The Natural Fix?

widespread agreement that if current patterns of use, exploita- tion and impacts persist, coastal wetlands will become carbon sources rather than sinks (Hoojier et al. 2006; Jaenicke et al. 2008; Cagampan and Waddington 2008; Uryu et al. 2008; Neely and Bunning 2008; Parish et al. 2008). Duarte et al. (2005) estimate that widespread loss of vegetated coastal habi- tats has reduced carbon burial in the ocean by about 0.03 Gt C per year. Some engineering solutions have been proposed to increase the sequestration potential of oceans. Some, such as ocean fertilization using iron, phosphorus or nitrates, increase the biological uptake of carbon. Others, such as injection of CO 2 into the deep sea, use geophysical stores. The rationale for

engineering the oceans, which are estimated to have a com- bined storage capacity of several thousand Gt C, is to accel- erate the transfer of CO 2 from the atmosphere to the deep ocean, a process that occurs naturally at an estimated rate of 2 Gt C per year (Huesemann 2008). Some researchers warn that these are unlikely to succeed on a global scale, with many questions remaining over the potential ecological side effects, and the direct impacts these may have on local ma- rine life. Large-scale ocean fertilization experiments are pro- ceeding, but it is difficult to determine the quantity of carbon that is actually sequestered on the ocean floor. With too many unknown variables and the current limitations with models, some are urging a cautious approach be taken with any ocean engineering intervention.

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