FAO published its first "Global Assessment of Soil Carbon in Grasslands"

After oceans, soils are the second largest carbon pool on Earth, and they play a vital role in global climate change due to the large amount of carbon currently stored in soil organic matter. Soils can act as both sources and sinks of carbon. Many grasslands, especially those used for animal grazing, contain approximately 20% of the world’s Soil Organic Carbon (SOC). In particular, well-managed grasslands can boost the capacity of soils as carbon sinks thanks to improved management practices, helping countries reach their climate goals. This is recent data that emerged from a new report by the Food and Agriculture Organization of the United Nations, FAO, “Global Assessment of Soil Carbon in Grasslands“, funded by the FAO LEAP, Livestock Environmental Assessment and Performance Partnership.

FAO LEAP is a multi-stakeholder initiative that seeks to improve the environmental sustainability of the livestock sector through harmonised methods, metrics, and data. FAO LEAP leads a joint global initiative to accelerate the sustainable development of the livestock supply chain and to support coherent climate actions while contributing to the achievement of the 2030 Agenda for Sustainable Development and the Paris Agreement.

“Global Assessment of Soil Carbon in Grasslands” is the FAO’s first study to illustrate the state of soil carbon stocks in grassland systems and their potential to sequester soil carbon, highlighting where actions are needed to preserve and increase the soils’ capability to store excess carbon. Rotational, planned or adaptative grazing measures for animals can benefit soil health and help mitigate climate change. The FAO assessment measured the baseline of stocks of SOC, that is, the carbon held within the measurable soil, expressed as a percentage by weight (gC/Kg soil), in semi-natural and managed grasslands and estimated their potential of SOC sequestration. The study found that if the SOC content in the 0–30 cm depth layer of open grasslands increased by 0.3 per cent after 20 years of applying management practices that enhance soil organic carbon sequestration, 0.3 tonnes C/ha per year could be sequestered.

“Assessing the current state of grassland systems and their potential to sequester carbon in the soil is key to better understanding the benefits of grassland services for food security, biodiversity conservation and climate change mitigation – Thanawat Tiensin, Director of FAO’s Animal Production and Health Division, explains – This report provides a comprehensive analysis of the state of carbon stocks and potential offsets in grassland soils in the world. It can also be used as a baseline for future works to enhance soil carbon sequestration through sustainable grazing management”.

According to the study, most of the world’s grasslands have a positive carbon balance, meaning the land is stable or well-maintained. Negative carbon balances were found in East Asia, Central and South America, and Africa south of the Equator, meaning these stocks will likely decrease due to anthropogenic stresses combined with climatic conditions. This trend, however, could be reversed by stimulating plant growth, capturing carbon in the soil, and protecting carbon in highly organic soils, such as semi-natural grasslands. This could also mean implementing rotational, planned or adaptative animal grazing measures in livestock management.

The report also explores possible measures to improve SOC stocks, such as establishing fodder gardens in  East African countries. For example, more than 40,000 small farms in Kenya and Uganda have established gardens with Calliandra trees to increase milk production and improve cow health. The trees have shown remarkable success in conserving soil, nutrient cycling, and nutrient retention. According to the study, establishing these gardens has a potential increase in soil carbon of 0.03 tonnes C/ha per year. Also, the grazing systems intensification has been explored in the report, with enhancing carbon inputs from plant roots and residues by managing plant biomass removal from grazing or increasing forage production through improved species, irrigation and fertilisation.

But the lack of incentives for farmers to improve management practices and the difficulty in accurately monitoring SOC stocks and changes are the main reasons that SOCs are not included in the national climate plans NDCs, “National Determined Contributions”, in the Paris Agreement. For this reason, the report’s results could support the inclusion of SOC targets in NDCs. “It is crucial to generate local datasets, especially from underrepresented regions, such as Africa, and explore differences among existing datasets”, the authors warned, since the SOC stocks presented in the report should be used as a baseline for future work to explore the impacts of livestock management on soil carbon at country and farm levels.