The mosaic of forest and savanna vegetation found along the northern margin of West Africa's moist forest zone has generally been understood in policy circles as a degraded and degrading forest landscape, following savannisation by its farming populations. Some ecologists have suggested that the vegetation mosaic may, however, be more stable, determined by soil differences, and others still that forest may be encroaching on savanna as a result of long-term climatic rehumidification. This article presents historical evidence from Kissidougou which shows that, contrary to scientific and policy orthodoxy there, forest areas have been increasing at the expense of savanna in recent times. The article outlines the local agro-ecological practices which have been enriching the landscape, and examines how the observed course of vegetation change this century can be accounted for in the articulation of these practices with political, economic, demographic and climatic changes. A retheorisation of ecology in the forest-savanna mosaic is offered which, in drawing on non-equilibrium dynamics, offers a better framework for understanding people's impact on forest-savanna ecology.