By better managing farmland soil, the amount of carbon stored in the top 30 centimeters of the soil could increase an extra 0.9 to 1.85 gigatons each year, say authors of a new study published today in Scientific Reports.
This is equivalent to carbon globally emitted by the transport sector (1.87 gigatons of Carbon); and equivalent to 3 – 7 billion tonnes of CO2 which could be removed from the atmosphere. For comparison, the US emits 5 billion tonnes of CO2 equivalent each year (Edgar database, 2015).
The maps in the new study show how much carbon could be stored per hectare each year, which will be vital for designing global mitigation strategies, for achieving targets set out in the Paris Climate Agreement.
Since the industrial revolution, 50-70 percent of carbon stored in the soil has been lost to the atmosphere, contributing to harmful greenhouse gas emissions in the form of carbon dioxide. Since farmland is already intensively managed, improving the way it is managed is a practical step to reduce carbon in the atmosphere, say authors.
Soil organic carbon (SOC) in the top 30 cm, currently (T0), on all available cropland soils globally (i.e. those not excluded from the analysis as high SOC soils or sandy soils). Maps were produced based upon a geospatial analysis of datasets from the SoilsGrids250 database19, using ESRI ArcGIS software (version 10.3; www.esri.com).
Dr. Robert Zomer, from the Kunming Institute of Botany, Chinese Academy of Sciences and lead-author of the study, said: “Our finding show that turning soils into carbon sinks can sequester significant amounts of carbon in cropland soils. Our research shows soils can be part of the solution to combat climate change – and by doing so we can improve soil health.
The findings illustrate that most of the world’s carbon is stored in cooler, wetter, parts of the world in the northern hemisphere; and less in the tropics where it is hotter or drier. North America, Russia and Europe currently store for over half of the world’s carbon in croplands.
The United States showed the highest total annual potential to store carbon in the soil, followed by India, China, Russian and Australia, if management is improved. The improved practices, among others, include, using compost or (green) manure, mulching, zero tillage, cover cropping, and other regenerative and natural climate solutions, such as agroforestry.
Annual increase in soil organic carbon (SOC) in the top 30 cm, on all available cropland soils globally (i.e. those not excluded from the analysis as high SOC or sandy soils) under the medium scenario (i.e. an increase in percent SOC of 0.27 over 20 years). Maps were produced based upon a geospatial analysis of datasets from the SoilsGrids250 database19, using ESRI ArcGIS software (version 10.3; www.esri.com).
“Regenerating soil organic carbon is a foundational strategy for conservation, through which we can provide food and water sustainably and help tackle climate change. Analyses like this help us understand the importance of soil management for reaching climate goals. The question now is: how can we unlock this potential?” asked Dr. Deborah Bossio, Lead Soil Scientist at The Nature Conservancy.
Tropical soils are especially sensitive to management, as they lose carbon faster than their counterparts in temperate regions, due to higher temperatures and rainfalls. Dr. Rolf Sommer, CIAT’s principle soil scientist and part of the CGIAR Research Program on Water, Land and Ecosystems, which funded the study said:
“In western Kenya, over half of all carbon stored in the soil has been released to the atmosphere in the last 30-100 years. That’s roughly twice the speed we would see in other parts of the world like in parts of Europe.”
The authors point out that further research is needed to pin-point which soil management practices are possible in specific areas to sequester more carbon. Especially in developing countries like Ethiopia, where carbon sequestration in soils could significantly reduce emissions and make agriculture carbon neutral, farmers are often very resource constrained, with few options to actively manage soils.