A new study in Nature models ocean iron fertilization (OIF) across ten biomes over 60 years, finding that the Southern Ocean offers the best balance of carbon removal efficiency and lower ecological risk. Equatorial Pacific fertilization, while efficient, depletes macronutrients, expands oxygen-minimum zones, and reduces macrozooplankton biomass. The study estimates net CDR of 1.1 to 5.3 ppm, with over half re-emitted within decades after fertilization stops. The research highlights regional disparities that complicate carbon crediting and governance. Southern Ocean fertilization shows higher resilience and lower ecosystem perturbation compared to equatorial regions. The authors propose three tiers of risk and efficiency, with the Southern Ocean as the preferred option. The findings underscore that local interventions have global consequences, raising equity concerns for any future OIF deployment.
