‘Fertilizing' Ocean With Iron Still Uncertain Way to Reduce Greenhouse Gases, U.N. Says

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Source:  Daily Environment Report: News Archive > 2011 > February > 02/02/2011 > News > Climate Change: ‘Fertilizing' Ocean With Iron Still Uncertain Way to Reduce Greenhouse Gases, U.N. Says

22 DEN A-7

Climate Change

‘Fertilizing' Ocean With Iron Still Uncertain Way to Reduce Greenhouse Gases, U.N. Says

Small-scale experiments in “fertilizing” oceans with iron have shown varied success in increasing oceans' uptake of carbon dioxide from the atmosphere, and the long-term effects of a larger program are difficult to predict, a United Nations report said.

The report, Ocean Fertilization: A Scientific Study for Policy Makers, was commissioned by the United Nations Educational, Scientific, and Cultural Organization's Intergovernmental Oceanographic Commission. The report was published at the end of January on UNESCO's website.

Oceans are a natural carbon sink; they decrease carbon dioxide in the atmosphere by absorbing it in large part through phytoplankton. Ocean fertilization is the process of increasing iron and other nutrient content in the ocean to increase growth of the microscopic marine plants to both increase the uptake of carbon dioxide from the atmosphere and, ideally, to sequester the carbon dioxide for extended periods of time.

Due to uncertainties about the consequences of fertilization on ocean ecosystems, fertilization in non-coastal waters is prohibited under the Convention on Biological Diversity until stronger scientific justification can be produced and the practice can be assessed by a global regulatory mechanism.

The report was published in light of efforts to develop a regulatory system through the London Convention on Ocean Dumping under its London Protocol (52 DEN A-7, 3/19/10.

Diminishing Expectations

The report noted that over the last two decades, expectations have diminished about the role ocean fertilization could play in significantly reducing atmospheric carbon dioxide.

“Estimates of the overall efficiency of atmospheric CO₂ uptake in response to iron-based ocean fertilization have decreased greatly (by 5-20 times) over the past 20 years,” the report said. “Although uncertainties still remain, the amount of carbon that might be taken out of circulation through this technique on a long-term basis (decades to centuries) would seem small in comparison to fossil-fuel emissions.”

The report looked at several small-scale ocean fertilization experiments and models for predicting long-term consequences. The experiments displayed a wide range of carbon uptake and did not provide sufficient information about what happened once the blooms of phytoplankton caused by the fertilization diminished.

“The experiments to date show that the biological and chemical responses to nutrient fertilization are variable and difficult to predict,” the report said. The increased carbon dioxide uptake also could affect the ocean's ecosystem through increased acidification.

Additionally, the report called for more research into methods for verifying the increased uptake brought about by fertilization and highlighted the need for greater understanding of the potential for reversal, with the absorbed carbon dioxide being released back into the atmosphere.

By Leora Falk

The report,Ocean Fertilization: A Scientific Study for Policy Makers, is available athttp://unesdoc.unesco.org/images/0019/001906/190674e.pdf.