Lauren R. Stevens: Capturing carbon deep in the soil


WILLIAMSTOWN — We know that the oceans sequester carbon. We know that plants do likewise. But we need to pay more attention to soil as a carbon sink, according to Judith D. Schwartz.

Schwartz, a resident of Bennington, Vt, shared her views at a Williams College "Log Lunch" in February. Her 2013 book, "Cows Save the Planet and Other Improbable Ways of Restoring the Soil" (Chelsea Green) hints at redemption for the hamburger, while her article "Soil as a Carbon Storehouse: New Weapons in the Climate Fight" (Yale Environment 360, April 4, 2014), says that part of the solution to climate change lies beneath our feet.

Among the many reasons for not eating hamburgers, some relate to our health. Those related to climate change include the cutting and burning of rainforests to allow more grazing for cows and the general, chewed down and eroded mess that cows can leave their pasture.

Schwarz studied the work of Zimbabwean agronomist Allan Savory, who has attempted to turn that around. His Holistic Planned Grazing, practiced now in several countries, mimics the action of wild ungulates, which he sees as improving grasslands and thereby increasing the carbon retention of the soil. If cows are moved so they don't trample a field to death, their hooves can aerate the soil and press seeds into it, while they contribute manure.

HPG is controversial, however. For instance, those cows are also releasing quantities of methane, a potent greenhouse gas.

Uncontroversial is Schwartz's belief that while the soil contains more carbon than the atmosphere and plant life combined, unsustainable agriculture and development release billions of tons of carbon from the soil into the atmosphere.

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Plants draw carbon from the air. Whatever they don't need they send down to their roots. From the roots and mycorrhizal fungi that extend the roots' reach, the carbon is released into the ground. "Without carbon and critical microbes, soil becomes mere dirt," she has written.

One carbon sink was the tall grass prairie, inhabited by wild grazers, that once existed in this country and in other parts of the world. Only three percent still exists here and the loss has been similar elsewhere. These prairies have the capacity to capture carbon deep down.

While it is important to reduce carbon release, scientists and farmers have paid less attention to capturing carbon in the soil as a means of mitigating climate change. She urges reducing tillage and avoiding chemicals. She recommends replanting and maintaining prairies, generally upgrading depleted agricultural land, planting cover crops; avoiding deforestation and the farming of peat lands.

Biomass should be mulched rather than burned. A process called biochar, however, in which plant life if burned in the absence of oxygen, could provide the needed fertilizer for revitalizing grasslands.

These practices have the potential of storing one-to-three billion tons of carbon annually, compared to the three-plus billion tons released by fossil fuel burning. These practices would have the additional benefits of providing resistance to erosion, floods and droughts — and providing more food for a burgeoning population.

At least, that's how it looks from the White Oaks.

A writer and environmentalist, Lauren R. Stevens is a regular Eagle contributor.


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