Soil is the biggest terrestrial carbon sink. The world’s soils store more carbon than the planet’s biomass and atmosphere combined. This includes soil organic carbon, which is essentially biodiversity: microbes, fungi and invertebrates, as well as root matter and decomposing vegetation. Soil carbon stocks can be increased through appropriate land management to provide many benefits besides offsetting greenhouse gas emissions.

Loss of soil organic carbon is one of the principal signs of land degradation, and land degradation is one of the leading challenges for sustainable development, biodiversity conservation, and mitigating and adapting to climate change. It is defined as a reduction or loss of the biological or economic productivity and complexity of land. In drylands, land degradation is known as desertification.

When land is degraded, soil carbon can be released into the atmosphere, along with nitrous oxide, making land degradation one of the biggest contributors to climate change. An estimated two-thirds of all terrestrial carbon stores from soils and vegetation have been lost since the 19^th century through land degradation. Agriculture, forest and other land-use sectors generate roughly a quarter of all anthropogenic greenhouse gas emissions.

A broad suite of agro-ecology practices can be used to increase carbon in the soil, including agroforestry, fallows (resting soil for a year or more), and sustainable pasture management through managed herd mobility. In many countries these are known – and even Indigenous – practices that can be revived with the right support.

Recent studies suggest that soil carbon management presents one of the most cost-effective climate change mitigation options. Rangelands, for example, contain more than a third of all the terrestrial above- and below-ground carbon reserves. With improved rangeland management they could potentially sequester a further 1,300-2,000 million metric tons of CO₂ by 2030.

Small increases in global soil organic carbon will have a high impact on the global carbon cycle and on the atmospheric concentration of CO₂. An increase of just 1% of the carbon stocks in the top metre of soils would be higher than the amount corresponding to the annual anthropogenic CO₂ emissions from fossil fuel burning. Reversing land degradation and increasing soil organic carbon provides one of the surest and lowest-cost multiple-wins: climate change mitigation and adaptation, conservation of biodiversity, and increased food production.