Building on multisited ethnographic case studies, this paper seeks to contrastively compare the demonstration and articulation formats of two social science expert cultures—economics and anthropology—enrolled ‘in the wild’ of transnational environmental politics. How, the paper asks, do different social sciences come to be configured within, and do performative work upon, heterogeneous assemblages of global natures? In the first case US economists translate carbon markets into a world of Indian ecoprofessionals, across serious North–South conflicts in climate politics. In the second case a group of anthropologists, mobilized by Japanese bureaucratic elites, deploy their methods to assemble whaling cultures, as part of global biodiversity conflicts. Whereas the first case builds on existing arguments on the ‘performativity of economics' (Callon), the second case expands this agenda, noting how the noneconomic social sciences (eg, anthropology) may also be consequential in enacting particular nature-cultures. Theoretically, the paper situates these inquiries at the intersection of science and technology studies (STS) and political anthropology, in addressing the question—important to environmental expertise and politics—of how ‘local’ (particular) and ‘global’ (universal) claims are linked in efficacious ways in ‘other-than-Western’ contexts? Here, the argument will be that, despite their differences, economic and anthropological performances of global natures share certain formal (aesthetic) similarities, related to credible expert demonstrations in transnational environmental contexts. The paper concludes by discussing the implications of this claim for STS self-reflection on its politics of methods.