July 7, 2013

Commentary: Healing the planet through photosynthesis and carbon sequestration

If we implement wise geoengineering, even eating meat could help tackle the backlog of carbon dioxide in Earth's atmosphere.

By MARK HERTSGAARD

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One method of avoiding carbon release is no-till farming: Instead of plowing, a tractor inserts seeds into the ground with a small drill, leaving the earth basically undisturbed. But in addition to minimizing the release of carbon, a reformed agriculture system could also sequester carbon, extracting it from the atmosphere and storing it -- especially in soil but also in plants -- so it can't contribute to global warming.

Sequestering carbon is a form of geoengineering, a term that covers a range of human interventions in the climate system aimed at limiting global warming. Last month, the amount of carbon dioxide in the atmosphere passed 400 parts per million, its highest level since the Pliocene Epoch 2.6 million years ago. Meanwhile, human activities, from driving gas-guzzlers to burning coal, are increasing this 400 ppm by roughly 2 ppm a year.

The case for geoengineering begins with the recognition that the most widely discussed "solutions" to global warming -- such as riding a bike rather than driving a car and making electricity from wind rather than natural gas -- address only the 2 ppm part of the problem while leaving the 400 ppm part untouched. And that's not enough: At 400 ppm, global warming is already contributing to a mounting litany of record-breaking weather. The only way to possibly reduce impacts in the years ahead is to address what is fundamentally driving them: the 400 ppm of CO2 currently in the atmosphere.

According to Pollan, photosynthesis is "the best geoengineering method we have." It's also a markedly different method than most of the geoengineering schemes thus far under discussion -- like erecting giant mirrors in space or spraying vast amounts of aerosols into the stratosphere to block the sun's energy from reaching Earth. Whether any of these sci-fi ideas would actually work is, to put it mildly, uncertain.

By contrast, we are sure that photosynthesis works. Plants inhale CO2 and turn it into food for us, even as they exhale the oxygen we need to breathe.

What does all this have to do with eating meat? Here's where Pollan gets positively excited. "Most of the sequestering takes place underground," he begins.

"When you have a grassland, the plants living there convert the sun's energy into leaf and root in roughly equal amounts. When the ruminant (e.g., a cow) ... grazes that grassland, it trims the height of the grass from, say, 3 feet tall to 3 inches tall. The plant responds to this change by seeking a new equilibrium: it kills off an amount of root mass equal to the amount of leaf and stem lost to grazing. The (discarded) root mass is then set upon by the nematodes, earthworms and other underground organisms, and they turn the carbon in the roots into soil. This is how all of the soil on earth has been created: from the bottom up, not the top down."

The upshot, both for global climate policy and individual dietary choices, is that meat eating carries a big carbon footprint only when the meat comes from industrial agriculture. "If you're eating grassland meat," Pollan says, "your carbon footprint is light and possibly even negative."

Mark Hertsgaard has written about climate change for outlets including The New Yorker, Vanity Fair, Time and The Nation. A fellow of the New America Foundation, he is the author of six books, including “HOT: Living Through the Next Fifty Years on Earth.”

 

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