• Energy Research

The ‘4 per mille Soils 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 sequestration potentials 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 mille initiative is feasible for the region. The outcomes highlight region specific efforts and scopes for soil carbon sequestration. Reported soil C sequestration rates globally show that under best management practices, 4 per mille or even higher sequestration rates can be accomplished. High C sequestration rates (up to 10 per mille) can be achieved for soils with low initial SOC stock (topsoil less 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 sequestration only consider topsoil (up to 0.3 m depth), as it is considered to be most affected by management techniques. The 4 per mille number 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 mille in the top 1m of global agricultural soils, SOC sequestration is 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 sequestration buys time over the next ten to twenty years while other effective sequestration and 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 mille requires collaboration and communication between scientists, farmers, policy makers, and marketeers.

How climate change will affect spatial coherence of droughts is a key question that water managers must answer in order to adopt strategies to mitigate impacts on water resources. For example, water transfers between regions have long been considered as a possible water management option. Conjunctive use of surface water and groundwater is another common water management practice. However, in both cases, these solutions are only viable if both regions or stores are not in drought simultaneously. These relationships might change under the influence of climate change.The recently published ‘enhanced Future Flows and Groundwater’ (eFLaG) dataset of nationally consistent hydrological projections for the UK, based on the latest UK Climate Projections (UKCP18), provides the opportunity to explore the future evolution of drought spatial coherence in detail. Here, we use eFLaG future simulations of streamflows and groundwater levels to analyse the projected change in drought spatial coherence in Great Britain, over its seven different water regions, using joint and conditional probabilities of occurrence. Some key findings are: an increase in coherence in summer everywhere in the country; in winter, however, it will only increase in the South-East; and, in most regions, the coherence between groundwater and streamflow droughts will increase, one exception being the South-East in summer.These results provide valuable insight to water managers to inform their long-term strategies to overcome future impacts of droughts. The methodology has the potential to be applied to other parts of the world to help shape strategic regional and national investments to increase resilience to droughts.