Soil is in a Self-Organised Critical State with a Tipping Point Driven by Carbon

Abstract

Unsustainable practices are degrading over 40% of global agricultural soils, which in turn is driving climate change, biodiversity loss, and food and water insecurity at a planetary scale. We don’t know if further degradation will be proportionate or if there is a tipping point that will result in catastrophic loss of function. While increasing soil organic carbon stocks can restore soil functions, there is a lack of consensus on how carbon levels can be maintained, and we don’t understand how soil carbon impacts soil function. These uncertainties are the most significant barriers to investing in soil at the necessary scale and pace. Here, we develop and test a mechanistic theory that the soil system is in a self-organised critical state with a critical, or ‘tipping’, point driven by organic carbon. The parameters of the dynamical state are independent of time and management but depend on soil texture. While tillage and reduced input of carbon push soils toward this tipping point, we show the primary consequence of the self-organised critical state is maintaining functional resilience when carbon inputs fluctuate. We discuss how this dynamic state relates to the concept of soil health and the means to measure and restore it at scale.