Acknowledgements Thanks to Steve J. Davis who created the original figures from which the figures presented here were adapted. This output contributes to the Belmont Forum/FACCE-JPI funded DEVIL project (NE/M021327/1), the Global Carbon Project and the MaGNET programme (http://www.cger.nies.go.jp/gcp/magnet.html), and also contributes to the EU FP7 SmartSoil project (project number: 289694).Peer reviewedPostprin