Ocean iron fertilization may amplify climate change pressures on marine animal biomass for limited climate benefit

• Published in: Global change biology 2023-09, Vol.29 (18), p.5250-5260
• Main Authors: Tagliabue, Alessandro, Twining, Benjamin S., Barrier, Nicolas, Maury, Olivier, Berger, Manon, Bopp, Laurent
• Format: Article
• Language: English
• Subjects: Amplification; Animals; Atmospheric models; biogeochemical cycles; Biogeochemistry; Biological fertilization; Biomass; Carbon dioxide; Carbon Dioxide - analysis; Carbon dioxide removal; Carbon sequestration; Climate Change; Drawdown; Ecosystem; Ecosystem models; Emissions control; Environment models; Environmental impact; Environmental Sciences; Exclusive economic zones; Fertilization; Fisheries; Global warming; Iron; Livelihoods; Marine animals; marine carbon dioxide removal; Marine ecosystems; Marine organisms; Nutrient transport; Nutrients; ocean iron fertilization; ocean net primary production; Oceans and Seas; Respiratory disorders; Stratification; Trophic levels; Tropical environment; Tropical environments; Upper ocean
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.16854

Climate change scenarios suggest that large‐scale carbon dioxide removal (CDR) will be required to maintain global warming below 2°C, leading to renewed attention on ocean iron fertilization (OIF). Previous OIF modelling has found that while carbon export increases, nutrient transport to lower latitude ecosystems declines, resulting in a modest impact on atmospheric CO2. However, the interaction of these CDR responses with ongoing climate change is unknown. Here, we combine global ocean biogeochemistry and ecosystem models to show that, while stimulating carbon sequestration, OIF may amplify climate‐induced declines in tropical ocean productivity and ecosystem biomass under a high‐emission scenario, with very limited potential atmospheric CO2 drawdown. The ‘biogeochemical fingerprint’ of climate change, that leads to depletion of upper ocean major nutrients due to upper ocean stratification, is reinforced by OIF due to greater major nutrient consumption. Our simulations show that reductions in upper trophic level animal biomass in tropical regions due to climate change would be exacerbated by OIF within ~20 years, especially in coastal exclusive economic zones (EEZs), with potential implications for fisheries that underpin the livelihoods and economies of coastal communities. Any fertilization‐based CDR should therefore consider its interaction with ongoing climate‐driven changes and the ensuing ecosystem impacts in national EEZs. Our paper looks at the effectiveness of ocean iron fertilization (OIF) in a changing climate (CC) and the impacts of marine ecosystems. We find OIF has a limited potential to be a significant marine carbon dioxide removal mechanisms and amplifies impacts of CC on tropical and subtropical ocean ecosystems.