Modelling interacting plant and livestock renewal dynamics helps disentangle equilibrium and nonequilibrium aspects in a Mongolian pastoral system

Abstract

The interplay of livestock density dependence drivers and climate hazards is thought to cause pasture deterioration and poverty in Mongolian pastoral systems. We assessed their relative weights in a system of the Gobi exposed to high rainfall variability and harsh winters, which suggests that climate is the main system's driver. In this aim we modelled how interacting plant and livestock renewal dynamics impact herder performances, under the influence of climate. Plant dynamics was studied through an underground biomass sub-model because local pastures are dominated by perennial species. This approach enabled us studying pastoral issues in a holistic way, by integrating plant underground organs, livestock populations, herder income, and climate drivers. Models described that current grazing practices can significantly reduce underground biomass (−30% after 20years), but not entirely deplete it. They also showed that competition between herders could trap the smallest ones in poverty, by preventing the growth of their herds. This competition operates through density dependent factors affecting livestock productivity and vulnerability to climate shocks. This competition effect is all the more important since small herders could grow their herd and escape poverty if they were alone in the system. This result shows that density dependent factors could significantly impact herder performances and suggests that forage resource allocation is a driver as powerful as climate, even in the local harsh bioclimatic configuration of the Mongolian Gobi.