The Soil-Carbon Connection: an introduction to carbon farming

In the past few years, climate change has evolved from a subject ignored by the general population, to one that now gets daily news coverage. People are increasingly aware of how the destruction of ecosystems and burning of fossil fuels have overloaded our atmosphere with greenhouse gases, which are now increasing the temperature of the planet. In order to have a somewhat stable climate, climate scientists are telling us we have less than a decade to drastically reduce our emissions and work towards removing the excess 250+ gigatons of carbon currently in our atmosphere.

People I talk to are often overwhelmed by this information and are at a loss as to what to do about it. The consequences of climate change are huge, the timeline for creating change is tight, and there isn’t one silver-bullet solution. Thankfully, there are many inspiring people actively researching and implementing solutions. We don’t need to wait for a techno-fix to save the day; many of the tools we need to draw down that carbon and cut emissions already exist and are accessible to many. It’s time to get that knowledge out there and apply these systems on a big scale.

For all us gardeners and farmers, one of the most effective, and sometimes lesser known, systems for capturing atmospheric carbon and cooling the planet is right up our alley – Carbon Farming.

Carbon farming encompasses a range of agricultural practices that remove carbon from the atmosphere and store it in the soil and the biomass of perennial plants and trees. Often included under the umbrella of regenerative agriculture, carbon farming practices not only capture carbon, they also actively improve soil health, produce food, enhance biodiversity, increase farm resilience to extreme weather events, among many other benefits.

If we shift our view of gardens and farmland beyond just sites of food production, we begin to see their incredible potential as landscapes that mimic the services of natural ecosystems and help mitigate climate change. How we treat our soil matters far more than most people know. Whether you are a home gardener, farmer, or food consumer, my hope is that this information will encourage you to adopt or support carbon farming in your area.

In this post, I wanted to give some basic background on soil carbon and explain how conventional agriculture has depleted it. If this is old news to you, and you just want to read about what carbon farming looks like, skip to the last section and stay tuned for future posts.

How Carbon Gets in the Soil

Carbon on it’s own is not a bad thing; all life on earth is based on carbon. At normal levels, with functioning ecosystems, it naturally circulates through the carbon cycle. The conversion of atmospheric carbon into living carbon happens through photosynthesis – the process by which plants take in sunlight, water, and CO2 to produce oxygen and carbohydrates (carbon compounds). Carbon is used by plants for building tissues and feeding the soil food web through root exudates. In healthy undisturbed soils, mycorrhizal fungi take the carbon shared by plant roots and convert it into durable organic compounds that can persist in the soil for decades, preventing that carbon from returning to the atmosphere. Soil organisms transform carbon in dead plant and animal residues into rich humus, which increases soil fertility, feeds the soil food web, and improves soil structure.

Image Credit: Community Environmental Council

Soil organic matter is 58% carbon, so growing practices that build a healthy soil food web and increase organic matter are ones that also happen to be capturing carbon. Soil is one of the planet’s best sites for carbon storage. Terrestrial carbon stores are the second largest carbon storage pool on the planet – over three times more carbon is in the soil than is in the atmosphere, and it has the potential to absorb much more.

Unfortunately, most forms of farming are not building soil carbon, they’re releasing it.

How Agriculture Releases Carbon

Agriculture is currently one of the leading producers of greenhouse gases. The production, processing, and transportation of industrial food comes with a huge footprint. Ecosystem loss and the clearing of land for agriculture is a major contributor, as it destroys the natural systems that absorb and cycle carbon. The fewer functioning ecosystems we have on the planet, the less carbon we can reabsorb into the soil, and the more those greenhouse gases accumulate in the atmosphere. Those ecosystems are also essential to our hydrological cycles, regulating our precipitation and weather patterns, which in turn affect local climate and growing conditions.

Photo Credit: John Lambeth

How the soil is treated and farmed after the land is cleared causes even more emissions. When soil is tilled, soil carbon meets oxygen in the air and returns to the atmosphere as CO2, leading to significant topsoil and nutrient loss. Beneficial fungi are destroyed by repeated tillage and fertilizer use, leading to increased decomposition of organic matter and bacterial-dominated soils that continue to release carbon (bacteria, like us, consume carbon and oxygen, and exhale carbon dioxide). Once that nutrient-rich soil carbon is gone, so too are the life forms that feed on it and the soil becomes lifeless. Conventional agriculture then turns to synthetic nitrogen fertilizers to provide nutrients, which produce nitrous oxide, a greenhouse gas 300 times more potent than CO2 in the atmosphere.

