In 2012, 100 tons of iron sulfate dust and other iron compounds were cast off into a small patch of ocean 300km off Haida Gwaii. It was not a catastrophic accident. Rather, it was completely intentional.
This event was the doing of Haida Salmon Restoration Corporation in an effort to raise the quantity of salmon during the yearly salmon run, a key event for the people of Haida economically. This phenomenon of iron drastically increasing salmon population was first observed in 2010 and was likely caused by a volcanic eruption that occurred two years ago. The eruption had dumped iron rich ash all over the northern Pacific Ocean. Iron is an important element for phytoplankton, as it is a key nutrient needed to synthesize chlorophyll, a key pigment vital for photosynthesis. This paper by Street and Paytan, 2005 suggests that the availability of iron is a determinant of net primary productivity. The resultant increase of phytoplankton could have boosted the availability of food for salmon, causing an increase from 1.7 million fish in 2009 to 34 million in 2010.
Apart from the huge population explosion of salmon, another benefit of fertilising our oceans with iron is that the increase in phytoplankton will increase the intake of carbon dioxide for photosynthesis, effectively locking away the carbon dioxide when they die and sink to the bottom of the ocean. Iron fertilisation is being seriously considered as a geoengineering measure to combat climate change, and with its impressive potential – fertilising the Southern Ocean with iron could result in a carbon capture of one gigaton a year, one-tenth of our yearly carbon emissions.
Fig.1: Phytoplankton bloom in the Barents Sea. Retrieved from National Geographic.
Of course, as with all geoengineering measures, it does not come without its risks. We do not know what the effect on the food web would be were we to massively change the quantity of phytoplankton, the primary source of food for much of ocean life. Furthermore, it took 200 tons of iron to fertilise one square kilometre of ocean in Haida Gwaii. To fertilise the entirety of the Southern Ocean, all 20.33 million km2 of it, may be completely unfeasible. As a comparison, our largest producer of iron, Australia, produced 900 million tons of iron in 2018, less than half of what we would need to fertilise the southern ocean with iron.
Coming back to the events in 2012, though the people of Haida enjoyed another large salmon run the following year, the UN and the international scientific community were understandably pissed. The project had not sought permission from international bodies and may have violated the CBD, and was subsequently described as a rogue experiment. The potential implications of the geoengineering experiment could have yielded unintentional consequences and this brings about the necessity of an international governing body for geoengineering experiments. I still believe that geoengineering research is paramount, but geoengineering should not be considered as a solution until absolutely necessary.
But looking at the direction the world is heading in combating the climate crisis, geoengineering measures may be necessary sooner than later.