Climate change: Reducing the carbon hoofprint

Eating meat is bad for the planet, right? That hamburger you're contemplating for lunch comes from a cow that, most likely, was raised within the industrial agriculture system. Which means it was fed huge amounts of corn.

Cows are less efficient than chickens or pigs at converting corn (or other feed) into body weight. The industrial agriculture system employs 55 calories of fossil-fuel energy to produce one calorie of beef. Meanwhile, livestock production is responsible for much of the carbon footprint of global agriculture, which accounts for at least 25 percent of humanity's annual greenhouse gas emissions.

Despite this, agriculture is invariably overlooked in climate policy discussions. In his 50-minute speech on climate change last week, President Obama did not even mention agriculture except for a reference to how farmers will have to adapt to more extreme weather.

No one has been more influential in popularizing the environmental critique of industrial agriculture than Michael Pollan. His 2006 bestseller, "The Omnivore's Dilemma," revealed how corporate profits, misguided government policies and an emphasis on convenience have given Americans food that is cheap but alarmingly unhealthy for those who eat it, not to mention for the soil, air and water relied upon to produce it.

These days, however, Pollan is delivering a deeper yet more upbeat message, one he shared in an interview while promoting his new book, "Cooked: A Natural History of Transformation." Now, Pollan is suggesting radical new ways to make agriculture work for both people and the planet.

"Technology" is central to Pollan's vision, but why call even seemingly old-school methods "technology"? Because, Pollan says, "technology has so much glamour in our culture, and people only want to pay for technology."

With the right kind of technology, Pollan believes, eating meat can actually be good for the planet. That's right: Raising livestock, if done properly, can reduce global warming. That's just one element of a paradigm shift that Pollan and other experts are promoting. They believe that new agricultural methods wouldn't just reduce the volume of heat-trapping gases emitted by our civilization — they would also draw down the total amount of those gases that are already in the atmosphere.

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 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. It's attracting growing attention as climate change accelerates in the face of continued political inaction. 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 (when a warmer planet boasted sea levels 30 feet higher than today's — high enough to submerge most of the world's coastal capitals). Meanwhile, human activities, from driving gas-guzzlers to burning coal to leveling forests, 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. To be sure, reducing the 2 ppm of annual emissions growth is absolutely necessary — it just doesn't go far enough. At 400 ppm, global warming is already contributing to a mounting litany of record-­breaking weather.

What's more, even if annual emissions of greenhouse gases drop to zero, global temperatures will keep rising and climate impacts keep intensifying for decades to come, thanks to the inertia of the climate system. 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.

We are sure that photosynthesis works. Photosynthesis is a major reason we humans can survive on this planet: 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 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 — comes along and 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."

Pollan emphasizes that switching from corn-fed to properly grazed cows brings other benefits as well. Sequestering carbon improves the soil's fertility and water retentiveness, thus raising food yields and resilience to drought and floods alike.

"It also raises our spirits about the challenges ahead, which is not a small thing."