This study analyzes the potential of ocean afforestation, specifically using the Great Atlantic Sargassum Belt (GASB) as a natural analogue, for carbon dioxide removal (CDR). The authors find that biogeochemical feedbacks, such as nutrient reallocation and calcification, significantly reduce CDR efficacy. Atmospheric CO2 influx after CO2 fixation by Sargassum is slow, potentially hindering CDR verification. Furthermore, increased ocean albedo due to Sargassum could influence climate radiative forcing more than Sargassum-CDR. The analysis highlights the complex Earth-system feedbacks affecting ocean afforestation's efficacy.

Lennart T. Bach, Veronica Tamsitt, Jim Gower, Catriona L. Hurd, John A. Raven, Philip W. Boyd