November 2022 was a watershed moment when the world population crossed 8 billion. In 2011 the world population was 7 billion and by 2050 it is expected to touch 9.8 billion. The world’s population more than tripled between 1950 and 2020. More than half of the projected increase in the global population up to 2050 will be concentrated in eight countries: the Democratic Republic of the Congo, Egypt, Ethiopia, India, Nigeria, Pakistan, the Philippines and Tanzania. Countries of sub-Saharan Africa are expected to contribute more than half of the increase anticipated through 2050.
Agricultural production must ramp up to feed a growing population. This can be achieved either by bringing more land under cultivation or through ''sustainable intensification", that is by closing yield gaps on under-performing lands. However, the first option, converting forests and grasslands to cropland, releases the stored carbon thus contributing to climate change. The Global Carbon Budget 2022 report released during the COP27 deliberations in Egypt showed that carbon dioxide emissions from land use changes is projected to be 3.9 billion tons in 2022. Therefore, in light of the Paris climate accords and the fact that emissions are already at unsustainable levels (total 40 billion tons in 2022), it is clear that pursuing the land use conversion route will only aggravate the climate crisis.
How can agriculture feed 9.8 billion people by 2050 and yet contribute to mitigating climate change. The answer lies in viewing soils in a different light. The concept of “negative emissions technology”, essentially removing and sequestering carbon dioxide from the air, has been gaining ground. Recent analyses suggest that deploying negative emissions technologies may be less expensive and less disruptive than reducing certain kinds of emissions. With other technologies such as bioenergy with carbon capture and storage, and afforestation, soil carbon sequestration is one of the main approaches to carbon removal and storage. Scientists have estimated that soils—mostly, agricultural ones—could sequester over a billion tons of carbon each year. Part of the attraction of soil carbon sequestration is that increases in soil carbon content are highly beneficial in enhancing soil health and soil fertility leading to improved crop yields.
Research studies and modelling by ICRISAT have shown that different management practices like addition of crop residue, addition of biochar, minimum tillage, intercropping, growing cover crops, ploughing of green manure, among others lead to increase in the soil organic carbon stock.
Improved agronomic practices have been shown to have a significant environmental impact (carbon sequestration) as well as improving yields and increasing profits of smallholder farmers. Other studies have indicated that a variety of conservation management practices used in conjunction can result in removal of 2 to 5 billion tons of carbon per year. Higher estimates take into account management of grazing lands in addition to croplands.
Nearly half of the world’s agricultural land (44%) is located in drylands, mainly in Africa and Asia, and supplies about 60% of the world’s food production. Drylands are specially vulnerable to climate change leading to degradation and eventually to desertification. To convert agricultural lands to net carbon sinks in the drylands will not be easy as millions of farmers in the drylands cultivate small plots of land.
To take full advantage of soil-based carbon sequestration as a climate solution, we would need these millions of farmers to change the way they farm, now and years in the future. This is a major social and economic challenge with no easy solutions.
As the science of carbon sequestration is in its early days, another challenge to overcome is monitoring, verifying, and quantifying carbon sequestration. This is as an important area to address in order to boost accountability in this growing space.
In policy and decision making circles there is a growing realisation of the contribution of agriculture to mitigating climate change. The “4 per 1000” initiative launched by France at COP21 aims to demonstrate that agriculture can play a crucial role in mitigating climate change. The initiative aims to increase by 0.4% (or 4 per thousand) per year the amount of carbon sequestered in the top 30 to 40 cm of soil, to offset the annual increase of carbon dioxide in the atmosphere.
Though soil carbon sequestration at scale, sufficient to mitigate climate change, is enormously challenging in sub-Saharan Africa which has poor, degraded soils, to keep the momentum going, stakeholders in the agriculture ecosystem must (i) develop science-based scalable solutions suitable for sub-Saharan Africa and other dryland regions of the world, and (ii) engage with policy makers to design policy incentives for farmers to switch to nature-positive conservation management practices.