MarkAt sustainably FED we love soil carbon. There are more posts on the organic part of dirt on this site than on any other topic. Peruse a few of them, and the reasons for our passion are clear.
- Fixing climate with soil carbon has a big bonus
- More carbon in the soil than in the atmosphere
- Soil matters—graphs that should scare the pants off you
- Comment | A challenging ecological reality
Soil without carbon becomes inert and fails to support plant growth.
Carbonless soil can only be productive through a host of energy-intensive inputs. Even slight losses of carbon reduce the ability of soil to hold water, transfer nutrients and maintain plant production.
When soil is at or near its carbon potential, its ecology is efficient and resilient relative to the local environmental conditions. Even at the extremes, plants can grow, water is stored, and biodiversity is prolific.
In a world that needs every acre of land to support humans with food and ecosystem services, the soil has to be at or near its carbon potential, or we are screwed.
Healthy, biodiverse and carbon-rich soil is ideal.
The truth is starker. Most agricultural soil is depleted in carbon mainly because, for the past 100 years, it has been cheaper to grow food with inputs than by managing the innate production supported by soil carbon. That’s the fossil fuel pulse added to soil as fertiliser, pesticides, herbicides and ploughing with tractors.
And it is cheaper to grow food this way. Farmers find it more accessible—although not easy—and more profitable than the old ways of gleaning what they can from nature.
Consumers like it because their food is cheaper from intensive production systems.
From trawling through the science prepared and delivered by hundreds of global experts and from our practical experience working with soils from Nairobi to Narrabri, we know that soil carbon is essential for food production when the oil runs out or the inputs become too expensive.
Many farms will be forced to go green by reducing inputs and reverting to reliance on soil carbon because they would otherwise go out of business.
Some might for a while.
But the food demand will still be there and opportunity is a powerful human motivator and production will start again. Fortunately, the ways to build carbon into soils are as well known as the ways it is lost. As they already exist, we do not need to scramble for the research findings.
At the most superficial level, the farming system needs to deliver a net excess of production over decomposition so that soil can accumulate carbon.
Here is how senior soil biology researchers describe it
The carbon contained in SOM is the result of a dynamic balance of plant-derived C added to soil as organic residues and C losses from SOM, primarily as CO2 respired by the soil biota. Gains or losses of soil organic C stocks reflect either a net uptake of CO2 (via the plant) or a net release of CO2 from/to the atmosphere. Thus, soil carbon sequestration can be achieved by increasing plant C inputs to soils, storing a larger proportion of the plant-derived C in the longer-term C pools in the soil, or by slowing decomposition.
Alexander, P., Paustian, K., Smith, P., & Moran, D. (2015). The economics of soil C sequestration and agricultural emissions abatement. Soil, 1(1), 331-339.
Practically this means keeping vegetation on the soil through combinations of cover crops, perennial crops, agroforestry and pasture cropping—these tactics add carbon but also slow down mineralisation.
Adding organic manures can help, although these need to come from somewhere and it is harder to make the process circular.
Reducing soil disturbance through minimum or no-till cultivation is usually a good thing for soil carbon accumulation, but sometimes it costs too much in lost yields from weeds and compaction.
Reduced rates of decomposition can happen by lowering the rate of physical disturbance of the soil because disturbance tends to stimulate microbial activity and SOM decomposition. The simplest way to do this is by reducing tillage (ploughing) intensity through reduced or no-till methods in annual crops as well as with the reduction or elimination of tillage through conversion of annual to perennial crops.
These practices have dozens of nuances and combinations on real farms, but they are known because this is traditionally how food was grown on mixed farms where nutrients and carbon circulated around in a nearly closed loop with only the harvest leaving for the market.
So we love soil carbon because it is the glue that holds low-input farms together and, like it or not, many farms will transition back to their traditional low-input systems.
Farmers will need help
Farmers may not be across the science of soil carbon, but they know all about how important it is to their livelihood. Nobody else on the planet is more intimate with the soils on their farm than they are.
But their job and their skill set are to grow food. And they can’t mess with what they know because it is their livelihood.
If they are asked to change from intensive input production to building soil carbon with one or more of the methods, they will need to be sure it works. Sometimes they will need a nudge. Perhaps an incentive to change practices and overcome barriers.
Subsidies are an option, as are market mechanisms that trade carbon credits. Additional revenue streams that can lower the risk of changing production practices, especially the real and perceived yield losses.
And in Paris, an opportunity emerged.
NDCs are a missed opportunity
Nationally Determined Contributions (NDCs), a mechanism for countries to set ambitious, voluntary mitigation commitments and priority actions for climate adaptation, were established as part of the 2015 Paris Agreement of the United Nations Framework Convention on Climate Change (UNFCCC).
There was pressure on national governments to incorporate SOC into their programmes for climate mitigation and adaptation building on an existing international agenda for restoring soil health.
In 2021 a team of researchers asked international, and country experts about country commitments to soil organic carbon in Nationally Determined Contributions.
Was SOC in the frame, taken seriously or not even considered?
After finding that SOC was explicitly addressed by only 15% (28) of the 184 analyzed NDCs, with varying levels of detail and links to mitigation targets, they concluded that the countries with the highest potential for soil carbon protection or sequestration generally did not specify SOC in their NDCs.
Some countries were paying attention through domestic policy mechanisms, the US and the EU, but many lacked technical capacities.
Some countries have kept agriculture off their GHG balance sheet wherever possible because intensive agriculture is a GHG emission source. Adding SOC to their NDC would shine a light into a dark place. Other countries did not see SOC gains as sequestration, more a co-benefit that did not need to be accounted for. This makes sense where the net SOC gains are small relative to the overall NDC. Some countries did not include SOC due to accounting difficulties citing a lack of accurate, affordable data or suitable SOC monitoring, reporting and verification capabilities, especially linking management practices to changes in SOC. Accounting difficulties suggest that more countries would include SOC in their NDCs if these technical issues could be overcome.
Whatever the excuse, 156 countries did not include SOC in their NDC. That smells like a missed opportunity to us.
What sustainably FED suggests
We are often struck by the gap between the farmer and the future. His immediate local challenge is beset with reactive decisions on a daily, sometimes hourly, basis just to keep his operation viable.
The future barely stretches beyond the current season.
Nations must take a longer view. Note that we said nations and not politicians these days. They are on a stupidly short, narcissistic cycle that makes the farmers look like seers.
Nations must look long because this is the organisational scale that has the freedom to do it. Most either human social constructions and especially individuals are too busy keeping up with the moment.
We suggest that the next NDCs should all have SOC in the mix.
This means talking again to all the experts and advisors and reminding them of how important it will be to pull all the levers available that help returns carbon back into the soil.
Science source
Alexander, P., Paustian, K., Smith, P., & Moran, D. (2015). The economics of soil C sequestration and agricultural emissions abatement. Soil, 1(1), 331-339.
Wiese, L., Wollenberg, E., Alcántara-Shivapatham, V., Richards, M., Shelton, S., Hönle, S. E., … & Chenu, C. (2021). Countries’ commitments to soil organic carbon in Nationally Determined Contributions. Climate Policy, 21(8), 1005-1019.
Hero image from photo by Glen Carrie on Unsplash
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