The recent debate about the sustainability of African pastoralism is taken to illustrate four general issues in environmental management: (i) the extent to which the institutionalization of environmental paradigms has made them conform to the Kuhnian model; (ii) the intimate link between environmental policies and paradigms; (iii) the need to understand the dialogue between scientists, policy-makers and educators and the environment; and (iv) the theoretical and practical weakness of an environmental science that does not rest on a dialogue with cultural geography. The 'old paradigm' in range ecology depended on three main sets of actors: (i) range ecologists who believed in Clement's (1916) model of succession and ecological stability; (ii) economists who believed in Hardin's (1968) concepts of the 'tragedy of the commons'; and (iii) authoritarian administrations which saw pastoralists as backward and destructive, and which had the power and the structures to use and perpetuate scientific paradigms. The so-called 'new paradigm' sees semi-arid ecosystems as being in permanent disequilibrium but persistent on broad temporal and spatial scales whilst many indigenous pastoral strategies are carefully adapted to these characteristics. Keywords: grazing, commons, overgrazing, carrying capacity, colonialism, nomads, Kuhn, institutionalisation.