A policy tool aimed at arresting global warming could potentially wreak havoc on the oceans if it is implemented with no restrictions, warn an MIT professor and colleagues in the Oct. 12 issue of Science.
Carbon trading, a feature of the Kyoto Protocol on Climate Change, would limit abiding countries' emissions of the greenhouse gas carbon dioxide. A country that exceeds its limit could still fulfill its commitment by purchasing "carbon credits" from a country that emits less than its quota.
Carbon credits could also, however, be purchased from commercial industries that have developed ways to remove carbon from the atmosphere. And therein lies the hitch, says Professor Penny Chisholm of the Department of Civil and Environmental Engineering and Department of Biology.
One potential technique for removing atmospheric carbon involves fertilizing the oceans. "Our objections are to commercialized ocean fertilization--the scaled-up consequences of which could be very damaging to the global oceans," wrote Chisholm and co-authors Paul G. Falkowski of the Institute of Marine and Coastal Sciences and Rutgers University, and John J. Cullen of Dalhousie University in Canada.
Small scientific experiments over the last 10 years have shown that fertilizing parts of the ocean increases the number of tiny organisms, or phytoplankton, that remove carbon dioxide from the atmosphere as part of their normal metabolism and growth. Some of those organisms fall to the bottom of the sea, or are eaten and fall to the bottom in fecal matter, essentially moving carbon out of the air and into the deep.
Entrepreneurs watching these developments have concluded that fertilizing large patches of ocean might therefore be profitable if carbon trading is instituted. "Proponents claim that ocean fertilization is an easily controlled, verifiable process that mimics nature, and that it is an environmentally benign, long-term solution to atmospheric CO2 accumulation," wrote Chisholm and colleagues.
"These claims are, quite simply, not true," they continued, refuting each argument in turn within the Science article. For example, ocean fertilization is not easily controlled. "A fertilized patch in turbulent ocean currents is not like a plot of land," they wrote.
Chisholm is particularly critical of claims that ocean fertilization is environmentally benign. "What really surprises me is that they're ignoring the results of years of research on aquatic ecosystems," including the negative effects of nutrient enrichment in lakes and coastal waters, she said.
Chisholm emphasized that she and her colleagues are not against individual experiments in which ocean fertilization is used as a tool for studying the ocean's response to enrichment. Such experiments have already yielded "very exciting results that have contributed to our understanding of the role of the oceans in the global carbon cycle and in regulating climate," she said. However, "we are against the large-scale implementation of ocean fertilization as a carbon sequestration option."
Commercial implementation of ocean fertilization techniques is not imminent, but interest is growing. About seven patents have been filed on different techniques, and at least three small companies have been established. Chisholm herself recently talked to a representative from Mitsubishi Heavy Industries about ocean fertilization. "So many large companies are watching with interest," she said.
Although Chisholm noted that a given company fertilizing a relatively small patch of water would not by itself change the ecology of the oceans, she is afraid of the "slippery slope" that such an action would begin. "If it's profitable for one, it would be profitable for many, leading to exploitation and a classic tragedy of the commons," she said.
"One simple way to avert this potential tragedy is to remove the profit incentive for manipulation of the ocean common. We suggest that ocean fertilization in the open seas, or territorial waters, should never become eligible for carbon credits," Chisholm and her colleagues wrote.
In September 2001, Jagat Adhiya (S.M. 2001) and Chisholm wrote a white paper about this topic for MIT's Center for Environmental Initiatives (now the Laboratory for Energy and the Environment). "Is Ocean Fertilization Worth Pursuing as a Carbon Sequestration Option?" can be downloaded from Chisholm's web site under "publications."
A version of this article appeared in MIT Tech Talk on October 24, 2001.