Iron fertilisation to mitigate climate change?
These light blue smoke-like plumes are phytoplankton in bloom off the coast of Argentina in the South Atlantic Ocean. Phytoplankton plays an important role in iron fertilisation, one of several proposed methods of mitigating climate change known as geoengineering. Geoengineering is the deliberate and extensive intervention in the Earth’s geochemical or biogeochemical cycles with the intent to mitigate climate change. In recent years, understanding of climate change has become widespread in mainstream media. As a result, many mitigation and adaption methods have also been widely publicised along with some interesting, and sometimes frightening, geoengineering proposals. One idea of reducing carbon dioxide in the atmosphere was suggested by oceanographer John Martin. Martin’s iron hypothesis suggested that fertilising the sea with iron could slow global warming by increasing phytoplankton photosynthesis.
It sounds quite simple; at the ocean’s surface atmospheric CO2 is dissolved in sea water. Phytoplankton then absorbs carbon dioxide by photosynthesis turning it into insoluble organic carbon. When phytoplankton dies, dead organic matter sinks to the ocean floor where it gets buried into the geological record and is trapped for aeons. Iron is a trace element all plants need for photosynthesis, hence, by adding iron, phytoplankton blooms can be increased leading in turn to more CO2 being removed.
But is it really that simple? Are iron infusions and boosted phytoplankton activity like this harmful to other organisms? How much added iron is enough and how much is too much? Several studies have examined the effect of spreading finely powdered iron into the surface waters, but very little is known about the side effects. Critics point out that adding iron to the sea could as well favour species that negatively impact other organisms. Other concerns are runaway chemical changes in the surrounding ocean and unforeseeable impacts on marine ecosystems.
Besides, the efficiency of this method is uncertain. It only works if the carbon is actually buried and is not released back into the atmosphere as it could be the case when Phytoplankton is eaten by animals, because their metabolism sends CO2 back into the atmosphere by respiration. So CO2 trapping cannot be guaranteed, as the carbon cycle is not the same for every area and therefore an unpredictable component. Moreover, in many areas growth of phytoplankton is not limited by a lack of iron, thus only certain areas would bloom if iron was added.
Iron fertilisation is still discussed today; the most recent investigations carried out in July 2012 in the North Pacific by the Haida Salmon Restoration Corporation (HSRC) resulted in increased algae growth over 10,000 square miles. The project was controversially discussed as responsible entrepreneur Russ George was accused of having carried out these experiments without permission.
Another important aspect comes alongside geoengineering activities like this in general; ethics. Do we have the right to interfere with sensitive natural processes like this? If yes, where is the limit and who decides how it is done? If no, how do we intend to reduce emissions in a way it really makes a difference?
-Cé
Image Credit: http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17189
http://bit.ly/1s4rtSK
http://www.nature.com/news/ocean-fertilization-project-off-canada-sparks-furore-1.11631
http://www.nature.com/nature/journal/v371/n6493/abs/371123a0.html
Martin, J. H. and Fitzwater, S. E. (1988) Iron-deficiency limits phytoplankton growth in the Northeast Pacific Subarctic. Nature 331, 341-343.