Dirt Simple

Fixing more carbon in soil: no labcoats required

Gavin MacRae

Photo by Carsten Frenzl, CC, cropped from original

Climate change mitigation requires serious innovation. We need a major development in fusion, or a quantum leap in solar cells, or a stunning advance in battery storage, right?

Time to stop and take a look at the ground beneath our feet.

The earth’s soils hold two to three times more carbon than the atmosphere. A minuscule increase in the amount of carbon that soil already locks down in the ground would tip the scales back toward climate stabilization.

This is the goal of the “4 Per 1000” initiative. Spearheaded by France in 2015, 4 per 1000 is based around one surprising (and very encouraging) finding: a 0.4% increase in the rate of carbon storage in the top 30 to 40 centimetres of the world’s soil would stop the increase of carbon dioxide in the atmosphere.

The ways to do this are decidedly low tech – no cutting-edge research, no machinery to suck CO2 from the sky – just basic changes to agriculture, land management, and forestry practices.

Plants remove 30% of the carbon dioxide from the atmosphere. When plant life dies, bacteria, fungi, and invertebrates break down the plant matter. This releases most of the carbon back to the atmosphere to repeat the cycle, but some carbon remains trapped in the soil. Amassing more of this carbon-rich soil sequesters more carbon.

4 per 1000 is based around one surprising finding: a 0.4% increase in the rate of carbon storage in the top 30 to 40 centimetres of the world’s soil would stop the increase of carbon dioxide in the atmosphere.

A prerequisite of the 4 per 1000 initiative is halting deforestation. Forests cleared for slash-and-burn agriculture or timber not only lose the carbon stored in vegetation, but lower the carbon holding capacity of the soil. Reforestation and agroforestry (planting trees and shrubs in and around cropland) can build back these wasted soils.

Conservation agriculture and landscape management are central to the initiative. A handful of uncomplicated practices can rebound soil health: avoiding bare soils on croplands, using manure and compost as soil amendments, and allowing water to collect at the base of plants.
The estimated cost of restoring soils on agricultural land runs about $24 per hectare. The effects, if maintained, last two to three decades. With 570 million farms worldwide and three billion people living in rural areas, there is no shortage of manpower.

Of course, with climate change, there is always a catch. Research from 2016 published in Nature shows increased temperatures could invigorate soil microbes that would release additional CO2 , potentially equivalent to the emissions of the United States. That in turn will increase temperatures that… you get the idea. This frightening domino effect underscores the need for soil carbon storage to take the limelight in climate mitigation efforts.

Climate aside, with a projected 9.8 billion mouths to feed by 2050, 4 Per 1000 is a good idea. Sufficient organic matter is the main indicator of soil health, and soil degradation threatens over 40% of the earth’s land surface. Threats to soil are threats to food security.

4 Per 1000 is open ended: national, regional, and local governments can join. So can farming and forestry organizations, private agricultural and forestry companies, NGOs, and other civil society organizations.


Gavin MacRae is the Watershed Sentinel’s staff reporter and editorial assistant. He lives in Comox, BC.

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