Annual green water resources and vegetation resilience indicators: definitions, mutual relationships and future climate projections

Abstract

Satellites offer a privileged view on terrestrial ecosystems and a unique possibility to evaluate their status for estimating the reliability of the ecosystem services they provide. We implement an indicator measuring the stability of annual vegetation productivity at the global scale based on the Normalized Differential Vegetation Index (NDVI) that can be used as a proxy of ecosystem services reliability. This indicator, originally developed in agricultural science, is defined as the squared mean of annual crop production divided by its variance. The resilience indicator is proportional to the return periods of system failure by extreme drought events consistently with the ecological definition of resilience. Here, we implement it on annual precipitation and NDVI time-series, as proxies of green water resources and of vegetation primary production, respectively. We find coherent relationships between annual green water resources resilience and vegetation primary production resilience over a wide range of world biomes. Finally, we estimate the changes of green water resources resilience due to climate change using preliminary results from the upcoming Sixth edition of the Coupled Model Inter-comparison Project (CMIP6) and discuss the potential consequences of global warming for ecosystem service reliability.