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Center for Nonlinear Studies |
Desertification is defined as loss of biological productivity induced by climatic changes and human intervention. From a dynamical-system point of view, desertification is often viewed as an abrupt transition occurring across a saddle-node bifurcation. This simple tipping-point view overlooks two generic aspects of dryland ecosystems: (i) their spatial extent and the often localized form of desertification transitions, (ii) resonant response to seasonal weather variations. In this talk I will address these two aspects using mathematical models of dryland vegetation. I will discuss gradual desertification that proceeds by front propagation, focusing on the possible roles of front pinning in slowing down desertification, and of longitudinal and transverse front instabilities in reversing it. I will further discuss the existence of damped oscillatory modes in dryland vegetation, their resonant response to seasonal rainfall periodicity, and the possibility of early ecosystem collapse following a period-doubling route to chaos.
Host: Aric Hagberg