Ecologists promote carbon farming to stem climate change

Peggy Rathmann and John Wick on their Marin County ranch
(New York Times photo by Jonno Rattman)

UPDATE: For a study on loss of carbon storage capacity in the Midwest, with a map showing cropland expansion, click here.

A deep-dive story from a California ranch illustrates the the role grazing animals can play in improving soil and slowing global warming, Moises Velasquez-Manoff reports for The New York Times.

Children's author Peggy Rathmann and her husband John Wick moved to a 540-acre ranch in Marin County, California, in 1996. It's dairy country, and herds of cows roam the hills, but the couple loved watching deer and other wild animals on their land, so they decided to help it return to a more pristine state by banning a nearby rancher's cows from their land.

But "within months of the herd's departure, the landscape began to change. Brush encroached on meadow. Dried-out, uneaten grass hindered new growth. A mysterious disease struck their oak trees. Their land seemed to be losing its vitality," Manoff reports. "Wick was especially bothered by the advance of a prickly, yellow-flowered invasive weed called the woolly distaff thistle. He pulled it, mowed it, doused it with herbicides. But the distaff kept moving into what had been pasture."

Rangeland ecologist Jeff Creque urged them to invite the cows back: grasslands and grazing animals evolved together, he told them. Grasslands depend on animals to get rid of dead growth and recycle nutrients with manure and urine, so grazing can restore the land if done right. That means allowing cows to roam in herds like wild buffalo, never staying in one place too long. But if the cows are confined to a smaller area for a few months, the land is more likely to suffer.

Creque's advice was proved sound after Wick and Rathmann welcomed cows back to their land the next summer. By the fall, the cows were fat and the land was lush and abundant with wildlife. Creque explained to them that the fat came from carbohydrates in the grass, which came from carbon pulled from the atmosphere. Though most of the carbon humans add to the air is from power and heat generation, agricultural and other land use contributes almost as much."The erosion and degradation of soil caused by plowing, intense grazing and clear-cutting has played a significant role in the atmospheric accumulation of heat-trapping gasses," Manoff reports. "Since the start of the Industrial Revolution, agricultural practices and animal husbandry have released an estimated 135  gigatons -- 125 billion metric tons -- of carbon into the atmosphere."

In recent years, scientists have increasingly advocated trapping more carbon in soil and ecosystems by better land management practices instead of synthetic fertilizers, an idea known as carbon farming. University of California Berkley ecologist Whendee Silver tested the soil on Wick and Rathmann's ranch and found that inviting the cows back had increased the carbon trapped in the soil dramatically. Wick has become an outspoken carbon-farming advocate, and in 2008 founded the Marin Carbon Project along with Creque and Silver. Its goal is to develop science-based carbon-farming practices and establish incentives that will encourage farmers to adopt them.

What about the greenhouse gases from cattle manure? Silver has found that spreading a mixture of manure and compost on fields increases the capture of carbon in the soil, but "No one really know if the carbon they put in the ground more than offsets the methane produced by their cows," Manoff reports. "What they do demonstrate is that augmenting soil carbon while farming is not only possible, but also beneficial, even in a business sense."

States like Hawaii, Maryland, Massachusetts, New York, Colorado, Arizona and Montana are considering or have passed legislation encouraging carbon-farming, but California has led the way. "By 2050, the state aims to reduce greenhouse-gas emissions to 20 percent of what they were in 1990. Nearly half its 58 counties have farmers and ranchers at various stages of developing and implementing carbon-farming plans," Manoff reports. Many of those efforts in California owe a debt to the Marin Carbon Project.