Carbon farming is a zero-risk strategy for curbing climate change
© Cornell University Soil Health Program

Now that 195 nations, including the U.S., have agreed to ambitious greenhouse gas emission reductions to slow the pace of climate change, the question everyone is asking is: How will we actually meet our targets set for 2035?

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Given past performance, many don't think we will get there without so-called "geoengineering" solutions, such as blasting sulfur dioxide or other particles into the atmosphere to shade the planet and compensate for the warming effect of greenhouse gases. Clever, eh? Maybe not. Some recent modeling studies show these seemingly easy fixes could backfire in catastrophic ways, such as disrupting the Indian monsoon season and completely drying out the Sahel of Africa. Another risk is atmospheric chemical reactions that deplete the ozone layer. Do we really want to run global-scale experiments for 20 or 30 years and see what happens?

There is another way, one that is zero-risk and builds on something farmers around the world are already motivated to do: manage soils so that a maximum amount of the carbon dioxide plants pull out of the air via photosynthesis remains on the farm as carbon-rich soil organic matter. "Carbon farming," as it is sometimes called, is Mother Nature's own geoengineering, relying on fundamental biological processes to capture carbon and sequester it in the soil, carbon that would otherwise be in the air as the greenhouse gas, carbon dioxide. 

Over the past century soils worldwide have been degraded due to expansion of agriculture and poor soil management. Today, there is a revolution in agriculture that recognizes the importance of building "healthy" soils by replacing the organic matter that has been lost over time. One way to do this is to use carbon- and nutrient-rich organic sources of fertilizers such as manure or compost rather than synthetic chemical fertilizers. Another is to include carbon- and nutrient-rich crops like legumes (e.g., peas, beans) in rotations, and plant winter cover crops that contribute additional organic matter in the off-season. We've also discovered that reducing the amount of plowing and tilling of the soil ("conservation tillage") slows the microbial breakdown of organic matter that leads to carbon dioxide emissions from soils.

Building healthy soils is essential to ensure food security in the decades ahead in the context of a changing climate. Soils high in organic matter have better water and nutrient retention, which buffers crops from drought and reduces costs for irrigation and fertilizer. Healthy soils also drain more quickly, allowing farmers to get into the field sooner after heavy rains for planting or harvesting.

But can carbon farming really slow the pace of climate change? Some estimate that implementing soil conservation practices on cultivated lands could offset as much as one-quarter to one-third of the annual increases in atmospheric carbon dioxide for a period of time, perhaps buying us 20 to 50 years of benefit as soil carbon stocks are gradually replenished. Others have argued that a 5 to 10 percent offset benefit is more realistic, but even those lower numbers are significant.

Agriculture and soil carbon were not part of the formal climate agreement signed in Paris, but the issue gained stature as a new initiative was put forward by the French minister of agriculture calling for a global 0.4 percent increase in soil carbon stocks each year. The so-called "4 per 1,000" initiative is supported by over 100 partners including national, regional and local governments; companies; research organizations; and environmental groups. While its promoters admit this is not a realistic target for every country, the plan draws attention to the potential contribution of agriculture.

If carbon farming is expanded to consider management of our natural landscapes as well, the potential for carbon sequestration goes up substantially because of the huge quantity of carbon stored in the biomass of trees and deep-rooted grasslands. Deforestation worldwide currently contributes about 17 percent of annual carbon dioxide emissions associated with human activities, so slowing this down would have a major impact. The U.S. Department of Agriculture recently launched "10 Building Blocks" to reduce emissions from agriculture and forestry by 2025 and create incentives for carbon sequestration, but questions about implementation remain. Several U.S. efforts designed for protecting wildlife habitat and biodiversity, like the Conservation Reserve Program, promote land management activities that are complementary to goals of increasing land carbon stocks, but could be redesigned with more emphasis on monitoring and incentivizing carbon sequestration.

While no options on the table will combat climate change single-handedly, including agriculture and forestry in the mix provides a low-cost, zero-risk approach that has well-established benefits. We need to invest in the power of carbon farming to conserve soil and water resources, protect biodiversity and build the resilience of our farms to climate change so we can continue to address the food security challenges of the 21st century.

Wolfe is professor of plant and soil ecology in the School of Integrative Plant Science at Cornell University and chair of the Atkinson Center for a Sustainable Future's Climate Change Consortium. Views expressed in his column are his alone and do not represent those of these institutions.