1 On the eve of the World Summit on Sustainable Development, it is timely to assess progress over the ten years since its predecessor in Rio de Janeiro. Loss and degradation of remaining natural habitats has continued largely unabated. However, evidence has been accumulating that such systems generate marked economic benefits, which the available data suggest exceed those obtained from continued habitat conversion. We estimate that the overall benefit: cost ratio of an effective global programme for the conservation of remaining wild nature is at least 100: 1. Humans benefit from wild nature (1) in very many ways – aesthetically and culturally; via the provision of ecological services such as climate regulation, soil formation and nutrient cycling; and from the direct harvest of wild species for food, fuel, fibres an