New study questions approach to marine CO2 removal

To limit warming to less than 2°C, both emissions reductions and CDR are required.
New study questions approach to marine CO2 removal

NEW DELHI: A new study throws light on the limitations of the current approaches of removing carbon dioxide from the ocean. Unlike planting trees on the land to evacuate carbon, current approaches like shellfish cultivation or seaweed farming and mangrove forests, etc., for marine carbon removal need further scientific rigour to improve them so as to enrich the climate action toolbox, the research paper said.

It underlines that the limited understanding of basic ocean processes is hindering progress in marine carbon dioxide removal, with the ongoing commercialisation of some approaches being “premature and misguided”.

In a new paper, scientists from the University of east Anglia (UeA), the University of Tasmania’s institute for Marine and Antarctic Studies, Centre National Recherche Scientifique, and the institute for Sustainable Development and international Relations, examined the climatic effectiveness of four ‘nature-based’ techniques using marine biological processes.

These involve shellfish cultivation, seaweed farming, coastal blue carbon - using the restoration of seagrass, salt marsh and mangrove forests - and increasing whale populations through ‘re-wilding’. According to the study, upscaling of these approaches bring other ocean processes into play that could cancel out the effectiveness of the proposed carbon dioxide removal (CDR) approach.

Writing in the journal, environ- mental Research letters, they conclude that while these activities are worthwhile for their non-climatic benefits, they cannot provide a significant contribution to CDR and risk being ‘dead ends’ in terms of meaningful climate mitigation. One of its authors opines that these approaches have given insufficient attention to basic constraints relating to ecosystem functioning and the ocean carbon cycle.

To limit warming to less than 2°C, both emissions reductions and CDR are required. A diverse range of potential approaches have been proposed to achieve billion-tonne annual CO2 removal rates within 30-50 years, with multiple techniques needed to be developed and up-scaled massively to achieve that goal. however, the researchers argue that new methods are being proposed with insufficient checks or balances. This is particularly true for ocean-based CDR, now attracting greater interest as the constraints on land-based methods become apparent. The authors point out that ocean-based approaches are being advocated not only by scientists but also by the private sector, without due diligence on their fundamental science.

“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 need- ed to provide significant climatic benefits,” said co-author Williamson, honorary associate professor at UeA’s School of environmental Sciences. lead author Prof Philip Boyd, of the University of Tasmania’s institute for Marine and Antarctic Studies believe these approaches would cause non-climatic benefits.

“There is a need for better communica- tion of the basic criteria for CDR viability using marine processes. Safety, durability, verifiability and scalability should be used to prioritise relevant R&D funding by Governments, as well as providing checks and balances for policymakers,” said Prof Boyd. The authors raised concerns over the ‘opportunity costs’ — the resources directed at these approaches — which they say could be better invested in reducing emissions, as well as other CDR methods, both land and ocean-based, that are more likely to be safe, sustainable, durable, verifiable, and scalable.

Dr Williamson added: “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.

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