The case for ocean iron fertilization field trials

Solving the climate-ocean crisis requires both cutting emissions and pursuing carbon dioxide removal (CDR). Past ocean iron fertilization (OIF) experiments in some parts of the ocean have shown that small additions of iron can enhance phytoplankton growth and CO 2 drawdown. However, prior experiments did not assess the efficacy, durability, or feasibility of OIF for CDR, and broader ecological and biogeochemical responses were not evaluated given the short duration and limited spatial scales. The next generation of OIF field trials must be larger (ca. 1000 km 2 ) and longer (>3–6 months) to observe the full response and return to baseline conditions. Potential risks will be assessed, while using community engagement and co-design to create go/no-go decision points. Planning and extrapolating impacts on regional and global scales will require modeling, with the overall goal to provide unbiased assessments and open-source protocols that can guide responsible and rigorous decision-making for any further OIF.