Abstract

This paper traces how quantitative science was mobilised in response to one of the greatest modern environmental crises: the global, human-caused mass extinction of animals and plants. For conservation measures it was essential to know what organisms were extinct, threatened, merely rare, or relatively safe from threat. In the 1960s the International Union for the Conservation of Nature (IUCN) began compiling and publishing its Red Data Books of threatened species. From the 1970s the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) began listing endangered species for which trade in products would be regulated. This paper will argue, firstly, that the criteria of the IUCN ’s categories of threat were reformulated in the 1990s on the basis of quantitative population biology. The justification of this being a more ‘objective’ and practical approach was disputed by critics. Secondly, a combination of the championing of the quantitative approach by the IUCN and the trade agendas of Southern African countries led to a similar redefinition of the CITES criteria. Considered as a whole, these episodes present rich case studies in the advantages and disadvantages of appealing to quantitative science to aid international governance.