Carbon Farming: A Potential End to Climate Change?

We can’t say we weren’t warned. For years, scientists have argued that human civilization must prevent the planet’s average annual temperature from rising by more than 2 degrees Celsius—or face certain catastrophe. Once we pass that critical threshold, according to the Intergovernmental Panel on Climate Change, life on planet earth is going to be a lot less fun. Think droughts, floods, superstorms, food shortages, and widespread extinctions.

Now, as forest fires rage and Delaware-sized chunks break off from Antarctica, scientists have more grim news: We’re going to hit the two-degree mark by the end of this century. Even if we manage to cut carbon emissions drastically, it’s simply too late—with one big caveat. If we can find some way to suck excess greenhouse gasses out of the atmosphere, we may still avert the very worst catastrophes.

Soil holds more carbon than the atmosphere and all vegetation combined.
What’s the best way to do this? That’s still up for debate. A Bill Gates-backed startup, for instance, is experimenting with a factory-like facility that pumps CO2 out of the air, creating carbon pellets that can be buried underground or used for fuel. But a time-honored, low-tech solution may prove to be even more viable. It’s called “carbon farming,” and it’s exactly what it sounds like: using farms not only to grow food, but also to sequester carbon safely in the soil.

In some ways, farmers make unlikely climate heroes. Agriculture is a major contributor to global climate change, since the industry drives deforestation, relies heavily on fossil fuel-powered machinery, and raises methane-emitting livestock by the billions. But farms, when they’re managed properly, can also be formidable carbon sinks.

Think back to biology class: Plants absorb atmospheric carbon dioxide through photosynthesis, releasing oxygen in exchange. As crops grow, carbon is used to build plant tissues both above and below ground—from stems and leaves to seeds and roots, even root hairs and root exudes. Sequestering more carbon by planting more trees is readily recognized as a strategy for fighting climate change. But what happens underground is just as important: Plant materials that are left to accumulate and slowly decompose in the soil contribute to the formation of soil organic matter, a way of storing carbon in the soil over long periods of time.

Given this, you could say that carbon farming is a new perspective on an old idea. Advocates of sustainable agriculture—from backyard organic gardeners to large-scale conventional no-till farmers—have been emphasizing the importance of soil organic matter for decades. Soils high in organic matter tend to be good soils: They are more resistant to drought, less prone to erosion, harbor more beneficial soil organisms, and are generally better at growing healthy crops with fewer synthetic inputs. But soil organic matter is also about 58 percent carbon, which is why the business of building and protecting organic matter in soils has suddenly taken on a whole new level of importance.

From the perspective of global climate change, soils are a major compartment within the planetary carbon cycle, the second-largest pool after the oceans, holding more carbon than the atmosphere and all vegetation combined. Soils aren’t necessarily climate neutral, depending on how they’re managed: they can release additional carbon into the atmosphere through practices like overgrazing and excessive plowing, or soak up atmospheric carbon through practices like agroforestry and conservation agriculture. But when run properly, farms can be powerful tools in the fight against climate change.

Estimates of the “technical potential” of agricultural soils to absorb carbon range from 3 to 8 gigatons (billion metric tons) of CO2 equivalent a year for 20 to 30 years, enough to close the gap between what is achievable with emissions reductions and what is necessary to stabilize the climate. If boosting soil organic matter used to just look like a good way to farm, in other words, building soil carbon now looks like a key to planetary survival.

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