Fertilizing the oceans with iron could help remove a gigaton of carbon dioxide per year

Iron could massively boost ocean algae populations.
Chris Young
Plankton bloom illumination at night time.
Plankton bloom illumination at night time.


  • Scientists suggest we could fertilize the world's oceans with iron to fight climate change.
  • Iron would lead to phytoplankton blooms, which would help to pull carbon dioxide out of the atmosphere.
  • One "very conservative" estimate suggests a gigaton of carbon dioxide could be removed per year with this method.

Scientists have hatched a plan to flood the world's oceans with phytoplankton in a bid to avoid the worst effects of climate change.

It's a form of geoengineering — focused on the seas rather than the skies — that relies on the ocean's ability to absorb vast amounts of carbon dioxide and naturally dissolve it. Unlike other forms of geoengineering, it doesn't involve harmful chemicals.

Phytoplanktons naturally use carbon dioxide and sunlight for photosynthesis, in the same way as land-based plants, to produce oxygen. In fact, phytoplanktons are actually responsible for approximately 50 percent of the oxygen in our atmosphere.

A new form of geoengineering

Some researchers have proposed that we could increase the amount of phytoplankton in the ocean to allow it to pull more carbon dioxide out of the atmosphere. As phytoplankton thrives in iron-rich areas, small amounts of iron could be added to parts of the ocean to produce a lot more phytoplankton.

Ken Buesseler, a marine radiochemist at the Woods Hole Oceanographic Institution, and a team of scientists investigated the effects of iron fertilization on the world's oceans. They found that the introduction of iron could "alter the flux of carbon to the deep ocean" and that it significantly contributed to the amount of carbon dioxide pulled into the ocean.

However, as Buesseler explained to The Daily Beast, his research was carried out 20 years ago, and the scientific community has done little to investigate the potential of iron fertilization since that time. “What happened 20 years ago is we started going around, and we would spread out a chemical form of iron and look for that phytoplankton — the plant response — and indeed, it really showed very clearly that if you enhance the iron, then you could create more uptake of carbon dioxide,” Buesseler explained. "The difference between now and 20 years ago is that I think the climate crisis is so much more apparent to the public."

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Iron fertilization could remove one gigaton of CO2 per year

Last year, Buesseler joined a group of scientists to release a report through the National Academies of Sciences, Engineering, and Medicine that looked at several options for fighting climate change, including iron fertilization and increasing the levels of phytoplankton in the world's oceans. Buesseler doesn't believe adding iron to the world's oceans on a mass scale to increase phytoplankton levels would cause any harm to global ecosystems. However, he does stress that more research is needed to investigate the effects.

Buesseler explained that up to a gigaton of carbon dioxide could be sequestered on a yearly basis using the phytoplankton method — and this, he told The Daily Beast, is a "very conservative" estimate. “It will change the types of plants and animals that grow, but that is already happening with the changes in temperature and acidity,” he said.

Iron fertilization could be deployed fairly easily and cheaply using boats that would simply have to tip the iron into specifically selected regions — chosen because they are lacking in iron. The iron would also take effect quickly, as phytoplankton blooms can be observed within 24 hours of iron being added to water.

It's important to note that Buesseler doesn't see iron fertilization as an alternative to ending the fossil fuel industry. In fact, in July last year, scientists from the U.S. Center for International Environmental Law wrote that carbon capture was a "dangerous distraction" that could be used as an excuse to slow the transition away from fossil fuel consumption. Still, the method could help to avoid the worst effects of climate change alongside other strategies focused on carbon removal and renewable energy production.

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