The notion of carbon "sequestration" in soils corresponds poorly to the way carbon cycling works, to the biophysical realities we can sometimes observe. Carbon is constantly moving in and out of soils, though at different rates for different fractions or types. Carbon flows from the air to soil and back again with many subcycles and eddies, some of which remain uncharted, all with enormous local variations.
Trying to use soils as a landfill for atmospheric "pollution" brings a host of troublesome questions. Is it permanent? Does it contribute emissions elsewhere? Would it have happened without the intervention of policy? Fixes for the fixes. When we attempt to manage against what we don't want in complex situations, as with climate and fossil fuel emissions, we guarantee conflict, backlash, cost overruns, and ineffectiveness.
"Sequestration" of carbon in soils is also difficult to measure over large areas, leading to a reliance on modeling and predictions from limited experiments. The effects of a predicted tonnage or rate of soil sequestration, moreover, are difficult to translate into atmospheric change because of the buffering effect of the ocean and many other factors.
Carbon is not just a thing, but a complex--and complicated--chemical eddy in the flow of sunlight energy. We could think of the soil carbon opportunity differently, as the possibility of an investment in biological work and power, as an investment in a process rather than the imprisonment of a substance. We could and should slow the carbon cycle or circle of life, not stop it.
Recognizing investment is also much easier than quantifying sequestration. You can know if it's working or not by sustained increases in soil carbon, water infiltration, and year-round photosynthesis and production without increasing inputs from nonrenewable energy. Biomass and litter cover can be reinvested in the form of surface litter, more absorption and retention of rainfall, and habitat for soil aggregate formation.
Policy to support, reward, or recognize this kind of investment, and tying it to some actual results, may be simpler than paying for sequestration. But the simplest and cheapest policy moves would be to recognize the extent to which we are investing in the problem, either with public funds, institutions, and policies, such as crop insurance, tax rules, and lending policies that subsidize bared soil, and all the costly water problems that result.
Divestment or opting out can be a more powerful strategy for dealing with what we don't want than head-on opposition, which tends to excite and maintain resistance as well as estrange people from what they want and need.
Recognizing the extent to which we invest in soil degradation and water problems, and recognizing actual, demonstrated opportunities to invest in biological power and work, is the purpose of the Atlas of biological work that I've been working on lately.
Soil Carbon Coalition is a 501(c)3 nonprofit organization