Conference Agenda

Savanna ecosystems cover an ever-increasing proportion of the Earth’s surface and house a rapidly growing proportion of the world’s population and livestock. An often overlooked but urgent threat to savannas is posed by the process of woody encroachment, by which woodland encroaches upon grasslands used for livestock production, the principal means of subsistence in these areas. In this paper, we look at the impact of time-constant livestock and fire management on the resilience of savannas against bush encroachment in a well-known dynamic savanna model with tipping points. We contribute to the existing literature by studying the sensitivity of savanna resilience to economic, rather than purely physical, parameters. We find that higher livestock prices incentivize management that lowers the resilience of the system, eventually leading to its collapse. We also find that, under general conditions on the livestock dynamics, the proximity to the tipping point cannot be gleaned from vegetation quality, as it stays constant over livestock prices, while the savanna resilience decreases. Fire use makes the resilience of the savanna against woody encroachment more sensitive to changes in livestock prices if fixed livestock offtake and grazing intensity are chosen optimally.