Can Soil Based Carbon Sequestration Make a Climate Difference?

It might if we can figure out how to measure and reward it.
Carbon in the atmosphere, in the form of CO2, is a major contributor to climate change. If we really want to slow down or even stop climate change we need less CO2 in the atmosphere.

There are two ways to reduce the amount of CO2 in the atmosphere, put less in and take more out. We put about 7 Billion metric tons of CO2 into the atmosphere, mostly from transportation, electricity generation, and industry. Reducing greenhouse gas emissions has got to be a priority.

At the same time, there may be ways that we can take carbon out of the atmosphere, and one potentially promising avenue is soil based carbon sequestration, storing carbon in soil. In wild spaces, nature does this naturally. Plants take CO2 out of the air in photosynthesis, grow, and then die. After they have died, the plants start to rot, and some CO2 is released back into the atmosphere, and some becomes part of the natural mulch that supports the next generation of plants.

Natural soil based sequestration works best in colder climates, where the dead plants rot slower. The Permafrost of the arctic region has been a major carbon and methane sink for a long time. A big concern right now that rising temperatures will cause the permafrost to melt, releasing even more greenhouse gasses. But that is a topic for another post.

The increased use of land for agriculture has reduced the carbon sequestered in soil. Deforestation, the conversion of wild grassland to agriculture and practices such as tilling the soil have all resulted in reducing the carbon stored in the soil.

Many environmental scientists are advocated that some of this can be reversed by intentionally changing agricultural practices to increase the amount of carbon stored.

  • Improved Crop Rotations and Cover Cropping
  • Manure and Compost Addition
  • Tillage
  • Conversion to Perennial Grasses and Legumes
  • Rewetting Organic Soils
  • Improved Grazing Land Management

Will this make a difference? Advocates say that at worst, using these methods will improve the health of farm soil and increase land productivity, but there is a cost, and farmers will need to be incentivized to be effective. Now if we are going to incentivize, we need to measure.

Researchers from the Environmental Defense Fund published a paper in the journal Science suggesting a switch to a regional carbon accounting method

A regional accounting and verification framework can help address shortcomings of smaller projects, enabling systemic policy and institutional changes at scale (7). The approach we outline is an adaptation of the jurisdictional approach that is gaining traction for generating credits for tropical forest protection that quantifies emissions reductions relative to a baseline for an entire economic sector across a jurisdiction (7). Most SOC MRV protocols allow for aggregation of field- or farm-based projects; however, how to ensure that fields are appropriately aggregated is rarely defined and is at the discretion of project developers and registries.

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