SAHELIAN RANGELAND DEVELOPMENT - A CATASTROPHE

This paper sets out that the dynamics of the Sahelian rangeland vegeta tion can be interpreted as a cusp catastrophe and that this interpreta tion offers a promising basis for the description and analysis of this ecosystem, Firstly, an existing scheme of the dynamics of Sahelian he rbaceous vegetation is translated into the state-and-transition formul ation, Secondly, the application of the cusp catastrophe is explored b y studying the behaviour of the Sahelian rangeland ecosystem under cha nging effective rainfall and grazing intensity, using the transitions from the state-and-transition formulation as vectors along the cusp ma nifold, This conceptual cusp catastrophe model subsequently results in the identification of hypotheses and the detection of 5 catastrophic properties of this ecosystem (bimodality, inaccessibility, sudden jump s, divergence and hysteresis) that have important management implicati ons, The continuous and the discontinuous processes occurring in the S ahelian rangeland ecosystem can both be captured in a unified conceptu al model by applying the cusp catastrophe theory, Testing the hypothes es generated by the conceptual model and searching for additional cata strophic properties, such as divergence of linear response and critica l slowing down, is a useful direction for future research.