Livestock management promotes bush encroachment in savanna systems by altering plant-herbivore feedback

This repository contains all code to reproduce the analysis in Koch et al. 2022 "Livestock management promotes bush encroachment in savanna systems by altering plant-herbivore feedback".

We use a set of coupled differential equations to describe competition between shrubs and grasses, as well as plant biomass consumption via grazing and browsing. Grazers were assumed to receive a certain level of care from farmers, so that grazer densities emerge dynamically from the combined effect of vegetation abundance and farmer
support. Our main goal was to understand how critical transitions from grass-dominated to shrub-dominated system states were affected by the dynamic role of grazing.

Our results show that bistability emerges for intermediate levels of farmer support due to positive feedback that arises from competition between shrubs and grasses and from herbivory. We furthermore demonstrate that disturbances, such as drought events, trigger abrupt transitions from the grass dominated to the shrub dominated state and that the system becomes more susceptible to disturbances with increasing farmer support.