Concern about desiccation – the effects of deforestation on climate and soils – was an early and pervasive theme in colonial science, present at the onset of West Africa's colonial era and with roots in previous centuries. As a set of scientists' ideas linked to soil and forest conservation policy, the impact of desiccationism was initially muted, struggling unsuccessfully in nascent administrations with more pressing political and administrative agendas. But by the end of the colonial period it can be argued that anxiety about desiccation had become a cornerstone of development practice and state penetration. This article uses a case study to consider the transformation of the status of the ‘science’ of desiccation within colonial development agendas, the responses this transformation eventually provoked and its enduring legacy.

Our reflections here complement what has, in West African studies, become a general consensus about shifts in colonial forest policy. From the outset, many colonial administrations – both francophone and anglophone – were concerned both about the effects of forest loss on climate, hydrology and soils, and about the effects of ‘irrational and wasteful’ exploitation of forest as an economic resource. But early policy imperatives to establish reserves either failed to reach the implementation stage or could not be implemented due to the resistance they engendered, both from populations and indeed from agricultural or political administrations. A significant phase of reservation, at least in West Africa's humid forest and transition zones, began only in the late 1920s and early 1930s, and was pursued until the mid 1950s by colonial states which increasingly gained the strength to impose unpopular policy despite resistance. From this perspective, and given that nationalist sentiments in pre-independence struggles were often pitted against repressive colonial forest services, it could be hypothesized that independence would bring regimes more responsive to local concerns and more likely to heed resistance. Yet such a view, focusing simply on state capacity in changing political contexts, overlooks qualitative changes in the configuration of science-policy relationships within the state, a reconfiguration that it is necessary to grasp if we are to understand how post-colonial forest policy was less a rupture than a continuation or, indeed, reinforcement.