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Global Warming: Seeding the Ocean

Briefs
Tracking bar-tailed godwits, painkiller-producing plants; more.

 

NASA

Global Warming
Seeding the Ocean

Decreasing emissions won’t cut it. Most experts agree that to stop global warming we’ll also have to remove vast quantities of greenhouse gases from the atmosphere. One promising, if controversial, scheme involves inducing enormous blooms of CO2-sucking plants called phytoplankton in the Southern Ocean.

These microscopic algae remove carbon from surface waters to make food and grow. Some become dinner for sea creatures like krill, but many die, dragging carbon deep into the ocean as they sink. To grow, phytoplankton need iron, a scarce element in some ocean regions. Artificially fertilizing iron-poor areas triggers phytoplankton blooms, and the Southern Ocean could, in theory, lock up a gigaton of carbon a year—one-eighth of annual global emissions. 

In the coming years private companies like San Francisco–based Climos hope to sequester carbon using ocean iron fertilization and sell offset credits on carbon markets. But environmental groups, including Greenpeace and the Natural Resources Defense Council (NRDC), strongly oppose the technique because it’s unproven and might harm marine ecosystems that are already reeling. And leading ocean fertilization scientists maintain there isn’t enough data yet to show that it’s safe and effective. “We know when iron is supplied in very small quantities, phytoplankton proliferate,” says Kenneth Coale, director of Moss Landing Marine Laboratories. “We don’t know exactly what happens next.”

To find out, in January an international team of scientists took a cruise to the Southern Ocean to conduct the so-called LOHAFEX experiment and, over 10 weeks, dumped 20 tons of iron sulfate into a 115-square-mile area—longer and twice as large as any of the 12 previous experiments. For the first time they’ll track post-bloom activity, measuring phytoplankton’s downward flux and assessing impacts on marine life. The project may thus help determine if the process is justified on a large scale.

Even if it can sequester enough CO2 to make a dent in atmospheric levels, the ecological effect is unknown. “Some people say this is like planting trees in the ocean,” says NRDC senior scientist Lisa Suatoni. “It’s not nearly so simple.” Artificial fertilization favors some types of phytoplankton over others, which could reverberate up the food chain to affect fish and mammals. It will diminish oxygen, potentially causing “dead zones” like those seen in the Gulf of Mexico, where few animals can survive.

For now only legitimate research projects—not commercial ventures—are allowed. An international maritime convention imposed the restriction last year after a now-defunct company, Planktos, announced it would dump iron near the Galapágos Islands to sell carbon-offset credits.

Before the scientific community signs off, long-term studies will have to show the process effectively removes CO2 , locks it in the ocean for a certain amount of time, and has predictable, acceptable environmental impacts. “Nobody is pretending that ocean iron fertilization is going to solve all our problems,” says Richard Lampitt, a biogeochemist at the United Kingdom’s National Oceanography Centre who is involved with LOHAFEX. “It’s not a diversion either. We can and should look at a diversity of options, and this is one of them.”

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