said Professor Boyd.

Need for better communication and research

The authors emphasize the need for better communication of the basic criteria for carbon dioxide removal viability using marine processes.

Safety, durability, verifiability, and scalability should be used to prioritize relevant research and development funding by governments and provide checks and balances for policymakers.

The study raises concerns over the opportunity costs – resources directed at these approaches that could be better invested in reducing emissions and other CDR methods, both land and ocean-based, that are more likely to be safe, sustainable, durable, verifiable, and scalable.

“We believe that the use of these four nature-based approaches for carbon offsets is more likely to represent greenwashing rather than these methods becoming the ‘climate heroes’ that some people are claiming,” concluded Dr. Williamson.

The study is published in the journal Environmental Research Letters.


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