As the social dimension and hybridity of environmental problems have become clear, and transformative changes of our societies have been presented as the solution to these problems, the question has arisen of whom expert organizations such as IPCC and IPBES should continue to call on to remain credible, relevant and legitimate. To explore and explain different dimensions of social expertise, this paper formulates and problematizes three potential answers to the question of whom to call upon as an expert on the social. First, to expand the jurisdiction of natural science expertise. Second, to acknowledge the jurisdiction of social science expertise. Third, to embrace the jurisdiction of transdisciplinary expertise. With these answers, the paper explores different perspectives on how to understand social expertise, unveils jurisdictional disputes that are taking place over whom may explain the social dimensions of environmental problems and transformative change, and argues for the importance of a greater and reflexive understanding of different forms of expertise among the actors that carry the responsibility to call on experts on transformative change.