Geoengineering: a sea change

Could dumping iron in the ocean help to address the climate-change crisis? Or would it make a bad situation worse?

What’s the big idea?

Fertilising parts of the ocean with large quantities of iron would produce huge blooms of plankton that eat carbon dioxide, thus reducing the greenhouse effect.

How would it work?

Iron would be dumped in parts of the ocean that have relatively low levels of the element. After the plankton has bloomed, say the scheme’s proponents, it would sink to the bottom of the ocean, sequestering the carbon it had absorbed under the waves.

What are the risks?

Although the idea has been tested on a small scale, it is not yet known if there would be side-effects in trying to fertilise a large part of the ocean. For example, some scientists think that large plankton blooms could release other greenhouse gases, including methane and nitrous oxide.

It is also likely that encouraging huge blooms of plankton would have significant and unpredictable effects on ecosystems. Green group WWF warns that other trace metals could be introduced into the ocean at the same time, some of which might be toxic to marine life.

Early attempts to make money from this scheme have thus-far failed, but considerable interest in the idea has led a number of scientists to seek a ban on profiting from ocean fertilisation, until it has been proven that it removes carbon dioxide from the atmosphere for a “quantifiable amount of time”.

Our verdict

Ocean ecosystems are already under severe pressure as a result of over-fishing and acidification, which is caused by the absorption of too much carbon-dioxide. It seems dangerous to proceed with an idea that might cause further damage to one of our most precious resources. On the plus side, the project is less costly than some other schemes, and more controlled testing could be warranted.

NEXT: smoke and mirrors … in space

Homepage image by Philipp Assmy, Alfred Wegener Institute
Plankton three weeks after iron fertilization.