Soil carbon 4 per mille

The ‘4 per milleSoils for Food Security and Climate’ was launched at the COP21 with an aspiration to increase global soil organic matter stocks by 4 per 1000 (or 0.4 %) per year as a compensation for the global emissions of greenhouse gases by anthropogenic sources. This paper surveyed the soil organic carbon (SOC) stock estimates and sequestrationpotentials from 20 regions in the world (New Zealand, Chile, South Africa, Australia, Tanzania, Indonesia, Kenya, Nigeria, India, China Taiwan, South Korea, China Mainland, United States of America, France, Canada, Belgium, England & Wales, Ireland, Scotland, and Russia). We asked whether the 4 per milleinitiative is feasible for the region. The outcomes highlight region specific efforts and scopes for soil carbon sequestration. Reported soil C sequestrationrates globally show that under best management practices, 4 per milleor even higher sequestrationrates can be accomplished. High C sequestrationrates (up to 10 per mille) can be achieved for soils with low initial SOC stock ( topsoilless than 30 t C ha− 1), and at the first twenty years after implementation of best management practices. In addition, areas which have reached equilibrium will not be able to further increase their sequestration. We found that most studies on SOC sequestrationonly consider topsoil(up to 0.3 m depth), as it is considered to be most affected by management techniques. The 4 per millenumber was based on a blanket calculation of the whole global soil profile C stock, however the potential to increase SOC is mostly on managed agricultural lands. If we consider 4 per millein the top 1m of global agricultural soils, SOC sequestrationis between 2-3 Gt C year− 1, which effectively offset 20–35% of global anthropogenic greenhouse gas emissions. As a strategy for climate change mitigation, soil carbon sequestrationbuys time over the next ten to twenty years while other effective sequestrationand low carbon technologies become viable. The challenge for cropping farmers is to find disruptive technologies that will further improve soil condition and deliver increased soil carbon. Progress in 4 per millerequires collaboration and communication between scientists, farmers, policy makers, and marketeers.