A Dynamical System Approach to Aridity and Desertification

A large-scale view of arid regions often shows that the vegetation grows in patterns. These are related to the amount of precipitation as well as to the topography. A model is presented that reproduces the wide range of patterns observed in water-limited regions, from bare soil at very low precipitation to uniform cover at high precipitation, through intermediate states of spot-, stripe-and hole-patterns. The model pre- dicts the coexistence of more than one stable state in a given range of precipitation. The results of the model lead to an understanding of the hysteretic nature of desertification, and to a new approach to the classification of aridity.