Just Add Iron? The Great Promise of Ocean Fertilisation
Guest Blogger: Radio New Zealand’s Our Changing World environment reporter, Alison Ballance
Last week I interviewed two NIWA scientists – Philip Boyd and Cliff Law – about ocean fertilisation, or iron enrichment. Most of us have heard about this ambitious plan, to help solve global warming by dumping large amounts of iron into the ocean, generating phytoplankton blooms which die and sink, effectively sequestering carbon in the deep ocean. I imagine most people thought as I did: that there is an international cabal of scientists and entrepreneurs who are pushing ahead with experiments to test out this grand theory despite concerns and fears about negative side effects, especially those related to unintended biological consequences.
I came away from the interview reassured on two fronts. First, I had a much clearer understanding of the separation between the science, on the one hand, and the entrepreneurial geo-engineers on the other, who use the publicly available results of that science to their own ends. Secondly, it turns out that iron enrichment is not a cost-effective and practical method to sequester carbon.
Iron is just one of a number of nutrients or trace metals that exist in various limiting quantities in various parts of the world’s oceans. Iron is very abundant, but as Dr Boyd explained to me it is also very ‘promiscuous’ – this non-chemist’s understanding is this means it attaches very easily to all sorts of other stuff, thus rendering itself unavailable. The iron-poor parts of the world’s oceans are those the furthest from land, and thus from the source of iron-rich dust. In the late 1980s scientists noted an intriguing correlation in Antarctic ice cores between carbon dioxide and iron – low iron levels preceded times of high carbon dioxide, whereas rising iron levels lead to lowering carbon dioxide. American scientist John Martin is said to have made the connection between high levels of iron and high levels of ocean productivity, apparently quipping ‘give me half a tanker of iron and I’ll give you the next ice age’.
Since the mid 1990s there have been 12 international experiments testing the idea that adding iron to iron-poor areas of ocean will generate phtyoplankton blooms and interact with the atmosphere to remove carbon dioxide. These experiments have had widely varying results, and a recent synthesis to assess whether ocean fertilisation can offer a safe, cost-effective way of sequestering carbon pretty much says it doesn’t. As far as scientists like Boyd and Law are concerned, the experiments have gone as far as they can in answering fundamental questions about connectivity between ocean and atmosphere processes.
Despite the lack of scientific support for the idea, several commercial companies still appear to be pursuing the concept of wide-scale iron enrichment, although quite how this would be funded remains uncertain. One thing that has become apparent is that there is a lack of international legislation covering large scale iron fertilisation or other ocean enrichment activities, and moves are being made to address this under the London Convention (to give it the full name: the “Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter 1972”, which is one of the first global conventions to protect the marine environment from human activities and has been in force since 1975).
I came away from the interview with a clear sense that iron enrichment is not the panacea that will conveniently let us off the hook of controlling our escalating carbon emissions, and reassured that, in this instance at least , there is no ‘evil conspiracy’ between science and industry.
You can listen to Alison Balance’s t interview with Drs Law and Boyd here http://www.radionz.co.nz/audio/national/ocw/2009/06/04/iron_fertilisation