Anthropocene Magazine · Climate & nature

Scientists Identify Optimal Locations for Ocean Iron Fertilization to Combat Climate Change

Researchers have found that dumping iron into the ocean to stimulate phytoplankton blooms, a strategy known as ocean iron fertilization (OIF) for carbon dioxide removal, is more effective and less ecologically damaging in higher latitudes than near the equator. The Central Pacific should be avoided due to severe ecological risks, while the Southern Ocean may offer the best balance for carbon sequestration over decadal timescales.

The oceans absorb approximately one-third of human-generated carbon dioxide emissions, prompting research into methods to enhance this capacity. Ocean iron fertilization (OIF) is one proposed solution, aiming to trigger phytoplankton blooms that would draw down atmospheric carbon dioxide. However, the effectiveness and ecological impact of OIF vary significantly by location.

A study published in Nature by the University of California, Irvine team suggests that implementing OIF at higher latitudes, rather than near the equator, could mitigate environmental consequences while still achieving carbon dioxide removal. The Central Pacific is identified as a region to avoid due to substantial ecological risks, whereas the Southern Ocean appears to present a more favorable trade-off between carbon sequestration and ecological risk over extended periods.

While past OIF experiments focused on whether iron limits phytoplankton growth, a climate solution would require larger scales and longer durations, potentially leading to unintended environmental consequences like biodiversity loss and expansion of oxygen minimum zones. These issues arise because added iron can deplete water nutrients, reducing zooplankton populations that are crucial food for marine life.

Using an ocean iron fertilization model, researchers analyzed fertilization potential and ecosystem impact across ten ocean biomes over 60 years. They found OIF could remove up to 5.3 parts per million of carbon dioxide annually. While the Southern Ocean and equatorial Pacific showed the largest plankton blooms, fertilizing the equatorial Pacific led to a significant decline in zooplankton, whereas fertilizing the Southern Ocean resulted in an increase. Future research will explore the fishery impacts of OIF in the Southern Ocean.

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