Prairie soils, for example, were once some of the deepest and richest in the world at 6-15% soil organic matter, or more. Many areas that have been industrially farmed for decades are now in the range 0-2%. If you think of that in terms of carbon, the emissions are huge. Tillage-based agriculture, since it’s invention, has caused over 116 gigatons of soil carbon to be released into the atmosphere (that’s almost HALF of the total excess carbon currently in the atmosphere). Most of our food currently comes from industrial-scale, high-tillage, mono-cultures of annual crops, on land which once hosted functioning ecosystems. Throw in greatly mismanaged livestock operations, (dependent on feed from annual high-tillage crops) responsible for 15+% of global greenhouse gas emissions, and it’s apparent that our food systems are at the root of our environmental crises.

This image has an empty alt attribute; its file name is graincrop.jpeg
Photo Credit: Jahoo Clouseau

It’s not just that our agriculture systems are massive emitters of carbon, it’s also that they are fragile. With climate change comes increased rates of extreme weather events. Fields of single-species annual crops in tilled soil are incredibly vulnerable to wind, rain, extreme heat, drought, and flooding. These are the systems we are relying on for all our staple crops in an increasingly turbulent climate. If we don’t change this, our global food supply is at risk.

But there’s good news. Carbon can be taken out of the atmosphere and returned to the soil. There are alternative models of agriculture that are far more resilient. We can approach food production in a very different way that repairs what has been broken.

If our growing practices change, agriculture, in combination with eliminating emissions from fossil fuel consumption, has the potential to be one of the most impactful climate change solutions out there. Agricultural land in the United States alone has the capacity to sequester about 650 million metric tons of carbon dioxide (CO2) every year. It is possible for farms to provide food and resources for people, as well as act as functioning ecosystems that capture large amounts of carbon, restore our hydrological cycles, and increase the durability of our food system in the face of climate change.

Introducing: Carbon Farming

Carbon farming is a way to produce food while also regenerating depleted soils and ecosystems, and drawing down atmospheric carbon. It tends to look quite different from the conventional agricultural systems mentioned above.

Across all carbon farming systems you’ll notice some common themes. The first is obvious – avoid tilling the soil. Carbon farming systems, in order to generate soil carbon and cultivate a healthy soil food web, actively protect the soil through minimal tillage and the use of continuous ground cover, living mulches and cover crops.

Carbon farming also has a strong emphasis on perennial crops. Trees and perennials are far better at storing large amounts of carbon in their roots and above-ground biomass, and perform many more ecological services, such as capturing water and stabilizing soil, than annual crops do. In some areas this can include trees and woody perennials, in others it would include herbaceous perennials in pasture and grasslands where most carbon storage is in the biomass of the root system below ground. Restoring ecosystem functioning and supporting biodiversity are common threads. Ensuring that production methods and crops grown suit the landscape they are on helps to reduce overuse of resources. Carbon farming systems tend to stack functions, finding mutually beneficial ways for crops and elements to work together within the same space in order to increase inter-connectivity and efficiency, much like ecosystems do.

If you follow the links below to each of these systems, you can read how Drawdown Project ranks them based on their rate of carbon capture.

Landscapes that traditionally had some tree cover or forest are suitable for agroforestry, such as the layering of useful and food-producing trees and perennials within the same space (similar principles to food forestry), or tree intercropping/alleycropping, where annuals are grown between rows of taller tree crops. Silvopasture is another form of agroforestry, where livestock are intentionally raised with perennial and tree crops. These trees provide both food and shelter, as well as improved pasture from increased soil organic matter, which reduces the livestock’s need for feed from annual crops. It’s worth noting that silvopasture is considered the most effective of all carbon farming approaches, with the potential to sequester 1.95 tons of carbon per acre, per year.

Drier, more brittle environments are better suited to actively managed grazing, where livestock mimic the constantly-moving herds of wild game that helped build the deep prairie and grassland soils. Diverse perennial pasture and pasture cropping integrate perennials and build soil carbon in ways that provide feed for livestock and obtain multiple yields from one piece of land. In northern areas where melting permafrost is a major concern, research is showing that repopulating the mammoth steppe with large herbivoires helps to keep the ground frozen and preserve the approx. 1.4 trillion tons of carbon stored in permafrost.

