Yet Another Geoengineering Scheme, Ocean Iron Fertilization, Could Backfire

Can we save the planet by ruining it (even more)? Argonne National Laboratory reports that “A new study on the feeding habits of ocean microbes calls into question the potential use of algal blooms to trap carbon dioxide and offset rising global levels.”

Four years ago, the journal Nature published a piece arguing that “fertilizing the oceans with iron to stimulate phytoplankton blooms, absorb carbon dioxide from the atmosphere and export carbon to the deep sea — should be abandoned.”

Now Argonne Lab reports so-called iron fertilization “may have only a short-lived environmental benefit. And, the process may actually reduce over the long-term how much CO2 the ocean can trap.”

The more you know about geo-engineering, the less sense it makes (see Science: “Optimism about a geoengineered ‘easy way out’ should be tempered by examination of currently observed climate changes”). The most “plausible” approach, massive aerosol injection, has potentially catastrophic impacts of its own and can’t possibly substitute for the most aggressive mitigation — see here. And for the deniers, geo-engineering is mostly just a ploy — see British coal industry flack pushes geo-engineering “ploy” to give politicians “viable reason to do nothing” about global warming.Geoengineering is a problem in search of a problem. As the NY Times reported in 2011:

At the influential blog Climate Progress, Joe Romm, a fellow at the Center for American Progress, has made a similar point, likening geo-engineering to a dangerous course of chemotherapy and radiation to treat a condition curable through diet and exercise — or, in this case, emissions reduction.

You can find my previous writings on geo-engineering here. See in particular Martin Bunzl on “the definitive killer objection to geoengineering as even a temporary fix.”


Geo-engineering is a “smoke and mirrors solution,” though most people understand that the “mirrors” strategy is prohibitively expensive and impractical. One of the few remaining non-aerosol strategies still taken seriously by some is ocean fertilization. But it is no better than the rest

As the 2009 Nature piece explained:

The intended effect of ocean iron fertilization for geoengineering is to significantly disrupt marine ecosystems. The explicit goal is to stimulate blooms of relatively large phytoplankton that are usually not abundant, because carbon produced by such species is more likely to sink eventually to the deep ocean. This shift at the base of the food web would propagate throughout the ocean ecosystem in unpredictable ways. Moreover, nutrients such as nitrogen and phosphorus would sink along with the carbon, altering biogeochemical and ecological relationships throughout the system. Some models predict that ocean fertilization on a global scale would result in large regions of the ocean being starved of oxygen, dramatically affecting marine organisms from microbes to fish. Ecological disruption is the very mechanism by which iron fertilization would sequester carbon.

Argonne’s study finds another problem — ocean iron fertilization may have no positive climate impact and might even make things worse:

These blooms contain iron-eating microscopic phytoplankton that absorb C02 from the air through the process of photosynthesis and provide nutrients for marine life. But one type of phytoplankton, a diatom, is using more iron that it needs for photosynthesis and storing the extra in its silica skeletons and shells, according to an X-ray analysis of phytoplankton conducted at the U.S. Department of Energy’s Argonne National Laboratory. This reduces the amount of iron left over to support the carbon-eating plankton….

Rather than feed the growth of extra plankton, triggering algal blooms, the iron fertilization may instead stimulate the gluttonous diatoms to take up even more iron to build larger shells. When the shells get large enough, they sink to the ocean floor, sequestering the iron and starving off the diatom’s plankton peers.

Over time, this reduction in the amount of iron in surface waters could trigger the growth of microbial populations that require less iron for nutrients, reducing the amount of phytoplankton blooms available to take in CO2 and to feed marine life.

If only there were a way to prevent catastrophic global warming that didn’t risk making things worse ….

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