No efficiency loss when combining land and ocean CDR, study shows

What the study shows

To reach the goals of the Paris Agreement, large-scale CDR application will be needed, which can involve both terrestrial and marine methods. However, it has remained unclear how Earth system feedbacks respond when these methods are scaled up or combined. This study closes an important research gap by using two Earth System Models to simulate different CDR scenarios including both marine and ocean CDR over the 21st century.

Specifically, the team performed 42 simulations under a high-emissions pathway, deploying and scaling up Afforestation/Reforestation (AR) and Ocean Alkalinity Enhancement (OAE) both independently and in combination. The results show that global carbon fluxes scale linearly with increased and combined CDR – meaning that the efficiency of CDR is not compromised by combining land- and ocean-based approaches.

“Our results are very encouraging,” says lead author Yiannis Moustakis. “They suggest that we can design more diverse CDR portfolios including both marine and terrestrial methods without losing effectiveness, despite the emerging Earth system feedbacks. This could help reduce pressure on land systems, which can have severe socioeconomic consequences. To support this process, we urgently need more research also into marine CDR to understand its mitigation potential and environmental impacts. And we must be clear: CDR is no substitute for steep emissions reductions – it’s a necessary complement.”

Why this matters

The findings have major implications for climate policy and CDR strategy design:

• They suggest greater flexibility in choosing and combining CDR options.
• They suggest that there is no trade-off between effectiveness and diversification.
• They allow for  more sustainable land use pathways by integrating marine-based methods, alleviating pressure on land.

The authors emphasize the importance of continued research, especially on marine-based CDR, to better understand its functioning and ecological consequences.

Publication:

Yiannis Moustakis, Hao-Wei Wey, Tobias Nützel, Andreas Oschlies, Julia Pongratz: No compromise in efficiency from the co-application of a marine and a terrestrial CDR method. Nature Communications. https://doi.org/10.1038/s41467-025-59982-x.