Clockwise from top left: apple tree intercropping with annuals, walnut and corn intercropping, cattle oak silvopasture, sheep silvopasture in vineyard, diversified cover crops and hedgerows. Photo credit: AGFORWARD Project

Regenerative and conservation agriculture draw down less carbon if they are exclusively annual crop-focussed systems, but are more easily adopted for conventional farms. These farming methods include continuous ground cover, diversified plantings, crop rotations, minimal tillage, avoiding synthetic pesticides and fertilizers, and building organic matter in the soil. Biochar is also an increasingly popular method of supplying long-term soil carbon on some regenerative farms.

Carbon farming can also encompass changes that don’t directly produce food, but benefit the farm and wider ecosystem. These range from integrating perennial hedgerows and habitat for beneficial insects into the landscape, to putting land aside for water catchment and riparian buffers. Much of the world’s farmland is on drained wetlands, once massive carbon storage sites. Regenerating those wetlands can sequester carbon as well as recharge the water table, filling depleted aquifers and watersheds. Restoring and utilizing degraded lands is key to protecting existing ecosystems and reducing the amount of land cleared to create new farmland.

Perennial biomass crops, used for creating non-food sources of oil and energy, is another way to use degraded land. The downside of this kind of land use is that a large portion of the carbon sequestered re-enters the atmosphere once consumed, though it does prevent fossilized carbon from being introduced to the carbon cycle. Only a small percentage of arable land should be used for biomass crops, to prevent it from using up land that would be suitable for ecosystem restoration and food production.

Depending on climate and soil, each carbon farming system will sequester carbon at a different rate, and some methods are far more impactful than others. There’s still a lot of research needed to look at how these systems work in various settings, and how to optimize them to capture the most carbon. But, considering that conventional agriculture is currently a net-emitter of greenhouse gases, even those systems with low carbon sequestration rates offer important alternatives. If you look through Drawdown’s full list of food-related categories, you can see how widespread changes to agriculture can sequester huge amounts of carbon. What is just as valuable as carbon capture in carbon farming systems, is that they take a whole-system, ecological perspective on food production. Moving away from methods that are purely extraction-based, to ones that value soil health and biodiversity on the same level as yield, is a big paradigm shift that we need to make. It will also determine whether our food systems and ecosystems are resilient enough to provide for us over time in the face of a changing climate.

In future posts, I’ll go into greater depth with each individual carbon farming system, explore their benefits and potential impact, and give examples of farms in temperate climates that are practicing carbon farming. There are ways for home gardeners to take these concepts and use them on a small scale. Climate change and ecological collapse are the biggest issues of our time – the more we understand the grassroots solutions that are out there, the faster we can embrace and implement them.

Great Reads on Carbon Farming:

  • The Carbon Farming Solution: A Global Toolkit of Perennial Crops and Regenerative Agriculture Practices for Climate Change Mitigation and Food Security by Eric Toensmeier
  • Grass, Soil, Hope: a Journey through Carbon Country by Courtney White
  • Carbon Sequestration Potential of Terrestrial Ecosystems by Rattan Lal (https://www.researchgate.net/publication/328809135_The_carbon_sequestration_potential_of_terrestrial_ecosystems)
  • Dirt to Soil by Gabe Brown
  • Drawdown: The most comprehensive plan ever proposed to reverse global warming, edited by Paul Hawken (www.drawdown.org)
  • The Organic No-Till Farming Revolution by Andrew Mefferd
  • Mycorrhizal Planet by Michael Philips
  • Silvopasture by Steve Gabriel
  • Regenerative Agriculture by Richard Perkins
  • Call of the Reed Warbler by Charles Massey
  • Restoration Agriculture by Mark Shepherd
  • Carbon Sequestration Potential on Agricultural Lands: A Review of Current Science and Available Practices (https://sustainableagriculture.net/wp-content/uploads/2015/12/Soil_C_review_Kane_Dec_4-final-v4.pdf)
  • Dirt: The Erosion of Civilizations by David Montgomery

2 comments

  1. Thanks Kim great intro article! Can’t wait to read the next posts. Do you known if there are any certification labels in the works for carbon farmed food?

    Like

    • Glad you enjoyed it, Jacob! I have not heard of any certification out there for carbon farmed food – it’s a pretty new area. There is talk within regenerative agriculture about this, as without a system for verification, anyone can use the term to greenwash their product or farm.

      Like

Leave a Reply to Jacob Cancel reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s