Climate Change The case for carbon farming in California Can farmers and ranchers use plants to capture greenhouse gases?

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Agriculture is responsible for one-third of global carbon emissions, but an increasing number of farmers and ranchers think it can be a powerful ally in the fight to slow climate change, through a set of techniques called carbon farming.

The underlying principle of carbon farming is straightforward: to remove carbon dioxide from the atmosphere, where it drives climate change, and put it back into plants and the pedosphere, the Earth’s living soil layer. One way farmers do this is by fertilizing their lands with nutrient-rich compost. As plants grow, they store carbon in their leaves and roots and bank it in organic matter, such as decomposing plant pieces in the soil. Soil microorganisms, including bacteria and fungi, also store carbon. This prevents the carbon from escaping into the atmosphere and joining oxygen to form carbon dioxide.

Carbon farming has taken hold in California, which is increasingly stepping up as a pioneer of progressive climate policy in the U.S., even as the Trump administration denies the reality of climate change. Today, more than 80 ranchers and farmers in the state are implementing the practice. And the number is likely to increase, since the 2018 Farm Bill includes provisions for a pilot program that gives farmers an incentive to farm carbon.

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Grassland soils naturally absorb and store carbon in soil organic matter, but common agricultural practices, like plowing and tilling, diminish this ability by breaking apart the soil and releasing its stored carbon into the atmosphere. The good news is that carbon can be reabsorbed by the very same soil. Dozens of farming methods, including composting, managed grazing, no-till agriculture and cover crops, are thought to achieve this feat. Many of them mirror age-old, organic farming techniques.

The potential for land-based carbon sequestration in California is significant. Rangelands cover about 56 million acres, half the state’s overall land area. According to The New York Times, if 5% of that soil is treated with compost, the carbon sequestered would offset about 80% of the state’s agricultural emissions, the equivalent of removing nearly 6 million cars from the road. If scaled to 41%, it would render the state’s agricultural sector — now accounting for 8% of the state’s overall emissions — carbon neutral for years. This amount is anything but negligible: California is the most populous state in the U.S. and the country’s second-largest emitter of greenhouse gases. Overall, it’s responsible for 1% of global greenhouse emissions.

Because carbon farming allows farmers to use fewer pesticides and synthetic fertilizers, it’s likely to help cut costs. That means that increasing soil carbon while farming isn’t just possible, but good for business as well.

Still, logistic and economic challenges remain. The up-front cost, for one: While carbon-farming techniques can ultimately save money, the high production costs associated with compost make it quite expensive in the short term. Applying compost in California costs around $700 per acre — more than the majority of ranchers and farmers can afford. California is trying to offset costs by offering ranchers and farmers small grants. With demand currently outstripping supply, there is also the problem of compost availability.

And there are many unknowns — for example, no one really knows how long soil keeps carbon out of the atmosphere. Additionally, climate change itself could be an enemy of carbon farming: As temperatures warm, soils heats up, and soil micro-organisms expel carbon dioxide. The United Nations Intergovernmental Panel on Climate Change, or IPCC, calculates that by 2100, up to 15% of the world’s soil and biomass could become net carbon-emitters.

Ultimately, carbon farming may only pull a limited amount of carbon from the atmosphere. But in California, grasslands appear to be a less vulnerable carbon storage option than fire-prone forests. With global greenhouse gas emissions on the rise, we need to commit to using carbon farming.

Marcello Rossi is a science and environmental journalist. His work has appeared in National Geographic, the Guardian, Al Jazeera, Smithsonian, Reuters, Outside and others. Email High Country News at [email protected] or submit a letter to the editor.