In this deep winter month of January, my thoughts turn to roots and the soil – that mysterious realm that we know so little about. As the seriousness of our climate problems sinks in, we are looking for ways to reduce greenhouse gasses. We can reduce harmful emissions, and we can also remove carbon from the atmosphere in a variety of ways. There are efforts to chemically ‘capture’ carbon dioxide and store it, but the earth already does this naturally through photosynthesis! Many of us are hopeful about the potential of biological carbon sequestration: storing/sequestering more carbon in landscapes, and particularly soil. We have too much carbon in the atmosphere, and the earth’s soil has lost much of its carbon. According to the US Global Change Research Program, North American cultivated soils have lost between 20 and 75 percent of their original top soil carbon. Can we move carbon from the air into the soil in large enough quantities to make a difference? According to one source, soils contain more than twice the amount of carbon stored in the atmosphere. Scientists say that more carbon resides in soil than in the atmosphere and all plant life combined; there are 2,500 billion tons of carbon in soil, compared with 800 billion tons in the atmosphere and 560 billion tons in plant and animal life.
Governments around the world are acting to pull atmospheric carbon into the soil. In 2016 the French government launched the “4 per 1000” program. Based on their research, an annual increase of the world soil organic carbon by 0.4% of its current value would be larger than the earth’s 2015 annual increase in atmospheric CO2. California pays farmers to sequester carbon through California Climate Investments, and the Healthy Soils Initiative makes soil carbon sequestration an integral part of California’s work to be climate neutral by 2045. A California state report found that farms and forests could absorb as much as 20 percent of California’s current level of emissions. Boulder County produced a Carbon Sequestration feasibility study in 2018, and several carbon sequestration studies are underway, including an EcoCycle Citizen Science Project, and a Boulder County Citizen Science Soil Health Project.
Soils can hold carbon because they are alive! For many decades, mainstream agriculture believed that soil was simply a holder of chemicals providing nutrition to plants. In the last couple decades, there has been a revolution in our understanding of soils. We now know that soil is alive: teeming with a vast variety of life. There are more soil microorganisms in a teaspoon of healthy soil than there are people on the earth! This soil life is fed by plants. Remarkably, plants in healthy soils transform much of their energy from photosynthesis into liquids that they release through their roots. These energy dense, nutritious compounds feed a vast network of bacteria, fungi and other plant life, that in turn provide most of the nutrients that the plant needs. In many cases, the soil fungi grow into the plant roots, which can lead to vast root/fungi networks that allow plants to communicate with each other. This soil life holds carbon in the soil in a variety of ways: some storage is short-lived, but it is also possible to form organic compounds that hold carbon for decades. Without carbon and critical microbes, soil becomes mere dirt, a process of deterioration that’s been rampant around the globe. Many scientists say that healthy soil practices can turn back the carbon clock, reducing atmospheric CO2 while also boosting soil productivity and increasing resilience to floods and drought.
Our landscapes can hold carbon in many ways. Biological carbon sequestration includes: plants storing carbon – as tree trunks, prairie grass roots in the soil, or any other part of a plant; holding carbon biologically in the soil; and biochar – a form of charcoal which can last for centuries in the soil. How much can biological carbon sequestration do? Estimates range from sequestering all of the carbon people produce to less than 5 percent. There are great gaps in our understanding of soils and roots.
Despite our lack of knowledge, it is clear that increasing the amount of carbon held in our yards, farms, rangeland, forests and prairies will help all life. Healthy soil, with large amounts of carbon/organic matter and lots of soil life, supports healthier (and more nutritious) plants, holds more water (and helps water penetrate more deeply), and helps landscapes be more resilient in our increasingly erratic climate. Many of the exciting ideas for soil health and soil carbon sequestration come from Regenerative Agriculture, which is focused on healthy soil, and is generally no-till organic farming.
How do we sequester carbon and help create healthy soils in our yards?
- Create gardens dense with plants! Have layers of plantings: Trees above, shrubs below, groundcover on the soil
- Encourage plant roots to grow deeply and vigorously by watering deeply
- In vegetable gardens, use cover crops and inter-planting to keep a continuous cover of plants- never leave bare soil
- Use compost instead of chemical fertilizers. Although compost breaks down and releases its carbon fairly quickly, it can be part of creating healthy soil full of micro-organisms that create long lasting forms of carbon.
This cooperative synergy between plants and soil life inspires me to envision that we are moving from an age where we praise singular heroic actions to an understanding that our strength lies in the rich, mutually enriching, connections we have within our communities. Each of us feeds our community, which in turn feeds us.