Scientists urge caution on ocean iron fertilisation
A group of the world's leading marine scientists has cautioned against selling carbon credits from ocean iron fertilisation. Writing in the journal Science, they argue that the efficacy of the technique as a means of removing carbon dioxide (CO2) from the atmosphere remains unproven, and that too little is known about its wider environmental impacts. They call for more research to answer these questions. Ocean iron fertilisation (OIF) is one of a number of ocean-based methods which has been put forward as a means of mitigating climate change by removing CO2 from the atmosphere. It involves releasing iron into the upper levels of the ocean to stimulate the growth of phytoplankton, which absorb CO2 from the atmosphere for photosynthesis. The theory goes that when the phytoplankton die, they sink to the bottom of the ocean, taking the carbon with them and effectively sequestering it. A number of studies have shown that seeding the ocean with iron can indeed stimulate phytoplankton growth. However, while these experiments taught us a lot about the role of iron in ocean ecosystems and carbon dynamics, they were never intended to test the efficacy of OIF as a carbon mitigation strategy. Furthermore, the biogeochemical and ecological impacts of adding significant amounts of iron to the oceans remain poorly understood. Despite these uncertainties, a number of companies are planning to carry out large-scale iron releases to generate the sale of carbon credits. 'This group feels it is premature to sell carbon offsets from the first generation of commercial-scale OIF experiments unless there is better demonstration that OIF effectively removes CO2, retains that carbon in the ocean for a quantifiable amount of time, and has acceptable and predictable environmental impacts,' the scientists write. 'While we do envision the possibility of iron fertilisation as an effective form of carbon offsetting, we believe larger scale experiments are needed to assess the efficiency of this method and to address possible side effects,' says Professor Andrew Watson of the University of East Anglia, UK, one of the authors of the paper. 'There remain many unknowns and potential negative impacts.' The scientists call for targeted research programmes to address these uncertainties. Field studies on larger spatial and longer time scales are needed, as ecological impacts and CO2 mitigation are scale-dependent. The effects of OIF in high and low nutrient regions should also be considered, along with a broad assessment of the ecological impacts of OIF on ocean biochemistry and the organisms that live there. The paper also highlights the need for long-term monitoring and the use of models to assess effects beyond the study area and the observation period, and improved modelling studies of the results and consequences of OIF. Finally, they call for an analysis of the costs, benefits and impacts of OIF relative to other climate and carbon mitigation schemes. 'We are currently facing decisions on climate regulations, such as the post-Kyoto framework discussed in Bali, carbon cap-and-trade bills in the US Congress, and consideration of OIF by the parties to the London Convention, and we feel that ocean biogeochemical research will help inform these important policy decisions,' the scientists conclude.