Chisholm: Don't muck around with oceans


"NO!" read the first slide in Professor Sallie W. (Penny) Chisholm's IAP talk last Thursday.

The question to her emphatic answer: Should we fertilize the oceans?

To further make her point, Professor Chisholm began her remarks by saying, "I thought of putting that [slide] on and then leaving, but..." But she didn't. Instead, she spent the next hour describing why some people would like to fertilize the oceans by adding iron and why she disagrees.

Proponents believe that fertilizing the oceans would be good for two reasons: it could decrease the amount of the greenhouse gas carbon dioxide in the atmosphere, and it could enhance fish production. In the first case, fertilization would increase the amount of phytoplankton -- microscopic plants. The increased number of plants, in turn, would pull more carbon dioxide from the atmosphere as part of the plants' normal growth.

The second argument says that low amounts of nitrogen in some areas of the ocean limit the amount of fish. Fertilizing the ocean with iron and phosphate, proponents believe, would increase the amount of algae that can turn nitrogen gas from the air into a usable form for marine creatures. More nitrogen means more fish.

Dr. Chisholm, the McAfee Professor of Engineering in biology and civil and environmental engineering, gave several reasons why she disagrees with both arguments. Key among them: we do not know how the system works. "If we start mucking around with the oceans, they will definitely throw us some surprises," she said. For example, fertilization could cause dramatic changes in the food web structure. It could also increase production of other greenhouse gases like methane, "so you could be worse off."

Fertilizing to increase fish production also has major potential drawbacks. "You could get blooms of toxic algae [some species of the nitrogen-fixing kind are toxic], stimulate the production of less valuable fish species, and destroy indigenous fish stocks," Professor Chisholm said.

Her conclusion: The "quick fix" idea that we can find another place to put carbon dioxide "is absolutely the wrong mentality... If you're asking where to put it, you're asking the wrong question. We should focus on decreasing emissions of carbon dioxide into the atmosphere."

Professor Chisholm's talk was part of a series called Environmental Perspectives: Research at MIT sponsored by the Department of Civil and Environmental Engineering and the student group Share a Vital Earth.

A version of this article appeared in MIT Tech Talk on January 13, 1999.


Topics: Civil and environmental engineering, Energy, Environment, Oceanography and ocean engineering, Environment and energy, Biology

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