Soil Carbon: Ecosystem Restoration Under our Feet
May 10, 2024, 1:55pm PDT • CARBON ACADEMY
Our climate crisis can basically be summed up like this: we’re burning carbon at a greater rate than plants are removing and storing it through photosynthesis.
The good news? We can reverse that trend — the science of nature-based carbon removals is well-established. Along with drawing down our emissions, we can bring the carbon cycle back into balance through restoration of forests, and by harnessing the incredible power of plants to create carbon biomass.
But there’s another force at play within nature restoration. It’s nearly invisible, and right under our feet: soil.
Soils are the underappreciated and overlooked partner in the photosynthetic process. Just as photosynthesis created the Earth’s atmosphere and oxygenated the planet, life as we know it wouldn’t exist if not for the complex chemical reactions taking place between plant roots, microbes, water, air and tiny mineral particles of eroded rock — all collectively known as soil.
Soil provides the platform for carbon and nutrient cycling. On top of their amazing ability to photosynthesize, plants have also evolved a miraculous and mysterious partnership with an array of microbes to pull nutrients out of the soil through their roots.
At the end of their life, plants in a natural system are cycled back into the soil as they decompose, and the cycle of nutrient flow continues. In this natural nutrient cycle, some carbon exists in a short-term cycle near the soil surface, where decomposing organic matter recycles nutrients and releases CO2. Meanwhile, a longer term accumulation of organic matter takes place deeper in the soil horizon, building long-term soil structure and sequestering carbon through the exchange of sugars between roots and microbes.
Soil profile, Montana. The upper, darker A Horizon contains the majority of organic matter, and is most subject to erosion and disruption from agricultural practices. Over time, soil organic carbon accumulates in the lower horizons.
This entire nutrient cycle is what sustains forests, grasslands, and even deserts — and it’s also what has sustained humanity and our farming systems for the last 10,000+ years.
Soil provides the foundation for a healthy ecosystem, and it’s also an ecosystem within itself.
Minerals, air, and water interact with plants, bacteria, archaea, protists, and all manner of other microbes in a microscopic food web — parallel to the more familiar web of animals, plants, and insects above ground.
And like a forest or other above-ground ecosystem, any changes in these symbiotic elements can have devastating effects. We’re used to thinking of ecological damage on a large scale, such as clear cutting a forest or a landslide. At the soil level, these ecological disruptions could take the form of deep tillage or removing leaf litter.
Over time, we’ve learned modern agricultural practices can unintentionally disrupt these vital carbon and nutrient cycles.
Over the last century, farming and ranching have become industrialized, as agriculture has focused on predictability and yield. Industrialized processes have developed ways to bypass natural processes for plants to gain nutrients. The invention of the Haber-Bosh process, combined with the means for creating chemical fertilizers, has transformed agriculture from a closed loop system into an open-loop system — where nutrients come from external chemical inputs, and plant residues are removed rather than allowed to cycle back into the soil.
*Source: https://www.epa.gov/ghgemissions/understanding-global-warming-potentials
Today, agricultural soils have lost their natural carbon-holding capacity, making agriculture a net producer of greenhouse gas emissions. With agriculture making up 38% of land use globally,1 agricultural lands present an enormous climate challenge — but also an enormous opportunity for restoration and positive climate impact.
How?
These broken cycles can be reversed through the regenerative management of agricultural lands — and soil ecosystems can be restored even while maintaining agricultural production.
Regenerative agricultural principles upend the assumption that growing is inherently extractive — instead, they challenge us to farm and ranch in ways that are not only sustainable, but actually give back to the soil ecosystem and improve soil health.
Regenerative practices include those that:
- Reduce disruption of soil structure, such as conservation tillage
- Build organic matter in the soil by recycling crop residues and planting between seasons (e.g. cover cropping)
- Reduce exposure to erosion, and
- Reduce reliance on chemical fertilizers that also contribute to greenhouse gas emissions
Utilizing nitrogen-fixing species, such as this Cajanus cajan (pigeon pea) as hedgerows and cover crops helps to restore natural nutrient cycles while increasing organic matter and reducing reliance on chemical fertilizers. (Project: Lake Victoria Agroforestry, Trees for the Future.)
And here’s where the Voluntary Carbon Market (VCM) comes into play: by placing a dollar value on the carbon sequestered in soil, projects in the VCM can provide growers and ranchers with the economic means to implement these critical regenerative practices.
A soil core is used to take samples to measure soil organic carbon content and other soil measurements. Soil organic carbon is the vehicle for long term removal of carbon from the atmosphere,and regenerative agriculture has many additional ecosystem and soil health benefits. (Project: Northern Great Plain Improved Grazing, Native. Photo credit: Native)
Soil sample collection in the field, Kenya. Samples will be sent to a lab for analysis on soil organic carbon content. (Project: Lake Victoria Agroforestry, Trees for the Future. Photo: Catona Climate)
Soil samples are tested and analyzed at the lab to determine soil organic carbon content. At the KEFRI (Kenya Forestry Research Institute) lab, lab technicians process samples using the Walkley-Black method. (Project: Lake Victoria Agroforestry, Trees for the Future. Photo: Catona Climate)
Farmers and ranchers motivated to become better land stewards are fighting an uphill battle, trying to reverse decades of deeply-entrenched norms and practices. But carbon credits can function like another “crop” growers can sell — in this case, they yield benefits from working to protect and improve soil health.
When soil carbon and regenerative agriculture projects provide a multitude of opportunities for growers and ranchers — from financing training and education programs to direct monetary assistance and carbon revenue shares — it becomes possible to get even more projects off the ground, which in turn benefits us all in the fight against climate change.
Agroforestry systems mixing annual crops with perennial trees and shrubs reduce soil erosion, improve soil structure, and lead to carbon sequestration deeper in the soil profile. (Project: Lake Victoria Agroforestry, Trees for the Future. Photo: Catona Climate)
A healthy grass root system from regeneratively grazed lands in Montana. Regenerative grazing aims to maximize perennial grass growth and productivity, leading to more robust root systems which in turn leads to improved soil ecosystem function. (Project: Northern Great Plain Improved Grazing, Native. Photo credit: Native and Western Sustainability Exchange)
That’s why Catona’s ’s portfolio of nature-based carbon projects includes several projects working directly with farmers and ranchers.
Regenerative grazing techniques move livestock through smaller pastures, allowing livestock to graze evenly and giving grasses more time to rest and recover. Over time, pastures maintain better groundcover, more diverse species mix, and stronger root systems, all of which improve soil health. (Project: Patagonia Regenerative Grazing, Native. Photo: Catona Climate)
We truly believe that, together over time, we have the power to restore ecosystems — both above ground, and below.
1. FAO Statistics Divisions https://www.fao.org/sustainability/news/detail/en/c/1274219
Megan Bomba
Megan Bomba is the Carbon Program Monitoring & Engagement Director at Catona Climate. Megan has 15 years of experience in social impact project management and pilot implementation, with a focus on community nutrition and food security, market access for farmers, rural development, and monitoring and evaluation of clean cookstoves projects. She holds a B.A. in Environmental Studies from Oberlin College and a Master of Science degree in International Agricultural Development from U.C. Davis.
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