The Sahel region in West Africa has been experiencing a persistent drought throughout the last three decades. Here, we present a new perspective on the underlying physical mechanism behind this phenomenon. We use a coupled biosphere-atmosphere model including explicit representation of ecosystem dynamics to demonstrate that, regardless of the nature of the initial forcing, the natural response of the local grass ecosystem to the dry conditions of the late 1960s played a critical role in maintaining the drought through the following decades. The onset of the drought has been marked by a forced shift from a self-sustaining wet climate equilibrium to a similarly self-sustaining but dry climate equilibrium. ¿ 2000 American Geophysical Union